Rework template handling for function and map lookups

This is a big commit, but it deletes lots of code and simplifies a lot. * Resolving the template funcs at execution time means we don't have to create template clones per site * Having a custom map resolver means that we can remove the AST lower case transformation for the special lower case Params map Not only is the above easier to reason about, it's also faster, especially if you have more than one language, as in the benchmark below: ``` name old time/op new time/op delta SiteNew/Deep_content_tree-16 53.7ms ± 0% 48.1ms ± 2% -10.38% (p=0.029 n=4+4) name old alloc/op new alloc/op delta SiteNew/Deep_content_tree-16 41.0MB ± 0% 36.8MB ± 0% -10.26% (p=0.029 n=4+4) name old allocs/op new allocs/op delta SiteNew/Deep_content_tree-16 481k ± 0% 410k ± 0% -14.66% (p=0.029 n=4+4) ``` This should be even better if you also have lots of templates. Closes #6594
2024-11-07 20:30:36 -05:00 · 2019-12-10 19:56:44 +01:00 · 2019-12-10 19:56:44 +01:00 · a03c631c42
commit a03c631c42
parent 167c01530b
41 changed files with 1194 additions and 1898 deletions
--- a/commands/server.go
+++ b/commands/server.go
@ -16,6 +16,7 @@ package commands
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"net/url"
@ -33,7 +34,6 @@ import (
 	"github.com/pkg/errors"

 	"github.com/gohugoio/hugo/livereload"
-	"github.com/gohugoio/hugo/tpl"

 	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/helpers"
@ -287,7 +287,7 @@ func getRootWatchDirsStr(baseDir string, watchDirs []string) string {
 type fileServer struct {
 	baseURLs      []string
 	roots         []string
-	errorTemplate tpl.Template
+	errorTemplate func(err interface{}) (io.Reader, error)
 	c             *commandeer
 	s             *serverCmd
 }
@ -335,8 +335,7 @@ func (f *fileServer) createEndpoint(i int) (*http.ServeMux, string, string, erro
 				err := f.c.getErrorWithContext()
 				if err != nil {
 					w.WriteHeader(500)
-					var b bytes.Buffer
-					err := f.errorTemplate.Execute(&b, err)
+					r, err := f.errorTemplate(err)
 					if err != nil {
 						f.c.logger.ERROR.Println(err)
 					}
@ -344,7 +343,7 @@ func (f *fileServer) createEndpoint(i int) (*http.ServeMux, string, string, erro
 					if !f.c.paused {
 						port = f.c.Cfg.GetInt("liveReloadPort")
 					}
-					fmt.Fprint(w, injectLiveReloadScript(&b, port))
+					fmt.Fprint(w, injectLiveReloadScript(r, port))

 					return
 				}
@ -422,11 +421,15 @@ func (c *commandeer) serve(s *serverCmd) error {
 	}

 	srv := &fileServer{
-		baseURLs:      baseURLs,
-		roots:         roots,
-		c:             c,
-		s:             s,
-		errorTemplate: templ,
+		baseURLs: baseURLs,
+		roots:    roots,
+		c:        c,
+		s:        s,
+		errorTemplate: func(ctx interface{}) (io.Reader, error) {
+			b := &bytes.Buffer{}
+			err := c.hugo().Tmpl.Execute(templ, b, ctx)
+			return b, err
+		},
 	}

 	doLiveReload := !c.Cfg.GetBool("disableLiveReload")
--- a/create/content_template_handler.go
+++ b/create/content_template_handler.go
@ -129,7 +129,7 @@ func executeArcheTypeAsTemplate(s *hugolib.Site, name, kind, targetPath, archety
 	archetypeTemplate = []byte(archetypeShortcodeReplacementsPre.Replace(string(archetypeTemplate)))

 	// Reuse the Hugo template setup to get the template funcs properly set up.
-	templateHandler := s.Deps.Tmpl.(tpl.TemplateHandler)
+	templateHandler := s.Deps.Tmpl.(tpl.TemplateManager)
 	templateName := "_text/" + helpers.Filename(archetypeFilename)
 	if err := templateHandler.AddTemplate(templateName, string(archetypeTemplate)); err != nil {
 		return nil, errors.Wrapf(err, "Failed to parse archetype file %q:", archetypeFilename)
@ -138,7 +138,7 @@ func executeArcheTypeAsTemplate(s *hugolib.Site, name, kind, targetPath, archety
 	templ, _ := templateHandler.Lookup(templateName)

 	var buff bytes.Buffer
-	if err := templ.Execute(&buff, data); err != nil {
+	if err := templateHandler.Execute(templ, &buff, data); err != nil {
 		return nil, errors.Wrapf(err, "Failed to process archetype file %q:", archetypeFilename)
 	}

--- a/deps/deps.go
+++ b/deps/deps.go
@ -37,8 +37,8 @@ type Deps struct {
 	// Used to log warnings that may repeat itself many times.
 	DistinctWarningLog *helpers.DistinctLogger

-	// The templates to use. This will usually implement the full tpl.TemplateHandler.
-	Tmpl tpl.TemplateFinder `json:"-"`
+	// The templates to use. This will usually implement the full tpl.TemplateManager.
+	Tmpl tpl.TemplateHandler `json:"-"`

 	// We use this to parse and execute ad-hoc text templates.
 	TextTmpl tpl.TemplateParseFinder `json:"-"`
@ -77,7 +77,10 @@ type Deps struct {
 	OutputFormatsConfig output.Formats

 	templateProvider ResourceProvider
-	WithTemplate     func(templ tpl.TemplateHandler) error `json:"-"`
+	WithTemplate     func(templ tpl.TemplateManager) error `json:"-"`
+
+	// Used in tests
+	OverloadedTemplateFuncs map[string]interface{}

 	translationProvider ResourceProvider

@ -151,8 +154,8 @@ type ResourceProvider interface {
 }

 // TemplateHandler returns the used tpl.TemplateFinder as tpl.TemplateHandler.
-func (d *Deps) TemplateHandler() tpl.TemplateHandler {
-	return d.Tmpl.(tpl.TemplateHandler)
+func (d *Deps) TemplateHandler() tpl.TemplateManager {
+	return d.Tmpl.(tpl.TemplateManager)
 }

 // LoadResources loads translations and templates.
@ -239,24 +242,25 @@ func New(cfg DepsCfg) (*Deps, error) {
 	distinctWarnLogger := helpers.NewDistinctLogger(logger.WARN)

 	d := &Deps{
-		Fs:                  fs,
-		Log:                 logger,
-		DistinctErrorLog:    distinctErrorLogger,
-		DistinctWarningLog:  distinctWarnLogger,
-		templateProvider:    cfg.TemplateProvider,
-		translationProvider: cfg.TranslationProvider,
-		WithTemplate:        cfg.WithTemplate,
-		PathSpec:            ps,
-		ContentSpec:         contentSpec,
-		SourceSpec:          sp,
-		ResourceSpec:        resourceSpec,
-		Cfg:                 cfg.Language,
-		Language:            cfg.Language,
-		Site:                cfg.Site,
-		FileCaches:          fileCaches,
-		BuildStartListeners: &Listeners{},
-		Timeout:             time.Duration(timeoutms) * time.Millisecond,
-		globalErrHandler:    &globalErrHandler{},
+		Fs:                      fs,
+		Log:                     logger,
+		DistinctErrorLog:        distinctErrorLogger,
+		DistinctWarningLog:      distinctWarnLogger,
+		templateProvider:        cfg.TemplateProvider,
+		translationProvider:     cfg.TranslationProvider,
+		WithTemplate:            cfg.WithTemplate,
+		OverloadedTemplateFuncs: cfg.OverloadedTemplateFuncs,
+		PathSpec:                ps,
+		ContentSpec:             contentSpec,
+		SourceSpec:              sp,
+		ResourceSpec:            resourceSpec,
+		Cfg:                     cfg.Language,
+		Language:                cfg.Language,
+		Site:                    cfg.Site,
+		FileCaches:              fileCaches,
+		BuildStartListeners:     &Listeners{},
+		Timeout:                 time.Duration(timeoutms) * time.Millisecond,
+		globalErrHandler:        &globalErrHandler{},
 	}

 	if cfg.Cfg.GetBool("templateMetrics") {
@ -344,7 +348,9 @@ type DepsCfg struct {

 	// Template handling.
 	TemplateProvider ResourceProvider
-	WithTemplate     func(templ tpl.TemplateHandler) error
+	WithTemplate     func(templ tpl.TemplateManager) error
+	// Used in tests
+	OverloadedTemplateFuncs map[string]interface{}

 	// i18n handling.
 	TranslationProvider ResourceProvider
--- a/hugolib/alias.go
+++ b/hugolib/alias.go
@ -15,6 +15,7 @@ package hugolib

 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"html/template"
 	"io"
@ -31,27 +32,15 @@ import (
 	"github.com/gohugoio/hugo/tpl"
 )

-const (
-	alias      = "<!DOCTYPE html><html><head><title>{{ .Permalink }}</title><link rel=\"canonical\" href=\"{{ .Permalink }}\"/><meta name=\"robots\" content=\"noindex\"><meta charset=\"utf-8\" /><meta http-equiv=\"refresh\" content=\"0; url={{ .Permalink }}\" /></head></html>"
-	aliasXHtml = "<!DOCTYPE html><html xmlns=\"http://www.w3.org/1999/xhtml\"><head><title>{{ .Permalink }}</title><link rel=\"canonical\" href=\"{{ .Permalink }}\"/><meta name=\"robots\" content=\"noindex\"><meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\" /><meta http-equiv=\"refresh\" content=\"0; url={{ .Permalink }}\" /></head></html>"
-)
-
 var defaultAliasTemplates *template.Template

-func init() {
-	//TODO(bep) consolidate
-	defaultAliasTemplates = template.New("")
-	template.Must(defaultAliasTemplates.New("alias").Parse(alias))
-	template.Must(defaultAliasTemplates.New("alias-xhtml").Parse(aliasXHtml))
-}
-
 type aliasHandler struct {
-	t         tpl.TemplateFinder
+	t         tpl.TemplateHandler
 	log       *loggers.Logger
 	allowRoot bool
 }

-func newAliasHandler(t tpl.TemplateFinder, l *loggers.Logger, allowRoot bool) aliasHandler {
+func newAliasHandler(t tpl.TemplateHandler, l *loggers.Logger, allowRoot bool) aliasHandler {
 	return aliasHandler{t, l, allowRoot}
 }

@ -60,33 +49,27 @@ type aliasPage struct {
 	page.Page
 }

-func (a aliasHandler) renderAlias(isXHTML bool, permalink string, p page.Page) (io.Reader, error) {
-	t := "alias"
-	if isXHTML {
-		t = "alias-xhtml"
-	}
+func (a aliasHandler) renderAlias(permalink string, p page.Page) (io.Reader, error) {

 	var templ tpl.Template
 	var found bool

-	if a.t != nil {
-		templ, found = a.t.Lookup("alias.html")
-	}
-
+	templ, found = a.t.Lookup("alias.html")
 	if !found {
-		def := defaultAliasTemplates.Lookup(t)
-		if def != nil {
-			templ = &tpl.TemplateAdapter{Template: def}
+		// TODO(bep) consolidate
+		templ, found = a.t.Lookup("_internal/alias.html")
+		if !found {
+			return nil, errors.New("no alias template found")
 		}
-
 	}
+
 	data := aliasPage{
 		permalink,
 		p,
 	}

 	buffer := new(bytes.Buffer)
-	err := templ.Execute(buffer, data)
+	err := a.t.Execute(templ, buffer, data)
 	if err != nil {
 		return nil, err
 	}
@ -100,8 +83,6 @@ func (s *Site) writeDestAlias(path, permalink string, outputFormat output.Format
 func (s *Site) publishDestAlias(allowRoot bool, path, permalink string, outputFormat output.Format, p page.Page) (err error) {
 	handler := newAliasHandler(s.Tmpl, s.Log, allowRoot)

-	isXHTML := strings.HasSuffix(path, ".xhtml")
-
 	s.Log.DEBUG.Println("creating alias:", path, "redirecting to", permalink)

 	targetPath, err := handler.targetPathAlias(path)
@ -109,7 +90,7 @@ func (s *Site) publishDestAlias(allowRoot bool, path, permalink string, outputFo
 		return err
 	}

-	aliasContent, err := handler.renderAlias(isXHTML, permalink, p)
+	aliasContent, err := handler.renderAlias(permalink, p)
 	if err != nil {
 		return err
 	}
--- a/hugolib/case_insensitive_test.go
+++ b/hugolib/case_insensitive_test.go
@ -14,7 +14,6 @@
 package hugolib

 import (
-	"fmt"
 	"path/filepath"
 	"testing"

@ -232,76 +231,3 @@ Page2: {{ $page2.Params.ColoR }}
 		"index2|Site: yellow|",
 	)
 }
-
-// TODO1
-func TestCaseInsensitiveConfigurationForAllTemplateEngines(t *testing.T) {
-	t.Parallel()
-
-	noOp := func(s string) string {
-		return s
-	}
-
-	for _, config := range []struct {
-		suffix        string
-		templateFixer func(s string) string
-	}{
-		//{"amber", amberFixer},
-		{"html", noOp},
-		//{"ace", noOp},
-	} {
-		doTestCaseInsensitiveConfigurationForTemplateEngine(t, config.suffix, config.templateFixer)
-
-	}
-
-}
-
-func doTestCaseInsensitiveConfigurationForTemplateEngine(t *testing.T, suffix string, templateFixer func(s string) string) {
-	c := qt.New(t)
-	mm := afero.NewMemMapFs()
-
-	caseMixingTestsWriteCommonSources(t, mm)
-
-	cfg, err := LoadConfigDefault(mm)
-	c.Assert(err, qt.IsNil)
-
-	fs := hugofs.NewFrom(mm, cfg)
-
-	th := newTestHelper(cfg, fs, t)
-
-	t.Log("Testing", suffix)
-
-	templTemplate := `
-p
-	|
-	| Page Colors: {{ .Params.CoLOR }}|{{ .Params.Colors.Blue }}
-	| Site Colors: {{ .Site.Params.COlOR }}|{{ .Site.Params.COLORS.YELLOW }}
-	| {{ .Content }}
-
-`
-
-	templ := templateFixer(templTemplate)
-
-	t.Log(templ)
-
-	writeSource(t, fs, filepath.Join("layouts", "_default", fmt.Sprintf("single.%s", suffix)), templ)
-
-	sites, err := NewHugoSites(deps.DepsCfg{Fs: fs, Cfg: cfg})
-
-	if err != nil {
-		t.Fatalf("Failed to create sites: %s", err)
-	}
-
-	err = sites.Build(BuildCfg{})
-
-	if err != nil {
-		t.Fatalf("Failed to build sites: %s", err)
-	}
-
-	th.assertFileContent(filepath.Join("public", "nn", "sect1", "page1", "index.html"),
-		"Page Colors: red|heavenly",
-		"Site Colors: green|yellow",
-		"Shortcode Page: red|heavenly",
-		"Shortcode Site: green|yellow",
-	)
-
-}
--- a/hugolib/embedded_shortcodes_test.go
+++ b/hugolib/embedded_shortcodes_test.go
@ -27,7 +27,6 @@ import (
 	"github.com/gohugoio/hugo/deps"

 	qt "github.com/frankban/quicktest"
-	"github.com/gohugoio/hugo/tpl"
 )

 const (
@ -334,18 +333,13 @@ func TestShortcodeTweet(t *testing.T) {

 		cfg.Set("privacy", this.privacy)

-		withTemplate := func(templ tpl.TemplateHandler) error {
-			templ.(tpl.TemplateTestMocker).SetFuncs(tweetFuncMap)
-			return nil
-		}
-
 		writeSource(t, fs, filepath.Join("content", "simple.md"), fmt.Sprintf(`---
 title: Shorty
 ---
 %s`, this.in))
 		writeSource(t, fs, filepath.Join("layouts", "_default", "single.html"), `{{ .Content }}`)

-		buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg, WithTemplate: withTemplate}, BuildCfg{})
+		buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg, OverloadedTemplateFuncs: tweetFuncMap}, BuildCfg{})

 		th.assertFileContentRegexp(filepath.Join("public", "simple", "index.html"), this.expected)

@ -389,18 +383,13 @@ func TestShortcodeInstagram(t *testing.T) {
 			th      = newTestHelper(cfg, fs, t)
 		)

-		withTemplate := func(templ tpl.TemplateHandler) error {
-			templ.(tpl.TemplateTestMocker).SetFuncs(instagramFuncMap)
-			return nil
-		}
-
 		writeSource(t, fs, filepath.Join("content", "simple.md"), fmt.Sprintf(`---
 title: Shorty
 ---
 %s`, this.in))
 		writeSource(t, fs, filepath.Join("layouts", "_default", "single.html"), `{{ .Content | safeHTML }}`)

-		buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg, WithTemplate: withTemplate}, BuildCfg{})
+		buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg, OverloadedTemplateFuncs: instagramFuncMap}, BuildCfg{})

 		th.assertFileContentRegexp(filepath.Join("public", "simple", "index.html"), this.expected)

--- a/hugolib/hugo_modules_test.go
+++ b/hugolib/hugo_modules_test.go
@ -42,10 +42,10 @@ import (
 func TestHugoModules(t *testing.T) {
 	t.Parallel()

-	if hugo.GoMinorVersion() < 12 {
+	if !isCI() || hugo.GoMinorVersion() < 12 {
 		// https://github.com/golang/go/issues/26794
 		// There were some concurrent issues with Go modules in < Go 12.
-		t.Skip("skip this for Go <= 1.11 due to a bug in Go's stdlib")
+		t.Skip("skip this on local host and for Go <= 1.11 due to a bug in Go's stdlib")
 	}

 	if testing.Short() {
--- a/hugolib/hugo_sites.go
+++ b/hugolib/hugo_sites.go
@ -426,8 +426,8 @@ func NewHugoSites(cfg deps.DepsCfg) (*HugoSites, error) {
 	return newHugoSites(cfg, sites...)
 }

-func (s *Site) withSiteTemplates(withTemplates ...func(templ tpl.TemplateHandler) error) func(templ tpl.TemplateHandler) error {
-	return func(templ tpl.TemplateHandler) error {
+func (s *Site) withSiteTemplates(withTemplates ...func(templ tpl.TemplateManager) error) func(templ tpl.TemplateManager) error {
+	return func(templ tpl.TemplateManager) error {
 		if err := templ.LoadTemplates(""); err != nil {
 			return err
 		}
--- a/hugolib/hugo_smoke_test.go
+++ b/hugolib/hugo_smoke_test.go
@ -21,6 +21,27 @@ import (
 	qt "github.com/frankban/quicktest"
 )

+// The most basic build test.
+func TestHello(t *testing.T) {
+	t.Parallel()
+	b := newTestSitesBuilder(t)
+	b.WithConfigFile("toml", `
+baseURL="https://example.org"
+disableKinds = ["taxonomy", "taxonomyTerm", "section", "page"]
+`)
+	b.WithContent("p1", `
+---
+title: Page
+---
+
+`)
+	b.WithTemplates("index.html", `Site: {{ .Site.Language.Lang | upper }}`)
+
+	b.Build(BuildCfg{})
+
+	b.AssertFileContent("public/index.html", `Site: EN`)
+}
+
 func TestSmoke(t *testing.T) {
 	t.Parallel()

--- a/hugolib/page.go
+++ b/hugolib/page.go
@ -480,7 +480,7 @@ func (p *pageState) Render(layout ...string) template.HTML {
 			templ, _ = p.s.Tmpl.Lookup(layout + ".html")
 		}
 		if templ != nil {
-			res, err := executeToString(templ, p)
+			res, err := executeToString(p.s.Tmpl, templ, p)
 			if err != nil {
 				p.s.SendError(p.wrapError(errors.Wrapf(err, ".Render: failed to execute template %q v", layout)))
 				return ""
--- a/hugolib/page__per_output.go
+++ b/hugolib/page__per_output.go
@ -411,10 +411,10 @@ func (t targetPathsHolder) targetPaths() page.TargetPaths {
 	return t.paths
 }

-func executeToString(templ tpl.Template, data interface{}) (string, error) {
+func executeToString(h tpl.TemplateHandler, templ tpl.Template, data interface{}) (string, error) {
 	b := bp.GetBuffer()
 	defer bp.PutBuffer(b)
-	if err := templ.Execute(b, data); err != nil {
+	if err := h.Execute(templ, b, data); err != nil {
 		return "", err
 	}
 	return b.String(), nil
--- a/hugolib/page_test.go
+++ b/hugolib/page_test.go
@ -459,7 +459,7 @@ func TestPageWithDelimiterForMarkdownThatCrossesBorder(t *testing.T) {
 	}

 	cnt := content(p)
-	if cnt != "<p>The <a href=\"http://gohugo.io/\">best static site generator</a>.<sup id=\"fnref:1\"><a href=\"#fn:1\" class=\"footnote-ref\" role=\"doc-noteref\">1</a></sup></p>\n<section class=\"footnotes\" role=\"doc-endnotes\">\n<hr>\n<ol>\n<li id=\"fn:1\" role=\"doc-endnote\">\n<p>Many people say so. <a href=\"#fnref:1\" class=\"footnote-backref\" role=\"doc-backlink\">&#x21a9;&#xfe0e;</a></p>\n</li>\n</ol>\n</section>" {
+	if cnt != "<p>The <a href=\"http://gohugo.io/\">best static site generator</a>.<sup id=\"fnref:1\"><a href=\"#fn:1\" class=\"footnote-ref\" role=\"doc-noteref\">1</a></sup></p>\n<section class=\"footnotes\" role=\"doc-endnotes\">\n<hr>\n<ol>\n<li id=\"fn:1\" role=\"doc-endnote\">\n<p>Many people say so.<a href=\"#fnref:1\" class=\"footnote-backref\" role=\"doc-backlink\">&#8617;</a></p>\n</li>\n</ol>\n</section>" {
 		t.Fatalf("Got content:\n%q", cnt)
 	}
 }
--- a/hugolib/shortcode.go
+++ b/hugolib/shortcode.go
@ -393,7 +393,7 @@ func renderShortcode(

 	}

-	result, err := renderShortcodeWithPage(tmpl, data)
+	result, err := renderShortcodeWithPage(s.Tmpl, tmpl, data)

 	if err != nil && sc.isInline {
 		fe := herrors.ToFileError("html", err)
@ -634,11 +634,11 @@ func replaceShortcodeTokens(source []byte, replacements map[string]string) ([]by
 	return source, nil
 }

-func renderShortcodeWithPage(tmpl tpl.Template, data *ShortcodeWithPage) (string, error) {
+func renderShortcodeWithPage(h tpl.TemplateHandler, tmpl tpl.Template, data *ShortcodeWithPage) (string, error) {
 	buffer := bp.GetBuffer()
 	defer bp.PutBuffer(buffer)

-	err := tmpl.Execute(buffer, data)
+	err := h.Execute(tmpl, buffer, data)
 	if err != nil {
 		return "", _errors.Wrap(err, "failed to process shortcode")
 	}
--- a/hugolib/shortcode_test.go
+++ b/hugolib/shortcode_test.go
@ -36,12 +36,12 @@ import (
 	qt "github.com/frankban/quicktest"
 )

-func CheckShortCodeMatch(t *testing.T, input, expected string, withTemplate func(templ tpl.TemplateHandler) error) {
+func CheckShortCodeMatch(t *testing.T, input, expected string, withTemplate func(templ tpl.TemplateManager) error) {
 	t.Helper()
 	CheckShortCodeMatchAndError(t, input, expected, withTemplate, false)
 }

-func CheckShortCodeMatchAndError(t *testing.T, input, expected string, withTemplate func(templ tpl.TemplateHandler) error, expectError bool) {
+func CheckShortCodeMatchAndError(t *testing.T, input, expected string, withTemplate func(templ tpl.TemplateManager) error, expectError bool) {
 	t.Helper()
 	cfg, fs := newTestCfg()

@ -95,7 +95,7 @@ func TestNonSC(t *testing.T) {
 // Issue #929
 func TestHyphenatedSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {

 		tem.AddTemplate("_internal/shortcodes/hyphenated-video.html", `Playing Video {{ .Get 0 }}`)
 		return nil
@ -107,7 +107,7 @@ func TestHyphenatedSC(t *testing.T) {
 // Issue #1753
 func TestNoTrailingNewline(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/a.html", `{{ .Get 0 }}`)
 		return nil
 	}
@ -117,7 +117,7 @@ func TestNoTrailingNewline(t *testing.T) {

 func TestPositionalParamSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/video.html", `Playing Video {{ .Get 0 }}`)
 		return nil
 	}
@ -131,7 +131,7 @@ func TestPositionalParamSC(t *testing.T) {

 func TestPositionalParamIndexOutOfBounds(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/video.html", `Playing Video {{ with .Get 1 }}{{ . }}{{ else }}Missing{{ end }}`)
 		return nil
 	}
@ -141,7 +141,7 @@ func TestPositionalParamIndexOutOfBounds(t *testing.T) {
 // #5071
 func TestShortcodeRelated(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/a.html", `{{ len (.Site.RegularPages.Related .Page) }}`)
 		return nil
 	}
@ -151,7 +151,7 @@ func TestShortcodeRelated(t *testing.T) {

 func TestShortcodeInnerMarkup(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("shortcodes/a.html", `<div>{{ .Inner }}</div>`)
 		tem.AddTemplate("shortcodes/b.html", `**Bold**: <div>{{ .Inner }}</div>`)
 		return nil
@ -175,7 +175,7 @@ func TestShortcodeInnerMarkup(t *testing.T) {

 func TestNamedParamSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/img.html", `<img{{ with .Get "src" }} src="{{.}}"{{end}}{{with .Get "class"}} class="{{.}}"{{end}}>`)
 		return nil
 	}
@ -190,7 +190,7 @@ func TestNamedParamSC(t *testing.T) {
 // Issue #2294
 func TestNestedNamedMissingParam(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/acc.html", `<div class="acc">{{ .Inner }}</div>`)
 		tem.AddTemplate("_internal/shortcodes/div.html", `<div {{with .Get "class"}} class="{{ . }}"{{ end }}>{{ .Inner }}</div>`)
 		tem.AddTemplate("_internal/shortcodes/div2.html", `<div {{with .Get 0}} class="{{ . }}"{{ end }}>{{ .Inner }}</div>`)
@ -203,7 +203,7 @@ func TestNestedNamedMissingParam(t *testing.T) {

 func TestIsNamedParamsSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/bynameorposition.html", `{{ with .Get "id" }}Named: {{ . }}{{ else }}Pos: {{ .Get 0 }}{{ end }}`)
 		tem.AddTemplate("_internal/shortcodes/ifnamedparams.html", `<div id="{{ if .IsNamedParams }}{{ .Get "id" }}{{ else }}{{ .Get 0 }}{{end}}">`)
 		return nil
@ -216,7 +216,7 @@ func TestIsNamedParamsSC(t *testing.T) {

 func TestInnerSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/inside.html", `<div{{with .Get "class"}} class="{{.}}"{{end}}>{{ .Inner }}</div>`)
 		return nil
 	}
@ -227,7 +227,7 @@ func TestInnerSC(t *testing.T) {

 func TestInnerSCWithMarkdown(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		// Note: In Hugo 0.55 we made it so any outer {{%'s inner content was rendered as part of the surrounding
 		// markup. This solved lots of problems, but it also meant that this test had to be adjusted.
 		tem.AddTemplate("_internal/shortcodes/wrapper.html", `<div{{with .Get "class"}} class="{{.}}"{{end}}>{{ .Inner }}</div>`)
@ -250,7 +250,7 @@ func TestEmbeddedSC(t *testing.T) {

 func TestNestedSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/scn1.html", `<div>Outer, inner is {{ .Inner }}</div>`)
 		tem.AddTemplate("_internal/shortcodes/scn2.html", `<div>SC2</div>`)
 		return nil
@ -262,7 +262,7 @@ func TestNestedSC(t *testing.T) {

 func TestNestedComplexSC(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/row.html", `-row-{{ .Inner}}-rowStop-`)
 		tem.AddTemplate("_internal/shortcodes/column.html", `-col-{{.Inner    }}-colStop-`)
 		tem.AddTemplate("_internal/shortcodes/aside.html", `-aside-{{    .Inner  }}-asideStop-`)
@ -278,7 +278,7 @@ func TestNestedComplexSC(t *testing.T) {

 func TestParentShortcode(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/r1.html", `1: {{ .Get "pr1" }} {{ .Inner }}`)
 		tem.AddTemplate("_internal/shortcodes/r2.html", `2: {{ .Parent.Get "pr1" }}{{ .Get "pr2" }} {{ .Inner }}`)
 		tem.AddTemplate("_internal/shortcodes/r3.html", `3: {{ .Parent.Parent.Get "pr1" }}{{ .Parent.Get "pr2" }}{{ .Get "pr3" }} {{ .Inner }}`)
@ -333,7 +333,7 @@ func TestFigureLinkWithTargetAndRel(t *testing.T) {
 // #1642
 func TestShortcodeWrappedInPIssue(t *testing.T) {
 	t.Parallel()
-	wt := func(tem tpl.TemplateHandler) error {
+	wt := func(tem tpl.TemplateManager) error {
 		tem.AddTemplate("_internal/shortcodes/bug.html", `xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx`)
 		return nil
 	}
@ -564,7 +564,7 @@ title: "Foo"
 		sources[i] = [2]string{filepath.FromSlash(test.contentPath), test.content}
 	}

-	addTemplates := func(templ tpl.TemplateHandler) error {
+	addTemplates := func(templ tpl.TemplateManager) error {
 		templ.AddTemplate("_default/single.html", "{{.Content}} Word Count: {{ .WordCount }}")

 		templ.AddTemplate("_internal/shortcodes/b.html", `b`)
--- a/hugolib/site.go
+++ b/hugolib/site.go
@ -474,7 +474,7 @@ func NewSite(cfg deps.DepsCfg) (*Site, error) {
 // The site will have a template system loaded and ready to use.
 // Note: This is mainly used in single site tests.
 // TODO(bep) test refactor -- remove
-func NewSiteDefaultLang(withTemplate ...func(templ tpl.TemplateHandler) error) (*Site, error) {
+func NewSiteDefaultLang(withTemplate ...func(templ tpl.TemplateManager) error) (*Site, error) {
 	v := viper.New()
 	if err := loadDefaultSettingsFor(v); err != nil {
 		return nil, err
@ -486,7 +486,7 @@ func NewSiteDefaultLang(withTemplate ...func(templ tpl.TemplateHandler) error) (
 // The site will have a template system loaded and ready to use.
 // Note: This is mainly used in single site tests.
 // TODO(bep) test refactor -- remove
-func NewEnglishSite(withTemplate ...func(templ tpl.TemplateHandler) error) (*Site, error) {
+func NewEnglishSite(withTemplate ...func(templ tpl.TemplateManager) error) (*Site, error) {
 	v := viper.New()
 	if err := loadDefaultSettingsFor(v); err != nil {
 		return nil, err
@ -495,8 +495,8 @@ func NewEnglishSite(withTemplate ...func(templ tpl.TemplateHandler) error) (*Sit
 }

 // newSiteForLang creates a new site in the given language.
-func newSiteForLang(lang *langs.Language, withTemplate ...func(templ tpl.TemplateHandler) error) (*Site, error) {
-	withTemplates := func(templ tpl.TemplateHandler) error {
+func newSiteForLang(lang *langs.Language, withTemplate ...func(templ tpl.TemplateManager) error) (*Site, error) {
+	withTemplates := func(templ tpl.TemplateManager) error {
 		for _, wt := range withTemplate {
 			if err := wt(templ); err != nil {
 				return err
@ -1589,7 +1589,7 @@ func (s *Site) renderForLayouts(name, outputFormat string, d interface{}, w io.W
 		return nil
 	}

-	if err = templ.Execute(w, d); err != nil {
+	if err = s.Tmpl.Execute(templ, w, d); err != nil {
 		return _errors.Wrapf(err, "render of %q failed", name)
 	}
 	return
--- a/hugolib/sitemap_test.go
+++ b/hugolib/sitemap_test.go
@ -50,7 +50,7 @@ func doTestSitemapOutput(t *testing.T, internal bool) {

 	depsCfg := deps.DepsCfg{Fs: fs, Cfg: cfg}

-	depsCfg.WithTemplate = func(templ tpl.TemplateHandler) error {
+	depsCfg.WithTemplate = func(templ tpl.TemplateManager) error {
 		if !internal {
 			templ.AddTemplate("sitemap.xml", sitemapTemplate)
 		}
--- a/hugolib/template_engines_test.go
+++ b/hugolib/template_engines_test.go
@ -1,97 +0,0 @@
-// Copyright 2017 The Hugo Authors. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package hugolib
-
-import (
-	"fmt"
-	"path/filepath"
-	"testing"
-
-	"github.com/gohugoio/hugo/deps"
-)
-
-// TODO1
-func TestAllTemplateEngines(t *testing.T) {
-	noOp := func(s string) string {
-		return s
-	}
-
-	for _, config := range []struct {
-		suffix        string
-		templateFixer func(s string) string
-	}{
-		//{"amber", amberFixer},
-		{"html", noOp},
-		//{"ace", noOp},
-	} {
-		config := config
-		t.Run(config.suffix,
-			func(t *testing.T) {
-				t.Parallel()
-				doTestTemplateEngine(t, config.suffix, config.templateFixer)
-			})
-	}
-
-}
-
-func doTestTemplateEngine(t *testing.T, suffix string, templateFixer func(s string) string) {
-
-	cfg, fs := newTestCfg()
-
-	t.Log("Testing", suffix)
-
-	templTemplate := `
-p
-	|
-	| Page Title: {{ .Title }}
-	br
-	| Page Content: {{ .Content }}
-	br
-	| {{ title "hello world" }}
-
-`
-
-	templShortcodeTemplate := `
-p
-	|
-	| Shortcode: {{ .IsNamedParams }}
-`
-
-	templ := templateFixer(templTemplate)
-	shortcodeTempl := templateFixer(templShortcodeTemplate)
-
-	writeSource(t, fs, filepath.Join("content", "p.md"), `
---
-title: My Title 
---
-My Content
-
-Shortcode: {{< myShort >}}
-
-`)
-
-	writeSource(t, fs, filepath.Join("layouts", "_default", fmt.Sprintf("single.%s", suffix)), templ)
-	writeSource(t, fs, filepath.Join("layouts", "shortcodes", fmt.Sprintf("myShort.%s", suffix)), shortcodeTempl)
-
-	s := buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg}, BuildCfg{})
-	th := newTestHelper(s.Cfg, s.Fs, t)
-
-	th.assertFileContent(filepath.Join("public", "p", "index.html"),
-		"Page Title: My Title",
-		"My Content",
-		"Hello World",
-		"Shortcode: false",
-	)
-
-}
--- a/hugolib/testhelpers_test.go
+++ b/hugolib/testhelpers_test.go
@ -845,9 +845,9 @@ func newTestSitesFromConfig(t testing.TB, afs afero.Fs, tomlConfig string, layou
 	return th, h
 }

-func createWithTemplateFromNameValues(additionalTemplates ...string) func(templ tpl.TemplateHandler) error {
+func createWithTemplateFromNameValues(additionalTemplates ...string) func(templ tpl.TemplateManager) error {

-	return func(templ tpl.TemplateHandler) error {
+	return func(templ tpl.TemplateManager) error {
 		for i := 0; i < len(additionalTemplates); i += 2 {
 			err := templ.AddTemplate(additionalTemplates[i], additionalTemplates[i+1])
 			if err != nil {
--- a/langs/language.go
+++ b/langs/language.go
@ -16,6 +16,7 @@ package langs
 import (
 	"sort"
 	"strings"
+	"sync"

 	"github.com/gohugoio/hugo/common/maps"
 	"github.com/gohugoio/hugo/config"
@ -56,7 +57,9 @@ type Language struct {

 	// These are params declared in the [params] section of the language merged with the
 	// site's params, the most specific (language) wins on duplicate keys.
-	params map[string]interface{}
+	params    map[string]interface{}
+	paramsMu  sync.Mutex
+	paramsSet bool

 	// These are config values, i.e. the settings declared outside of the [params] section of the language.
 	// This is the map Hugo looks in when looking for configuration values (baseURL etc.).
@ -123,7 +126,15 @@ func (l Languages) Less(i, j int) bool {
 func (l Languages) Swap(i, j int) { l[i], l[j] = l[j], l[i] }

 // Params retunrs language-specific params merged with the global params.
-func (l *Language) Params() map[string]interface{} {
+func (l *Language) Params() maps.Params {
+	// TODO(bep) this construct should not be needed. Create the
+	// language params in one go.
+	l.paramsMu.Lock()
+	defer l.paramsMu.Unlock()
+	if !l.paramsSet {
+		maps.ToLower(l.params)
+		l.paramsSet = true
+	}
 	return l.params
 }

@ -163,7 +174,12 @@ func (l Languages) IsMultihost() bool {
 // SetParam sets a param with the given key and value.
 // SetParam is case-insensitive.
 func (l *Language) SetParam(k string, v interface{}) {
-	l.params[strings.ToLower(k)] = v
+	l.paramsMu.Lock()
+	defer l.paramsMu.Unlock()
+	if l.paramsSet {
+		panic("params cannot be changed once set")
+	}
+	l.params[k] = v
 }

 // GetBool returns the value associated with the key as a boolean.
--- a/resources/resource_transformers/templates/execute_as_template.go
+++ b/resources/resource_transformers/templates/execute_as_template.go
@ -27,25 +27,27 @@ import (
 type Client struct {
 	rs *resources.Spec

-	textTemplate tpl.TemplateParseFinder
+	templateHandler tpl.TemplateHandler
+	textTemplate    tpl.TemplateParseFinder
 }

 // New creates a new Client with the given specification.
-func New(rs *resources.Spec, textTemplate tpl.TemplateParseFinder) *Client {
+func New(rs *resources.Spec, h tpl.TemplateHandler, textTemplate tpl.TemplateParseFinder) *Client {
 	if rs == nil {
 		panic("must provice a resource Spec")
 	}
 	if textTemplate == nil {
 		panic("must provide a textTemplate")
 	}
-	return &Client{rs: rs, textTemplate: textTemplate}
+	return &Client{rs: rs, templateHandler: h, textTemplate: textTemplate}
 }

 type executeAsTemplateTransform struct {
-	rs           *resources.Spec
-	textTemplate tpl.TemplateParseFinder
-	targetPath   string
-	data         interface{}
+	rs              *resources.Spec
+	textTemplate    tpl.TemplateParseFinder
+	templateHandler tpl.TemplateHandler
+	targetPath      string
+	data            interface{}
 }

 func (t *executeAsTemplateTransform) Key() internal.ResourceTransformationKey {
@ -61,14 +63,15 @@ func (t *executeAsTemplateTransform) Transform(ctx *resources.ResourceTransforma

 	ctx.OutPath = t.targetPath

-	return templ.Execute(ctx.To, t.data)
+	return t.templateHandler.Execute(templ, ctx.To, t.data)
 }

 func (c *Client) ExecuteAsTemplate(res resources.ResourceTransformer, targetPath string, data interface{}) (resource.Resource, error) {
 	return res.Transform(&executeAsTemplateTransform{
-		rs:           c.rs,
-		targetPath:   helpers.ToSlashTrimLeading(targetPath),
-		textTemplate: c.textTemplate,
-		data:         data,
+		rs:              c.rs,
+		targetPath:      helpers.ToSlashTrimLeading(targetPath),
+		templateHandler: c.templateHandler,
+		textTemplate:    c.textTemplate,
+		data:            data,
 	})
 }
--- a/scripts/fork_go_templates/main.go
+++ b/scripts/fork_go_templates/main.go
@ -57,6 +57,8 @@ var (
 		`"internal/fmtsort"`, `"github.com/gohugoio/hugo/tpl/internal/go_templates/fmtsort"`,
 		// Rename types and function that we want to overload.
 		"type state struct", "type stateOld struct",
+		"func (s *state) evalFunction", "func (s *state) evalFunctionOld",
+		"func (s *state) evalField(", "func (s *state) evalFieldOld(",
 	)

 	htmlTemplateReplacers = strings.NewReplacer(
--- a/tpl/collections/apply.go
+++ b/tpl/collections/apply.go
@ -106,17 +106,8 @@ func applyFnToThis(fn, this reflect.Value, args ...interface{}) (reflect.Value,

 func (ns *Namespace) lookupFunc(fname string) (reflect.Value, bool) {
 	if !strings.ContainsRune(fname, '.') {
-		templ, ok := ns.deps.Tmpl.(tpl.TemplateFuncsGetter)
-		if !ok {
-			panic("Needs a tpl.TemplateFuncsGetter")
-		}
-		fm := templ.GetFuncs()
-		fn, found := fm[fname]
-		if !found {
-			return reflect.Value{}, false
-		}
-
-		return reflect.ValueOf(fn), true
+		templ := ns.deps.Tmpl.(tpl.TemplateFuncGetter)
+		return templ.GetFunc(fname)
 	}

 	ss := strings.SplitN(fname, ".", 2)
--- a/tpl/collections/apply_test.go
+++ b/tpl/collections/apply_test.go
@ -14,6 +14,8 @@
 package collections

 import (
+	"io"
+	"reflect"
 	"testing"

 	"fmt"
@ -33,10 +35,17 @@ func (templateFinder) LookupVariant(name string, variants tpl.TemplateVariants)
 	return nil, false, false
 }

-func (templateFinder) GetFuncs() map[string]interface{} {
-	return map[string]interface{}{
-		"print": fmt.Sprint,
+func (templateFinder) Execute(t tpl.Template, wr io.Writer, data interface{}) error {
+	return nil
+}
+
+func (templateFinder) GetFunc(name string) (reflect.Value, bool) {
+	if name == "dobedobedo" {
+		return reflect.Value{}, false
 	}
+
+	return reflect.ValueOf(fmt.Sprint), true
+
 }

 func TestApply(t *testing.T) {
--- a/tpl/internal/go_templates/texttemplate/exec.go
+++ b/tpl/internal/go_templates/texttemplate/exec.go
@ -558,7 +558,7 @@ func (s *state) evalFieldChain(dot, receiver reflect.Value, node parse.Node, ide
 	return s.evalField(dot, ident[n-1], node, args, final, receiver)
 }

-func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd parse.Node, args []parse.Node, final reflect.Value) reflect.Value {
+func (s *state) evalFunctionOld(dot reflect.Value, node *parse.IdentifierNode, cmd parse.Node, args []parse.Node, final reflect.Value) reflect.Value {
 	s.at(node)
 	name := node.Ident
 	function, ok := findFunction(name, s.tmpl)
@ -571,7 +571,7 @@ func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd
 // evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
 // The 'final' argument represents the return value from the preceding
 // value of the pipeline, if any.
-func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
+func (s *state) evalFieldOld(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
 	if !receiver.IsValid() {
 		if s.tmpl.option.missingKey == mapError { // Treat invalid value as missing map key.
 			s.errorf("nil data; no entry for key %q", fieldName)
--- a/tpl/internal/go_templates/texttemplate/hugo_exec.go
+++ b/tpl/internal/go_templates/texttemplate/hugo_exec.go
@ -1,38 +0,0 @@
-// Copyright 2019 The Hugo Authors. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package template
-
-import (
-	"io"
-
-	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
-)
-
-/*
-
-This files contains the Hugo related addons. All the other files in this
-package is auto generated.
-
-*/
-
-// state represents the state of an execution. It's not part of the
-// template so that multiple executions of the same template
-// can execute in parallel.
-type state struct {
-	tmpl  *Template
-	wr    io.Writer
-	node  parse.Node // current node, for errors
-	vars  []variable // push-down stack of variable values.
-	depth int        // the height of the stack of executing templates.
-}
--- a/tpl/internal/go_templates/texttemplate/hugo_template.go
+++ b/tpl/internal/go_templates/texttemplate/hugo_template.go
@ -27,15 +27,31 @@ package is auto generated.

 */

-// TODO1 name
+// Preparer prepares the template before execution.
 type Preparer interface {
 	Prepare() (*Template, error)
 }

-type TemplateExecutor struct {
+// ExecHelper allows some custom eval hooks.
+type ExecHelper interface {
+	GetFunc(name string) (reflect.Value, bool)
+	GetMapValue(receiver, key reflect.Value) (reflect.Value, bool)
 }

-func (t *TemplateExecutor) Execute(p Preparer, wr io.Writer, data interface{}) error {
+// Executer executes a given template.
+type Executer interface {
+	Execute(p Preparer, wr io.Writer, data interface{}) error
+}
+
+type executer struct {
+	helper ExecHelper
+}
+
+func NewExecuter(helper ExecHelper) Executer {
+	return &executer{helper: helper}
+}
+
+func (t *executer) Execute(p Preparer, wr io.Writer, data interface{}) error {
 	tmpl, err := p.Prepare()
 	if err != nil {
 		return err
@ -47,9 +63,10 @@ func (t *TemplateExecutor) Execute(p Preparer, wr io.Writer, data interface{}) e
 	}

 	state := &state{
-		tmpl: tmpl,
-		wr:   wr,
-		vars: []variable{{"$", value}},
+		helper: t.helper,
+		tmpl:   tmpl,
+		wr:     wr,
+		vars:   []variable{{"$", value}},
 	}

 	return tmpl.executeWithState(state, value)
@ -62,19 +79,6 @@ func (t *Template) Prepare() (*Template, error) {
 	return t, nil
 }

-// Below are modifed structs etc.
-
-// state represents the state of an execution. It's not part of the
-// template so that multiple executions of the same template
-// can execute in parallel.
-type state struct {
-	tmpl  *Template
-	wr    io.Writer
-	node  parse.Node // current node, for errors
-	vars  []variable // push-down stack of variable values.
-	depth int        // the height of the stack of executing templates.
-}
-
 func (t *Template) executeWithState(state *state, value reflect.Value) (err error) {
 	defer errRecover(&err)
 	if t.Tree == nil || t.Root == nil {
@ -83,3 +87,123 @@ func (t *Template) executeWithState(state *state, value reflect.Value) (err erro
 	state.walk(value, t.Root)
 	return
 }
+
+// Below are modifed structs etc.
+
+// state represents the state of an execution. It's not part of the
+// template so that multiple executions of the same template
+// can execute in parallel.
+type state struct {
+	tmpl   *Template
+	helper ExecHelper
+	wr     io.Writer
+	node   parse.Node // current node, for errors
+	vars   []variable // push-down stack of variable values.
+	depth  int        // the height of the stack of executing templates.
+}
+
+func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd parse.Node, args []parse.Node, final reflect.Value) reflect.Value {
+	s.at(node)
+	name := node.Ident
+
+	var function reflect.Value
+	var ok bool
+	if s.helper != nil {
+		function, ok = s.helper.GetFunc(name)
+	}
+
+	if !ok {
+		function, ok = findFunction(name, s.tmpl)
+	}
+
+	if !ok {
+		s.errorf("%q is not a defined function", name)
+	}
+	return s.evalCall(dot, function, cmd, name, args, final)
+}
+
+// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
+// The 'final' argument represents the return value from the preceding
+// value of the pipeline, if any.
+func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
+	if !receiver.IsValid() {
+		if s.tmpl.option.missingKey == mapError { // Treat invalid value as missing map key.
+			s.errorf("nil data; no entry for key %q", fieldName)
+		}
+		return zero
+	}
+	typ := receiver.Type()
+	receiver, isNil := indirect(receiver)
+	if receiver.Kind() == reflect.Interface && isNil {
+		// Calling a method on a nil interface can't work. The
+		// MethodByName method call below would panic.
+		s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
+		return zero
+	}
+
+	// Unless it's an interface, need to get to a value of type *T to guarantee
+	// we see all methods of T and *T.
+	ptr := receiver
+	if ptr.Kind() != reflect.Interface && ptr.Kind() != reflect.Ptr && ptr.CanAddr() {
+		ptr = ptr.Addr()
+	}
+	if method := ptr.MethodByName(fieldName); method.IsValid() {
+		return s.evalCall(dot, method, node, fieldName, args, final)
+	}
+	hasArgs := len(args) > 1 || final != missingVal
+	// It's not a method; must be a field of a struct or an element of a map.
+	switch receiver.Kind() {
+	case reflect.Struct:
+		tField, ok := receiver.Type().FieldByName(fieldName)
+		if ok {
+			field := receiver.FieldByIndex(tField.Index)
+			if tField.PkgPath != "" { // field is unexported
+				s.errorf("%s is an unexported field of struct type %s", fieldName, typ)
+			}
+			// If it's a function, we must call it.
+			if hasArgs {
+				s.errorf("%s has arguments but cannot be invoked as function", fieldName)
+			}
+			return field
+		}
+	case reflect.Map:
+		// If it's a map, attempt to use the field name as a key.
+		nameVal := reflect.ValueOf(fieldName)
+		if nameVal.Type().AssignableTo(receiver.Type().Key()) {
+			if hasArgs {
+				s.errorf("%s is not a method but has arguments", fieldName)
+			}
+			var result reflect.Value
+			if s.helper != nil {
+				result, _ = s.helper.GetMapValue(receiver, nameVal)
+			} else {
+				result = receiver.MapIndex(nameVal)
+			}
+			if !result.IsValid() {
+				switch s.tmpl.option.missingKey {
+				case mapInvalid:
+					// Just use the invalid value.
+				case mapZeroValue:
+					result = reflect.Zero(receiver.Type().Elem())
+				case mapError:
+					s.errorf("map has no entry for key %q", fieldName)
+				}
+			}
+			return result
+		}
+	case reflect.Ptr:
+		etyp := receiver.Type().Elem()
+		if etyp.Kind() == reflect.Struct {
+			if _, ok := etyp.FieldByName(fieldName); !ok {
+				// If there's no such field, say "can't evaluate"
+				// instead of "nil pointer evaluating".
+				break
+			}
+		}
+		if isNil {
+			s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
+		}
+	}
+	s.errorf("can't evaluate field %s in type %s", fieldName, typ)
+	panic("not reached")
+}
--- a/tpl/internal/go_templates/texttemplate/hugo_template_test.go
+++ b/tpl/internal/go_templates/texttemplate/hugo_template_test.go
@ -0,0 +1,71 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package template
+
+import (
+	"bytes"
+	"reflect"
+	"strings"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+type TestStruct struct {
+	S string
+	M map[string]string
+}
+
+type execHelper struct {
+}
+
+func (e *execHelper) GetFunc(name string) (reflect.Value, bool) {
+	if name == "print" {
+		return zero, false
+	}
+	return reflect.ValueOf(func(s string) string {
+		return "hello " + s
+	}), true
+}
+
+func (e *execHelper) GetMapValue(m, key reflect.Value) (reflect.Value, bool) {
+	key = reflect.ValueOf(strings.ToLower(key.String()))
+	return m.MapIndex(key), true
+}
+
+func TestTemplateExecutor(t *testing.T) {
+	c := qt.New(t)
+
+	templ, err := New("").Parse(`
+{{ print "foo" }}
+{{ printf "hugo" }}
+Map: {{ .M.A }}
+
+`)
+
+	c.Assert(err, qt.IsNil)
+
+	ex := NewExecuter(&execHelper{})
+
+	var b bytes.Buffer
+	data := TestStruct{S: "sv", M: map[string]string{"a": "av"}}
+
+	c.Assert(ex.Execute(templ, &b, data), qt.IsNil)
+	got := b.String()
+
+	c.Assert(got, qt.Contains, "foo")
+	c.Assert(got, qt.Contains, "hello hugo")
+	c.Assert(got, qt.Contains, "Map: av")
+
+}
--- a/tpl/partials/partials.go
+++ b/tpl/partials/partials.go
@ -139,7 +139,7 @@ func (ns *Namespace) Include(name string, contextList ...interface{}) (interface
 		w = b
 	}

-	if err := templ.Execute(w, context); err != nil {
+	if err := ns.deps.Tmpl.Execute(templ, w, context); err != nil {
 		return "", err
 	}

--- a/tpl/resources/resources.go
+++ b/tpl/resources/resources.go
@ -53,7 +53,7 @@ func New(deps *deps.Deps) (*Namespace, error) {
 		integrityClient: integrity.New(deps.ResourceSpec),
 		minifyClient:    minifier.New(deps.ResourceSpec),
 		postcssClient:   postcss.New(deps.ResourceSpec),
-		templatesClient: templates.New(deps.ResourceSpec, deps.TextTmpl),
+		templatesClient: templates.New(deps.ResourceSpec, deps.Tmpl, deps.TextTmpl),
 	}, nil
 }

--- a/tpl/template.go
+++ b/tpl/template.go
@ -14,39 +14,22 @@
 package tpl

 import (
-	"fmt"
-	"github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
+	"reflect"

 	"io"
-	"path/filepath"
 	"regexp"
-	"strings"
-	"time"

 	"github.com/gohugoio/hugo/output"

-	"github.com/gohugoio/hugo/common/herrors"
-
-	"github.com/gohugoio/hugo/hugofs"
-
-	"github.com/spf13/afero"
-
 	texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"
-	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
-
-	bp "github.com/gohugoio/hugo/bufferpool"
-	"github.com/gohugoio/hugo/metrics"
-	"github.com/pkg/errors"
 )

-var (
-	_ TemplateExecutor     = (*TemplateAdapter)(nil)
-	_ TemplateInfoProvider = (*TemplateAdapter)(nil)
-)
+var _ TemplateInfoProvider = (*TemplateInfo)(nil)

-// TemplateHandler manages the collection of templates.
-type TemplateHandler interface {
-	TemplateFinder
+// TemplateManager manages the collection of templates.
+type TemplateManager interface {
+	TemplateHandler
+	TemplateFuncGetter
 	AddTemplate(name, tpl string) error
 	AddLateTemplate(name, tpl string) error
 	LoadTemplates(prefix string) error
@ -68,6 +51,12 @@ type TemplateFinder interface {
 	TemplateLookupVariant
 }

+// TemplateHandler finds and executes templates.
+type TemplateHandler interface {
+	TemplateFinder
+	Execute(t Template, wr io.Writer, data interface{}) error
+}
+
 type TemplateLookup interface {
 	Lookup(name string) (Template, bool)
 }
@ -87,8 +76,8 @@ type TemplateLookupVariant interface {

 // Template is the common interface between text/template and html/template.
 type Template interface {
-	Execute(wr io.Writer, data interface{}) error
 	Name() string
+	Prepare() (*texttemplate.Template, error)
 }

 // TemplateInfoProvider provides some contextual information about a template.
@ -107,30 +96,15 @@ type TemplateParseFinder interface {
 	TemplateFinder
 }

-// TemplateExecutor adds some extras to Template.
-type TemplateExecutor interface {
-	Template
-	ExecuteToString(data interface{}) (string, error)
-	Tree() string
-}
-
 // TemplateDebugger prints some debug info to stdoud.
 type TemplateDebugger interface {
 	Debug()
 }

-// TemplateAdapter implements the TemplateExecutor interface.
-type TemplateAdapter struct {
+// TemplateInfo wraps a Template with some additional information.
+type TemplateInfo struct {
 	Template
-	Metrics metrics.Provider
-
 	Info Info
-
-	// The filesystem where the templates are stored.
-	Fs afero.Fs
-
-	// Maps to base template if relevant.
-	NameBaseTemplateName map[string]string
 }

 var baseOfRe = regexp.MustCompile("template: (.*?):")
@ -143,165 +117,11 @@ func extractBaseOf(err string) string {
 	return ""
 }

-// Execute executes the current template. The actual execution is performed
-// by the embedded text or html template, but we add an implementation here so
-// we can add a timer for some metrics.
-func (t *TemplateAdapter) Execute(w io.Writer, data interface{}) (execErr error) {
-	defer func() {
-		// Panics in templates are a little bit too common (nil pointers etc.)
-		// See https://github.com/gohugoio/hugo/issues/5327
-		if r := recover(); r != nil {
-			execErr = t.addFileContext(t.Name(), fmt.Errorf(`panic in Execute: %s. See "https://github.com/gohugoio/hugo/issues/5327" for the reason why we cannot provide a better error message for this`, r))
-		}
-	}()
-
-	if t.Metrics != nil {
-		defer t.Metrics.MeasureSince(t.Name(), time.Now())
-	}
-
-	execErr = t.Template.Execute(w, data)
-	if execErr != nil {
-		execErr = t.addFileContext(t.Name(), execErr)
-	}
-
-	return
-}
-
-func (t *TemplateAdapter) TemplateInfo() Info {
+func (t *TemplateInfo) TemplateInfo() Info {
 	return t.Info
 }

-// The identifiers may be truncated in the log, e.g.
-// "executing "main" at <$scaled.SRelPermalin...>: can't evaluate field SRelPermalink in type *resource.Image"
-var identifiersRe = regexp.MustCompile(`at \<(.*?)(\.{3})?\>:`)
-
-func (t *TemplateAdapter) extractIdentifiers(line string) []string {
-	m := identifiersRe.FindAllStringSubmatch(line, -1)
-	identifiers := make([]string, len(m))
-	for i := 0; i < len(m); i++ {
-		identifiers[i] = m[i][1]
-	}
-	return identifiers
-}
-
-func (t *TemplateAdapter) addFileContext(name string, inerr error) error {
-	if strings.HasPrefix(t.Name(), "_internal") {
-		return inerr
-	}
-
-	f, realFilename, err := t.fileAndFilename(t.Name())
-	if err != nil {
-		return inerr
-
-	}
-	defer f.Close()
-
-	master, hasMaster := t.NameBaseTemplateName[name]
-
-	ferr := errors.Wrap(inerr, "execute of template failed")
-
-	// Since this can be a composite of multiple template files (single.html + baseof.html etc.)
-	// we potentially need to look in both -- and cannot rely on line number alone.
-	lineMatcher := func(m herrors.LineMatcher) bool {
-		if m.Position.LineNumber != m.LineNumber {
-			return false
-		}
-		if !hasMaster {
-			return true
-		}
-
-		identifiers := t.extractIdentifiers(m.Error.Error())
-
-		for _, id := range identifiers {
-			if strings.Contains(m.Line, id) {
-				return true
-			}
-		}
-		return false
-	}
-
-	fe, ok := herrors.WithFileContext(ferr, realFilename, f, lineMatcher)
-	if ok || !hasMaster {
-		return fe
-	}
-
-	// Try the base template if relevant
-	f, realFilename, err = t.fileAndFilename(master)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
-	fe, ok = herrors.WithFileContext(ferr, realFilename, f, lineMatcher)
-
-	if !ok {
-		// Return the most specific.
-		return ferr
-
-	}
-	return fe
-
-}
-
-func (t *TemplateAdapter) fileAndFilename(name string) (afero.File, string, error) {
-	fs := t.Fs
-	filename := filepath.FromSlash(name)
-
-	fi, err := fs.Stat(filename)
-	if err != nil {
-		return nil, "", err
-	}
-	fim := fi.(hugofs.FileMetaInfo)
-	meta := fim.Meta()
-
-	f, err := meta.Open()
-	if err != nil {
-		return nil, "", errors.Wrapf(err, "failed to open template file %q:", filename)
-	}
-
-	return f, meta.Filename(), nil
-}
-
-// ExecuteToString executes the current template and returns the result as a
-// string.
-func (t *TemplateAdapter) ExecuteToString(data interface{}) (string, error) {
-	b := bp.GetBuffer()
-	defer bp.PutBuffer(b)
-	if err := t.Execute(b, data); err != nil {
-		return "", err
-	}
-	return b.String(), nil
-}
-
-// Tree returns the template Parse tree as a string.
-// Note: this isn't safe for parallel execution on the same template
-// vs Lookup and Execute.
-func (t *TemplateAdapter) Tree() string {
-	var tree *parse.Tree
-	switch tt := t.Template.(type) {
-	case *template.Template:
-		tree = tt.Tree
-	case *texttemplate.Template:
-		tree = tt.Tree
-	default:
-		panic("Unknown template")
-	}
-
-	if tree == nil || tree.Root == nil {
-		return ""
-	}
-	s := tree.Root.String()
-
-	return s
-}
-
-// TemplateFuncsGetter allows to get a map of functions.
-type TemplateFuncsGetter interface {
-	GetFuncs() map[string]interface{}
-}
-
-// TemplateTestMocker adds a way to override some template funcs during tests.
-// The interface is named so it's not used in regular application code.
-type TemplateTestMocker interface {
-	SetFuncs(funcMap map[string]interface{})
+// TemplateFuncGetter allows to find a template func by name.
+type TemplateFuncGetter interface {
+	GetFunc(name string) (reflect.Value, bool)
 }
--- a/tpl/tplimpl/embedded/templates.autogen.go
+++ b/tpl/tplimpl/embedded/templates.autogen.go
@ -87,6 +87,7 @@ var EmbeddedTemplates = [][2]string{
 	{{ end }}
 </sitemapindex>
 `},
+	{`alias.html`, `<!DOCTYPE html><html><head><title>{{ .Permalink }}</title><link rel="canonical" href="{{ .Permalink }}"/><meta name="robots" content="noindex"><meta charset="utf-8" /><meta http-equiv="refresh" content="0; url={{ .Permalink }}" /></head></html>`},
 	{`disqus.html`, `{{- $pc := .Site.Config.Privacy.Disqus -}}
 {{- if not $pc.Disable -}}
 {{ if .Site.DisqusShortname }}<div id="disqus_thread"></div>
--- a/tpl/tplimpl/embedded/templates/alias.html
+++ b/tpl/tplimpl/embedded/templates/alias.html
@ -0,0 +1 @@
+<!DOCTYPE html><html><head><title>{{ .Permalink }}</title><link rel="canonical" href="{{ .Permalink }}"/><meta name="robots" content="noindex"><meta charset="utf-8" /><meta http-equiv="refresh" content="0; url={{ .Permalink }}" /></head></html>
--- a/tpl/tplimpl/shortcodes.go
+++ b/tpl/tplimpl/shortcodes.go
@ -61,11 +61,6 @@ func (s *shortcodeTemplates) fromVariants(variants tpl.TemplateVariants) (shortc
 	})
 }

-// Get the most specific template given a full name, e.g  gtag.no.amp.html.
-func (s *shortcodeTemplates) fromName(name string) (shortcodeVariant, bool) {
-	return s.fromVariantsSlice(templateVariants(name))
-}
-
 func (s *shortcodeTemplates) fromVariantsSlice(variants []string) (shortcodeVariant, bool) {
 	var (
 		bestMatch       shortcodeVariant
--- a/tpl/tplimpl/template.go
+++ b/tpl/tplimpl/template.go
--- a/tpl/tplimpl/templateFuncster.go
+++ b/tpl/tplimpl/templateFuncster.go
@ -12,22 +12,3 @@
 // limitations under the License.

 package tplimpl
-
-import (
-	"html/template"
-
-	"github.com/gohugoio/hugo/deps"
-)
-
-// Some of the template funcs are'nt entirely stateless.
-type templateFuncster struct {
-	funcMap template.FuncMap
-
-	*deps.Deps
-}
-
-func newTemplateFuncster(deps *deps.Deps) *templateFuncster {
-	return &templateFuncster{
-		Deps: deps,
-	}
-}
--- a/tpl/tplimpl/templateProvider.go
+++ b/tpl/tplimpl/templateProvider.go
@ -29,8 +29,8 @@ func (*TemplateProvider) Update(deps *deps.Deps) error {
 	newTmpl := newTemplateAdapter(deps)
 	deps.Tmpl = newTmpl
 	deps.TextTmpl = newTmpl.wrapTextTemplate(newTmpl.text.standalone)
-
-	newTmpl.initFuncs()
+	// These needs to be there at parse time.
+	newTmpl.initTemplateExecuter()

 	if err := newTmpl.loadEmbedded(); err != nil {
 		return err
--- a/tpl/tplimpl/template_ast_transformers.go
+++ b/tpl/tplimpl/template_ast_transformers.go
@ -14,9 +14,7 @@
 package tplimpl

 import (
-	"github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
-
-	"strings"
+	template "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"

 	texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"
 	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
@ -27,19 +25,6 @@ import (
 	"github.com/pkg/errors"
 )

-// decl keeps track of the variable mappings, i.e. $mysite => .Site etc.
-type decl map[string]string
-
-const (
-	paramsIdentifier = "Params"
-)
-
-// Containers that may contain Params that we will not touch.
-var reservedContainers = map[string]bool{
-	// Aka .Site.Data.Params which must stay case sensitive.
-	"Data": true,
-}
-
 type templateType int

 const (
@ -49,7 +34,6 @@ const (
 )

 type templateContext struct {
-	decl     decl
 	visited  map[string]bool
 	notFound map[string]bool
 	lookupFn func(name string) *parse.Tree
@ -89,7 +73,6 @@ func newTemplateContext(lookupFn func(name string) *parse.Tree) *templateContext
 	return &templateContext{
 		Info:     tpl.Info{Config: tpl.DefaultConfig},
 		lookupFn: lookupFn,
-		decl:     make(map[string]string),
 		visited:  make(map[string]bool),
 		notFound: make(map[string]bool)}
 }
@ -219,11 +202,6 @@ func (c *templateContext) applyTransformations(n parse.Node) (bool, error) {
 		}
 	case *parse.PipeNode:
 		c.collectConfig(x)
-		if len(x.Decl) == 1 && len(x.Cmds) == 1 {
-			// maps $site => .Site etc.
-			c.decl[x.Decl[0].Ident[0]] = x.Cmds[0].String()
-		}
-
 		for i, cmd := range x.Cmds {
 			keep, _ := c.applyTransformations(cmd)
 			if !keep {
@ -237,17 +215,8 @@ func (c *templateContext) applyTransformations(n parse.Node) (bool, error) {

 		for _, elem := range x.Args {
 			switch an := elem.(type) {
-			case *parse.FieldNode:
-				c.updateIdentsIfNeeded(an.Ident)
-			case *parse.VariableNode:
-				c.updateIdentsIfNeeded(an.Ident)
 			case *parse.PipeNode:
 				c.applyTransformations(an)
-			case *parse.ChainNode:
-				// site.Params...
-				if len(an.Field) > 1 && an.Field[0] == paramsIdentifier {
-					c.updateIdentsIfNeeded(an.Field)
-				}
 			}
 		}
 		return keep, c.err
@ -262,19 +231,6 @@ func (c *templateContext) applyTransformationsToNodes(nodes ...parse.Node) {
 	}
 }

-func (c *templateContext) updateIdentsIfNeeded(idents []string) {
-	index := c.decl.indexOfReplacementStart(idents)
-
-	if index == -1 {
-		return
-	}
-
-	for i := index; i < len(idents); i++ {
-		idents[i] = strings.ToLower(idents[i])
-	}
-
-}
-
 func (c *templateContext) hasIdent(idents []string, ident string) bool {
 	for _, id := range idents {
 		if id == ident {
@ -376,160 +332,3 @@ func (c *templateContext) collectReturnNode(n *parse.CommandNode) bool {
 	return false

 }
-
-// indexOfReplacementStart will return the index of where to start doing replacement,
-// -1 if none needed.
-func (d decl) indexOfReplacementStart(idents []string) int {
-
-	l := len(idents)
-
-	if l == 0 {
-		return -1
-	}
-
-	if l == 1 {
-		first := idents[0]
-		if first == "" || first == paramsIdentifier || first[0] == '$' {
-			// This can not be a Params.x
-			return -1
-		}
-	}
-
-	var lookFurther bool
-	var needsVarExpansion bool
-	for _, ident := range idents {
-		if ident[0] == '$' {
-			lookFurther = true
-			needsVarExpansion = true
-			break
-		} else if ident == paramsIdentifier {
-			lookFurther = true
-			break
-		}
-	}
-
-	if !lookFurther {
-		return -1
-	}
-
-	var resolvedIdents []string
-
-	if !needsVarExpansion {
-		resolvedIdents = idents
-	} else {
-		var ok bool
-		resolvedIdents, ok = d.resolveVariables(idents)
-		if !ok {
-			return -1
-		}
-	}
-
-	var paramFound bool
-	for i, ident := range resolvedIdents {
-		if ident == paramsIdentifier {
-			if i > 0 {
-				container := resolvedIdents[i-1]
-				if reservedContainers[container] {
-					// .Data.Params.someKey
-					return -1
-				}
-			}
-
-			paramFound = true
-			break
-		}
-	}
-
-	if !paramFound {
-		return -1
-	}
-
-	var paramSeen bool
-	idx := -1
-	for i, ident := range idents {
-		if ident == "" || ident[0] == '$' {
-			continue
-		}
-
-		if ident == paramsIdentifier {
-			paramSeen = true
-			idx = -1
-
-		} else {
-			if paramSeen {
-				return i
-			}
-			if idx == -1 {
-				idx = i
-			}
-		}
-	}
-	return idx
-
-}
-
-func (d decl) resolveVariables(idents []string) ([]string, bool) {
-	var (
-		replacements []string
-		replaced     []string
-	)
-
-	// An Ident can start out as one of
-	// [Params] [$blue] [$colors.Blue]
-	// We need to resolve the variables, so
-	// $blue => [Params Colors Blue]
-	// etc.
-	replacements = []string{idents[0]}
-
-	// Loop until there are no more $vars to resolve.
-	for i := 0; i < len(replacements); i++ {
-
-		if i > 20 {
-			// bail out
-			return nil, false
-		}
-
-		potentialVar := replacements[i]
-
-		if potentialVar == "$" {
-			continue
-		}
-
-		if potentialVar == "" || potentialVar[0] != '$' {
-			// leave it as is
-			replaced = append(replaced, strings.Split(potentialVar, ".")...)
-			continue
-		}
-
-		replacement, ok := d[potentialVar]
-
-		if !ok {
-			// Temporary range vars. We do not care about those.
-			return nil, false
-		}
-
-		if !d.isKeyword(replacement) {
-			continue
-		}
-
-		replacement = strings.TrimPrefix(replacement, ".")
-
-		if replacement == "" {
-			continue
-		}
-
-		if replacement[0] == '$' {
-			// Needs further expansion
-			replacements = append(replacements, strings.Split(replacement, ".")...)
-		} else {
-			replaced = append(replaced, strings.Split(replacement, ".")...)
-		}
-	}
-
-	return append(replaced, idents[1:]...), true
-
-}
-
-func (d decl) isKeyword(s string) bool {
-	return !strings.ContainsAny(s, " -\"")
-}
--- a/tpl/tplimpl/template_ast_transformers_test.go
+++ b/tpl/tplimpl/template_ast_transformers_test.go
@ -13,400 +13,18 @@
 package tplimpl

 import (
-	"bytes"
-	"fmt"
-	"github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
+	"strings"
+
+	template "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"

 	"testing"
 	"time"

 	"github.com/gohugoio/hugo/tpl"

-	"github.com/spf13/cast"
-
 	qt "github.com/frankban/quicktest"
 )

-type paramsHolder struct {
-	params map[string]interface{}
-	page   *paramsHolder
-}
-
-func (p paramsHolder) Params() map[string]interface{} {
-	return p.params
-}
-
-func (p paramsHolder) GetPage(arg string) *paramsHolder {
-	return p.page
-}
-
-var (
-	testFuncs = map[string]interface{}{
-		"getif":  func(v interface{}) interface{} { return v },
-		"ToTime": func(v interface{}) interface{} { return cast.ToTime(v) },
-		"First":  func(v ...interface{}) interface{} { return v[0] },
-		"Echo":   func(v interface{}) interface{} { return v },
-		"where": func(seq, key interface{}, args ...interface{}) (interface{}, error) {
-			return map[string]interface{}{
-				"ByWeight": fmt.Sprintf("%v:%v:%v", seq, key, args),
-			}, nil
-		},
-		"site": func() paramsHolder {
-			return paramsHolder{
-				params: map[string]interface{}{
-					"lower": "global-site",
-				},
-				page: &paramsHolder{
-					params: map[string]interface{}{
-						"lower": "page",
-					},
-				},
-			}
-		},
-	}
-
-	paramsData = map[string]interface{}{
-
-		"NotParam": "Hi There",
-		"Slice":    []int{1, 3},
-		"Params": map[string]interface{}{
-			"lower":  "P1L",
-			"slice":  []int{1, 3},
-			"mydate": "1972-01-28",
-		},
-		"Pages": map[string]interface{}{
-			"ByWeight": []int{1, 3},
-		},
-		"CurrentSection": map[string]interface{}{
-			"Params": map[string]interface{}{
-				"lower": "pcurrentsection",
-			},
-		},
-		"Site": map[string]interface{}{
-			"Params": map[string]interface{}{
-				"lower": "P2L",
-				"slice": []int{1, 3},
-			},
-			"Language": map[string]interface{}{
-				"Params": map[string]interface{}{
-					"lower": "P22L",
-					"nested": map[string]interface{}{
-						"lower": "P22L_nested",
-					},
-				},
-			},
-			"Data": map[string]interface{}{
-				"Params": map[string]interface{}{
-					"NOLOW": "P3H",
-				},
-			},
-		},
-		"Site2": paramsHolder{
-			params: map[string]interface{}{
-				"lower": "global-site",
-			},
-			page: &paramsHolder{
-				params: map[string]interface{}{
-					"lower": "page",
-				},
-			},
-		},
-	}
-
-	paramsTempl = `
-{{ $page := . }}
-{{ $pages := .Pages }}
-{{ $pageParams := .Params }}
-{{ $site := .Site }}
-{{ $siteParams := .Site.Params }}
-{{ $data := .Site.Data }}
-{{ $notparam := .NotParam }}
-
-PCurrentSection: {{ .CurrentSection.Params.LOWER }}
-P1: {{ .Params.LOWER }}
-P1_2: {{ $.Params.LOWER }}
-P1_3: {{ $page.Params.LOWER }}
-P1_4: {{ $pageParams.LOWER }}
-P2: {{ .Site.Params.LOWER }}
-P2_2: {{ $.Site.Params.LOWER }}
-P2_3: {{ $site.Params.LOWER }}
-P2_4: {{ $siteParams.LOWER }}
-P22: {{ .Site.Language.Params.LOWER }}
-P22_nested: {{ .Site.Language.Params.NESTED.LOWER }}
-P3: {{ .Site.Data.Params.NOLOW }}
-P3_2: {{ $.Site.Data.Params.NOLOW }}
-P3_3: {{ $site.Data.Params.NOLOW }}
-P3_4: {{ $data.Params.NOLOW }}
-P4: {{ range $i, $e := .Site.Params.SLICE }}{{ $e }}{{ end }}
-P5: {{ Echo .Params.LOWER }}
-P5_2: {{ Echo $site.Params.LOWER }}
-{{ if .Params.LOWER }}
-IF: {{ .Params.LOWER }}
-{{ end }}
-{{ if .Params.NOT_EXIST }}
-{{ else }}
-ELSE: {{ .Params.LOWER }}
-{{ end }}
-
-
-{{ with .Params.LOWER }}
-WITH: {{ . }}
-{{ end }}
-
-
-{{ range .Slice }}
-RANGE: {{ . }}: {{ $.Params.LOWER }}
-{{ end }}
-{{ index .Slice 1 }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ .NotParam }}
-{{ $notparam }}
-
-
-{{ $lower := .Site.Params.LOWER }}
-F1: {{ printf "themes/%s-theme" .Site.Params.LOWER }}
-F2: {{ Echo (printf "themes/%s-theme" $lower) }}
-F3: {{ Echo (printf "themes/%s-theme" .Site.Params.LOWER) }}
-
-PSLICE: {{ range .Params.SLICE }}PSLICE{{.}}|{{ end }}
-
-{{ $pages := "foo" }}
-{{ $pages := where $pages ".Params.toc_hide" "!=" true }}
-PARAMS STRING: {{ $pages.ByWeight }}
-PARAMS STRING2: {{ with $pages }}{{ .ByWeight }}{{ end }}
-{{ $pages3 := where ".Params.TOC_HIDE" "!=" .Params.LOWER }}
-PARAMS STRING3: {{ $pages3.ByWeight }}
-{{ $first := First .Pages .Site.Params.LOWER }}
-PARAMS COMPOSITE: {{ $first.ByWeight }}
-
-
-{{ $time := $.Params.MyDate | ToTime }}
-{{ $time = $time.AddDate 0 1 0 }}
-PARAMS TIME: {{ $time.Format "2006-01-02" }}
-
-{{ $_x :=  $.Params.MyDate | ToTime }}
-PARAMS TIME2: {{ $_x.AddDate 0 1 0 }}
-
-PARAMS SITE GLOBAL1: {{ site.Params.LOwER }}
-{{ $lower := site.Params.LOwER }}
-{{ $site := site }}
-PARAMS SITE GLOBAL2: {{ $lower }}
-PARAMS SITE GLOBAL3: {{ $site.Params.LOWER }}
-
-{{ $p := $site.GetPage "foo" }}
-PARAMS GETPAGE: {{ $p.Params.LOWER }}
-{{ $p := .Site2.GetPage "foo" }}
-PARAMS GETPAGE2: {{ $p.Params.LOWER }}
-`
-)
-
-func TestParamsKeysToLower(t *testing.T) {
-	t.Parallel()
-	c := qt.New(t)
-
-	_, err := applyTemplateTransformers(templateUndefined, nil, nil)
-	c.Assert(err, qt.Not(qt.IsNil))
-
-	templ, err := template.New("foo").Funcs(testFuncs).Parse(paramsTempl)
-
-	c.Assert(err, qt.IsNil)
-
-	ctx := newTemplateContext(createParseTreeLookup(templ))
-
-	c.Assert(ctx.decl.indexOfReplacementStart([]string{}), qt.Equals, -1)
-
-	ctx.applyTransformations(templ.Tree.Root)
-
-	var b bytes.Buffer
-
-	c.Assert(templ.Execute(&b, paramsData), qt.IsNil)
-
-	result := b.String()
-
-	c.Assert(result, qt.Contains, "P1: P1L")
-	c.Assert(result, qt.Contains, "P1_2: P1L")
-	c.Assert(result, qt.Contains, "P1_3: P1L")
-	c.Assert(result, qt.Contains, "P1_4: P1L")
-	c.Assert(result, qt.Contains, "P2: P2L")
-	c.Assert(result, qt.Contains, "P2_2: P2L")
-	c.Assert(result, qt.Contains, "P2_3: P2L")
-	c.Assert(result, qt.Contains, "P2_4: P2L")
-	c.Assert(result, qt.Contains, "P22: P22L")
-	c.Assert(result, qt.Contains, "P22_nested: P22L_nested")
-	c.Assert(result, qt.Contains, "P3: P3H")
-	c.Assert(result, qt.Contains, "P3_2: P3H")
-	c.Assert(result, qt.Contains, "P3_3: P3H")
-	c.Assert(result, qt.Contains, "P3_4: P3H")
-	c.Assert(result, qt.Contains, "P4: 13")
-	c.Assert(result, qt.Contains, "P5: P1L")
-	c.Assert(result, qt.Contains, "P5_2: P2L")
-
-	c.Assert(result, qt.Contains, "IF: P1L")
-	c.Assert(result, qt.Contains, "ELSE: P1L")
-
-	c.Assert(result, qt.Contains, "WITH: P1L")
-
-	c.Assert(result, qt.Contains, "RANGE: 3: P1L")
-
-	c.Assert(result, qt.Contains, "Hi There")
-
-	// Issue #2740
-	c.Assert(result, qt.Contains, "F1: themes/P2L-theme")
-	c.Assert(result, qt.Contains, "F2: themes/P2L-theme")
-	c.Assert(result, qt.Contains, "F3: themes/P2L-theme")
-
-	c.Assert(result, qt.Contains, "PSLICE: PSLICE1|PSLICE3|")
-	c.Assert(result, qt.Contains, "PARAMS STRING: foo:.Params.toc_hide:[!= true]")
-	c.Assert(result, qt.Contains, "PARAMS STRING2: foo:.Params.toc_hide:[!= true]")
-	c.Assert(result, qt.Contains, "PARAMS STRING3: .Params.TOC_HIDE:!=:[P1L]")
-
-	// Issue #5094
-	c.Assert(result, qt.Contains, "PARAMS COMPOSITE: [1 3]")
-
-	// Issue #5068
-	c.Assert(result, qt.Contains, "PCurrentSection: pcurrentsection")
-
-	// Issue #5541
-	c.Assert(result, qt.Contains, "PARAMS TIME: 1972-02-28")
-	c.Assert(result, qt.Contains, "PARAMS TIME2: 1972-02-28")
-
-	// Issue ##5615
-	c.Assert(result, qt.Contains, "PARAMS SITE GLOBAL1: global-site")
-	c.Assert(result, qt.Contains, "PARAMS SITE GLOBAL2: global-site")
-	c.Assert(result, qt.Contains, "PARAMS SITE GLOBAL3: global-site")
-
-	//
-	c.Assert(result, qt.Contains, "PARAMS GETPAGE: page")
-	c.Assert(result, qt.Contains, "PARAMS GETPAGE2: page")
-
-}
-
-func BenchmarkTemplateParamsKeysToLower(b *testing.B) {
-	templ, err := template.New("foo").Funcs(testFuncs).Parse(paramsTempl)
-
-	if err != nil {
-		b.Fatal(err)
-	}
-
-	templates := make([]*template.Template, b.N)
-
-	for i := 0; i < b.N; i++ {
-		templates[i], err = templ.Clone()
-		if err != nil {
-			b.Fatal(err)
-		}
-	}
-
-	b.ResetTimer()
-
-	for i := 0; i < b.N; i++ {
-		c := newTemplateContext(createParseTreeLookup(templates[i]))
-		c.applyTransformations(templ.Tree.Root)
-	}
-}
-
-func TestParamsKeysToLowerVars(t *testing.T) {
-	t.Parallel()
-	c := qt.New(t)
-
-	var (
-		data = map[string]interface{}{
-			"Params": map[string]interface{}{
-				"colors": map[string]interface{}{
-					"blue": "Amber",
-					"pretty": map[string]interface{}{
-						"first": "Indigo",
-					},
-				},
-			},
-		}
-
-		// This is how Amber behaves:
-		paramsTempl = `
-{{$__amber_1 := .Params.Colors}}
-{{$__amber_2 := $__amber_1.Blue}}
-{{$__amber_3 := $__amber_1.Pretty}}
-{{$__amber_4 := .Params}}
-
-Color: {{$__amber_2}}
-Blue: {{ $__amber_1.Blue}}
-Pretty First1: {{ $__amber_3.First}}
-Pretty First2: {{ $__amber_1.Pretty.First}}
-Pretty First3: {{ $__amber_4.COLORS.PRETTY.FIRST}}
-`
-	)
-
-	templ, err := template.New("foo").Parse(paramsTempl)
-
-	c.Assert(err, qt.IsNil)
-
-	ctx := newTemplateContext(createParseTreeLookup(templ))
-
-	ctx.applyTransformations(templ.Tree.Root)
-
-	var b bytes.Buffer
-
-	c.Assert(templ.Execute(&b, data), qt.IsNil)
-
-	result := b.String()
-
-	c.Assert(result, qt.Contains, "Color: Amber")
-	c.Assert(result, qt.Contains, "Blue: Amber")
-	c.Assert(result, qt.Contains, "Pretty First1: Indigo")
-	c.Assert(result, qt.Contains, "Pretty First2: Indigo")
-	c.Assert(result, qt.Contains, "Pretty First3: Indigo")
-
-}
-
-func TestParamsKeysToLowerInBlockTemplate(t *testing.T) {
-	t.Parallel()
-	c := qt.New(t)
-
-	var (
-		data = map[string]interface{}{
-			"Params": map[string]interface{}{
-				"lower": "P1L",
-			},
-		}
-
-		master = `
-P1: {{ .Params.LOWER }}
-{{ block "main" . }}DEFAULT{{ end }}`
-		overlay = `
-{{ define "main" }}
-P2: {{ .Params.LOWER }}
-{{ end }}`
-	)
-
-	masterTpl, err := template.New("foo").Parse(master)
-	c.Assert(err, qt.IsNil)
-
-	overlayTpl, err := template.Must(masterTpl.Clone()).Parse(overlay)
-	c.Assert(err, qt.IsNil)
-	overlayTpl = overlayTpl.Lookup(overlayTpl.Name())
-
-	ctx := newTemplateContext(createParseTreeLookup(overlayTpl))
-
-	ctx.applyTransformations(overlayTpl.Tree.Root)
-
-	var b bytes.Buffer
-
-	c.Assert(overlayTpl.Execute(&b, data), qt.IsNil)
-
-	result := b.String()
-
-	c.Assert(result, qt.Contains, "P1: P1L")
-	c.Assert(result, qt.Contains, "P2: P1L")
-}
-
 // Issue #2927
 func TestTransformRecursiveTemplate(t *testing.T) {
 	c := qt.New(t)
@ -479,7 +97,7 @@ func TestInsertIsZeroFunc(t *testing.T) {
 	)

 	d := newD(c)
-	h := d.Tmpl.(tpl.TemplateHandler)
+	h := d.Tmpl.(tpl.TemplateManager)

 	// HTML templates
 	c.Assert(h.AddTemplate("mytemplate.html", templ1), qt.IsNil)
@ -493,9 +111,13 @@ func TestInsertIsZeroFunc(t *testing.T) {

 	for _, name := range []string{"mytemplate.html", "mytexttemplate.txt"} {
 		tt, _ := d.Tmpl.Lookup(name)
-		result, err := tt.(tpl.TemplateExecutor).ExecuteToString(ctx)
+		sb := &strings.Builder{}
+
+		err := d.Tmpl.Execute(tt, sb, ctx)
 		c.Assert(err, qt.IsNil)

+		result := sb.String()
+
 		c.Assert(result, qt.Contains, ".True: TRUE")
 		c.Assert(result, qt.Contains, ".TimeZero1: FALSE")
 		c.Assert(result, qt.Contains, ".TimeZero2: FALSE")
--- a/tpl/tplimpl/template_funcs.go
+++ b/tpl/tplimpl/template_funcs.go
@ -16,7 +16,13 @@
 package tplimpl

 import (
-	"html/template"
+	"reflect"
+	"strings"
+
+	"github.com/gohugoio/hugo/common/maps"
+
+	template "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
+	texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"

 	"github.com/gohugoio/hugo/deps"

@ -49,7 +55,55 @@ import (
 	_ "github.com/gohugoio/hugo/tpl/urls"
 )

+var _ texttemplate.ExecHelper = (*templateExecHelper)(nil)
+var zero reflect.Value
+
+type templateExecHelper struct {
+	funcs map[string]reflect.Value
+}
+
+func (t *templateExecHelper) GetFunc(name string) (reflect.Value, bool) {
+	if fn, found := t.funcs[name]; found {
+		return fn, true
+	}
+	return zero, false
+}
+
+func (t *templateExecHelper) GetMapValue(receiver, key reflect.Value) (reflect.Value, bool) {
+	if params, ok := receiver.Interface().(maps.Params); ok {
+		// Case insensitive.
+		keystr := strings.ToLower(key.String())
+		v, found := params[keystr]
+		if !found {
+			return zero, false
+		}
+		return reflect.ValueOf(v), true
+	}
+
+	v := receiver.MapIndex(key)
+
+	return v, v.IsValid()
+}
+
+func newTemplateExecuter(d *deps.Deps) (texttemplate.Executer, map[string]reflect.Value) {
+	funcs := createFuncMap(d)
+	funcsv := make(map[string]reflect.Value)
+
+	for k, v := range funcs {
+		funcsv[k] = reflect.ValueOf(v)
+	}
+
+	exeHelper := &templateExecHelper{
+		funcs: funcsv,
+	}
+
+	return texttemplate.NewExecuter(
+		exeHelper,
+	), funcsv
+}
+
 func createFuncMap(d *deps.Deps) map[string]interface{} {
+
 	funcMap := template.FuncMap{}

 	// Merge the namespace funcs
@ -71,10 +125,12 @@ func createFuncMap(d *deps.Deps) map[string]interface{} {

 	}

+	if d.OverloadedTemplateFuncs != nil {
+		for k, v := range d.OverloadedTemplateFuncs {
+			funcMap[k] = v
+		}
+	}
+
 	return funcMap

 }
-func (t *templateFuncster) initFuncMap(funcMap template.FuncMap) {
-	t.funcMap = funcMap
-	t.Tmpl.(*templateHandler).setFuncs(funcMap)
-}
--- a/tpl/tplimpl/template_funcs_test.go
+++ b/tpl/tplimpl/template_funcs_test.go
@ -119,7 +119,7 @@ func TestTemplateFuncsExamples(t *testing.T) {
 		for _, mm := range ns.MethodMappings {
 			for i, example := range mm.Examples {
 				in, expected := example[0], example[1]
-				d.WithTemplate = func(templ tpl.TemplateHandler) error {
+				d.WithTemplate = func(templ tpl.TemplateManager) error {
 					c.Assert(templ.AddTemplate("test", in), qt.IsNil)
 					c.Assert(templ.AddTemplate("partials/header.html", "<title>Hugo Rocks!</title>"), qt.IsNil)
 					return nil
@ -128,7 +128,7 @@ func TestTemplateFuncsExamples(t *testing.T) {

 				var b bytes.Buffer
 				templ, _ := d.Tmpl.Lookup("test")
-				c.Assert(templ.Execute(&b, &data), qt.IsNil)
+				c.Assert(d.Tmpl.Execute(templ, &b, &data), qt.IsNil)
 				if b.String() != expected {
 					t.Fatalf("%s[%d]: got %q expected %q", ns.Name, i, b.String(), expected)
 				}
@ -154,7 +154,7 @@ func TestPartialCached(t *testing.T) {

 	config := newDepsConfig(v)

-	config.WithTemplate = func(templ tpl.TemplateHandler) error {
+	config.WithTemplate = func(templ tpl.TemplateManager) error {
 		err := templ.AddTemplate("partials/"+name, partial)
 		if err != nil {
 			return err
@ -208,7 +208,7 @@ func BenchmarkPartialCached(b *testing.B) {
 func doBenchmarkPartial(b *testing.B, f func(ns *partials.Namespace) error) {
 	c := qt.New(b)
 	config := newDepsConfig(viper.New())
-	config.WithTemplate = func(templ tpl.TemplateHandler) error {
+	config.WithTemplate = func(templ tpl.TemplateManager) error {
 		err := templ.AddTemplate("partials/bench1", `{{ shuffle (seq 1 10) }}`)
 		if err != nil {
 			return err
--- a/tpl/tplimpl/template_info_test.go
+++ b/tpl/tplimpl/template_info_test.go
@ -24,7 +24,7 @@ import (
 func TestTemplateInfoShortcode(t *testing.T) {
 	c := qt.New(t)
 	d := newD(c)
-	h := d.Tmpl.(tpl.TemplateHandler)
+	h := d.Tmpl.(tpl.TemplateManager)

 	c.Assert(h.AddTemplate("shortcodes/mytemplate.html", `
 {{ .Inner }}
				`@ -0,0 +1 @@`
				`<!DOCTYPE html><html><head><title>{{ .Permalink }}</title><link rel="canonical" href="{{ .Permalink }}"/><meta name="robots" content="noindex"><meta charset="utf-8" /><meta http-equiv="refresh" content="0; url={{ .Permalink }}" /></head></html>`