Refactor layout resolve to a descriptor/adapter pattern

hugolib/page.go

@@ -204,42 +204,24 @@ type Page struct {
 	// This is the PageOutput that represents the first item in outputFormats.
 	// Use with care, as there are potential for inifinite loops.
 	mainPageOutput *PageOutput
-
-	// Used to pick the correct template(s)
-	layoutIdentifier pageLayoutIdentifier
 }
 
-// Implements layout.LayoutIdentifier
-type pageLayoutIdentifier struct {
-	*Page
-}
+func (p *Page) createLayoutDescriptor() output.LayoutDescriptor {
+	var section string
 
-// PageKind returns the page's kind.
-func (p pageLayoutIdentifier) PageKind() string {
-	return p.Kind
-}
-
-// PageLayout returns the page's layout, if set.
-func (p pageLayoutIdentifier) PageLayout() string {
-	return p.Layout
-}
-
-// PageType returns the page's type, if set.
-func (p pageLayoutIdentifier) PageType() string {
-	return p.Type()
-}
-
-// PageType returns the page's section in layout terms.
-// This will be empty for regular pages, the section for section pages,
-// and the singular term for taxonomy and taxonomy terms pages.
-func (p pageLayoutIdentifier) PageSection() string {
 	switch p.Kind {
 	case KindSection:
-		return p.sections[0]
+		section = p.sections[0]
 	case KindTaxonomy, KindTaxonomyTerm:
-		return p.s.taxonomiesPluralSingular[p.sections[0]]
+		section = p.s.taxonomiesPluralSingular[p.sections[0]]
 	default:
-		return ""
+	}
+
+	return output.LayoutDescriptor{
+		Kind:    p.Kind,
+		Type:    p.Type(),
+		Layout:  p.Layout,
+		Section: section,
 	}
 }
 
@@ -642,7 +624,6 @@ func (s *Site) newPage(filename string) *Page {
 		Site:         &s.Info,
 		s:            s,
 	}
-	p.layoutIdentifier = pageLayoutIdentifier{p}
 
 	s.Log.DEBUG.Println("Reading from", p.File.Path())
 	return p
@@ -682,7 +663,10 @@ func (p *Page) layouts(layouts ...string) []string {
 		layoutOverride = layouts[0]
 	}
 
-	return p.s.layoutHandler.For(p.layoutIdentifier, layoutOverride, output.HTMLType)
+	return p.s.layoutHandler.For(
+		p.createLayoutDescriptor(),
+		layoutOverride,
+		output.HTMLType)
 }
 
 // TODO(bep) consolidate and test these KindHome switches (see other layouts methods)s

hugolib/page_test.go

@@ -1361,7 +1361,6 @@ func TestIndexPageSimpleMethods(t *testing.T) {
 		{func(n *Page) bool { return n.Scratch() != nil }},
 		{func(n *Page) bool { return n.Hugo() != nil }},
 		{func(n *Page) bool { return n.Now().Unix() == time.Now().Unix() }},
-		{func(n *Page) bool { return n.layoutIdentifier.Kind == KindHome }},
 	} {
 
 		n := s.newHomePage()

hugolib/site.go

@@ -1661,7 +1661,7 @@ func (s *Site) kindFromSections(sections []string) string {
 }
 
 func (s *Site) layouts(p *PageOutput) []string {
-	return s.layoutHandler.For(p.layoutIdentifier, "", p.outputFormat)
+	return s.layoutHandler.For(p.createLayoutDescriptor(), "", p.outputFormat)
 }
 
 func (s *Site) preparePages() error {
@@ -2062,7 +2062,6 @@ func (s *Site) newNodePage(typ string) *Page {
 		Site:     &s.Info,
 		s:        s}
 	p.outputFormats = p.s.defaultOutputDefinitions.ForKind(typ)
-	p.layoutIdentifier = pageLayoutIdentifier{p}
 	return p
 
 }

output/layout.go

@@ -19,12 +19,13 @@ import (
 	"strings"
 )
 
-// LayoutIdentifier is used to pick the correct layout for a piece of content.
-type LayoutIdentifier interface {
-	PageType() string
-	PageSection() string // TODO(bep) name
-	PageKind() string
-	PageLayout() string
+// LayoutDescriptor describes how a layout should be chosen. This is
+// typically built from a Page.
+type LayoutDescriptor struct {
+	Type    string
+	Section string
+	Kind    string
+	Layout  string
 }
 
 // Layout calculates the layout template to use to render a given output type.
@@ -60,27 +61,27 @@ indexes/indexes.NAME.SUFFIX indexes/indexes.SUFFIX
 `
 )
 
-func (l *LayoutHandler) For(id LayoutIdentifier, layoutOverride string, f Format) []string {
+func (l *LayoutHandler) For(d LayoutDescriptor, layoutOverride string, f Format) []string {
 	var layouts []string
 
-	layout := id.PageLayout()
+	layout := d.Layout
 
 	if layoutOverride != "" {
 		layout = layoutOverride
 	}
 
-	switch id.PageKind() {
+	switch d.Kind {
 	// TODO(bep) move the Kind constants some common place.
 	case "home":
-		layouts = resolveTemplate(layoutsHome, id, f)
+		layouts = resolveTemplate(layoutsHome, d, f)
 	case "section":
-		layouts = resolveTemplate(layoutsSection, id, f)
+		layouts = resolveTemplate(layoutsSection, d, f)
 	case "taxonomy":
-		layouts = resolveTemplate(layoutTaxonomy, id, f)
+		layouts = resolveTemplate(layoutTaxonomy, d, f)
 	case "taxonomyTerm":
-		layouts = resolveTemplate(layoutTaxonomyTerm, id, f)
+		layouts = resolveTemplate(layoutTaxonomyTerm, d, f)
 	case "page":
-		layouts = regularPageLayouts(id.PageType(), layout, f)
+		layouts = regularPageLayouts(d.Type, layout, f)
 	}
 
 	if l.hasTheme {
@@ -112,11 +113,11 @@ func (l *LayoutHandler) For(id LayoutIdentifier, layoutOverride string, f Format
 	return layouts
 }
 
-func resolveTemplate(templ string, id LayoutIdentifier, f Format) []string {
+func resolveTemplate(templ string, d LayoutDescriptor, f Format) []string {
 	return strings.Fields(replaceKeyValues(templ,
 		"SUFFIX", f.MediaType.Suffix,
 		"NAME", strings.ToLower(f.Name),
-		"SECTION", id.PageSection()))
+		"SECTION", d.Section))
 }
 
 func replaceKeyValues(s string, oldNew ...string) string {

output/layout_test.go

@@ -21,29 +21,6 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-type testLayoutIdentifier struct {
-	pageKind    string
-	pageSection string
-	pageLayout  string
-	pageType    string
-}
-
-func (l testLayoutIdentifier) PageKind() string {
-	return l.pageKind
-}
-
-func (l testLayoutIdentifier) PageLayout() string {
-	return l.pageLayout
-}
-
-func (l testLayoutIdentifier) PageType() string {
-	return l.pageType
-}
-
-func (l testLayoutIdentifier) PageSection() string {
-	return l.pageSection
-}
-
 var ampType = Format{
 	Name:      "AMP",
 	MediaType: media.HTMLType,
@@ -54,35 +31,35 @@ func TestLayout(t *testing.T) {
 
 	for _, this := range []struct {
 		name           string
-		li             testLayoutIdentifier
+		d              LayoutDescriptor
 		hasTheme       bool
 		layoutOverride string
 		tp             Format
 		expect         []string
 	}{
-		{"Home", testLayoutIdentifier{"home", "", "", ""}, true, "", ampType,
+		{"Home", LayoutDescriptor{Kind: "home"}, true, "", ampType,
 			[]string{"index.amp.html", "index.html", "_default/list.amp.html", "_default/list.html", "theme/index.amp.html", "theme/index.html"}},
-		{"Section", testLayoutIdentifier{"section", "sect1", "", ""}, false, "", ampType,
+		{"Section", LayoutDescriptor{Kind: "section", Section: "sect1"}, false, "", ampType,
 			[]string{"section/sect1.amp.html", "section/sect1.html"}},
-		{"Taxonomy", testLayoutIdentifier{"taxonomy", "tag", "", ""}, false, "", ampType,
+		{"Taxonomy", LayoutDescriptor{Kind: "taxonomy", Section: "tag"}, false, "", ampType,
 			[]string{"taxonomy/tag.amp.html", "taxonomy/tag.html"}},
-		{"Taxonomy term", testLayoutIdentifier{"taxonomyTerm", "categories", "", ""}, false, "", ampType,
+		{"Taxonomy term", LayoutDescriptor{Kind: "taxonomyTerm", Section: "categories"}, false, "", ampType,
 			[]string{"taxonomy/categories.terms.amp.html", "taxonomy/categories.terms.html", "_default/terms.amp.html"}},
-		{"Page", testLayoutIdentifier{"page", "", "", ""}, true, "", ampType,
+		{"Page", LayoutDescriptor{Kind: "page"}, true, "", ampType,
 			[]string{"_default/single.amp.html", "_default/single.html", "theme/_default/single.amp.html"}},
-		{"Page with layout", testLayoutIdentifier{"page", "", "mylayout", ""}, false, "", ampType,
+		{"Page with layout", LayoutDescriptor{Kind: "page", Layout: "mylayout"}, false, "", ampType,
 			[]string{"_default/mylayout.amp.html", "_default/mylayout.html"}},
-		{"Page with layout and type", testLayoutIdentifier{"page", "", "mylayout", "myttype"}, false, "", ampType,
+		{"Page with layout and type", LayoutDescriptor{Kind: "page", Layout: "mylayout", Type: "myttype"}, false, "", ampType,
 			[]string{"myttype/mylayout.amp.html", "myttype/mylayout.html", "_default/mylayout.amp.html"}},
-		{"Page with layout and type with subtype", testLayoutIdentifier{"page", "", "mylayout", "myttype/mysubtype"}, false, "", ampType,
+		{"Page with layout and type with subtype", LayoutDescriptor{Kind: "page", Layout: "mylayout", Type: "myttype/mysubtype"}, false, "", ampType,
 			[]string{"myttype/mysubtype/mylayout.amp.html", "myttype/mysubtype/mylayout.html", "myttype/mylayout.amp.html"}},
-		{"Page with overridden layout", testLayoutIdentifier{"page", "", "mylayout", "myttype"}, false, "myotherlayout", ampType,
+		{"Page with overridden layout", LayoutDescriptor{Kind: "page", Layout: "mylayout", Type: "myttype"}, false, "myotherlayout", ampType,
 			[]string{"myttype/myotherlayout.amp.html", "myttype/myotherlayout.html"}},
 	} {
 		t.Run(this.name, func(t *testing.T) {
 			l := NewLayoutHandler(this.hasTheme)
 
-			layouts := l.For(this.li, this.layoutOverride, this.tp)
+			layouts := l.For(this.d, this.layoutOverride, this.tp)
 
 			require.NotNil(t, layouts)
 			require.True(t, len(layouts) >= len(this.expect))