tpl/transform: Add transform.Unmarshal func

Fixes #5428

cache/namedmemcache/named_cache.go

@@ -0,0 +1,84 @@
+// Copyright 2018 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 namedmemcache provides a memory cache with a named lock. This is suitable
+// for situations where creating the cached resource can be time consuming or otherwise
+// resource hungry, or in situations where a "once only per key" is a requirement.
+package namedmemcache
+
+import (
+	"sync"
+
+	"github.com/BurntSushi/locker"
+)
+
+// Cache holds the cached values.
+type Cache struct {
+	nlocker *locker.Locker
+	cache   map[string]cacheEntry
+	mu      sync.RWMutex
+}
+
+type cacheEntry struct {
+	value interface{}
+	err   error
+}
+
+// New creates a new cache.
+func New() *Cache {
+	return &Cache{
+		nlocker: locker.NewLocker(),
+		cache:   make(map[string]cacheEntry),
+	}
+}
+
+// Clear clears the cache state.
+func (c *Cache) Clear() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.cache = make(map[string]cacheEntry)
+	c.nlocker = locker.NewLocker()
+
+}
+
+// GetOrCreate tries to get the value with the given cache key, if not found
+// create will be called and cached.
+// This method is thread safe. It also guarantees that the create func for a given
+// key is invoced only once for this cache.
+func (c *Cache) GetOrCreate(key string, create func() (interface{}, error)) (interface{}, error) {
+	c.mu.RLock()
+	entry, found := c.cache[key]
+	c.mu.RUnlock()
+
+	if found {
+		return entry.value, entry.err
+	}
+
+	c.nlocker.Lock(key)
+	defer c.nlocker.Unlock(key)
+
+	// Double check
+	if entry, found := c.cache[key]; found {
+		return entry.value, entry.err
+	}
+
+	// Create it.
+	value, err := create()
+
+	c.mu.Lock()
+	c.cache[key] = cacheEntry{value: value, err: err}
+	c.mu.Unlock()
+
+	return value, err
+}

cache/namedmemcache/named_cache_test.go

@@ -0,0 +1,80 @@
+// Copyright 2018 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 namedmemcache
+
+import (
+	"fmt"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNamedCache(t *testing.T) {
+	t.Parallel()
+	assert := require.New(t)
+
+	cache := New()
+
+	counter := 0
+	create := func() (interface{}, error) {
+		counter++
+		return counter, nil
+	}
+
+	for i := 0; i < 5; i++ {
+		v1, err := cache.GetOrCreate("a1", create)
+		assert.NoError(err)
+		assert.Equal(1, v1)
+		v2, err := cache.GetOrCreate("a2", create)
+		assert.NoError(err)
+		assert.Equal(2, v2)
+	}
+
+	cache.Clear()
+
+	v3, err := cache.GetOrCreate("a2", create)
+	assert.NoError(err)
+	assert.Equal(3, v3)
+}
+
+func TestNamedCacheConcurrent(t *testing.T) {
+	t.Parallel()
+
+	assert := require.New(t)
+
+	var wg sync.WaitGroup
+
+	cache := New()
+
+	create := func(i int) func() (interface{}, error) {
+		return func() (interface{}, error) {
+			return i, nil
+		}
+	}
+
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for j := 0; j < 100; j++ {
+				id := fmt.Sprintf("id%d", j)
+				v, err := cache.GetOrCreate(id, create(j))
+				assert.NoError(err)
+				assert.Equal(j, v)
+			}
+		}()
+	}
+	wg.Wait()
+}

deps/deps.go

@@ -123,6 +123,9 @@ type Listeners struct {
 
 // Add adds a function to a Listeners instance.
 func (b *Listeners) Add(f func()) {
+	if b == nil {
+		return
+	}
 	b.Lock()
 	defer b.Unlock()
 	b.listeners = append(b.listeners, f)
@@ -192,6 +195,14 @@ func New(cfg DepsCfg) (*Deps, error) {
 		fs = hugofs.NewDefault(cfg.Language)
 	}
 
+	if cfg.MediaTypes == nil {
+		cfg.MediaTypes = media.DefaultTypes
+	}
+
+	if cfg.OutputFormats == nil {
+		cfg.OutputFormats = output.DefaultFormats
+	}
+
 	ps, err := helpers.NewPathSpec(fs, cfg.Language)
 
 	if err != nil {

helpers/general.go

@@ -394,11 +394,10 @@ func MD5FromFileFast(r io.ReadSeeker) (string, error) {
 	return hex.EncodeToString(h.Sum(nil)), nil
 }
 
-// MD5FromFile creates a MD5 hash from the given file.
+// MD5FromReader creates a MD5 hash from the given reader.
-// It will not close the file.
+func MD5FromReader(r io.Reader) (string, error) {
-func MD5FromFile(f afero.File) (string, error) {
 	h := md5.New()
-	if _, err := io.Copy(h, f); err != nil {
+	if _, err := io.Copy(h, r); err != nil {
 		return "", nil
 	}
 	return hex.EncodeToString(h.Sum(nil)), nil

helpers/general_test.go

@@ -272,7 +272,7 @@ func TestFastMD5FromFile(t *testing.T) {
 	req.NoError(err)
 	req.NotEqual(m3, m4)
 
-	m5, err := MD5FromFile(bf2)
+	m5, err := MD5FromReader(bf2)
 	req.NoError(err)
 	req.NotEqual(m4, m5)
 }
@@ -293,7 +293,7 @@ func BenchmarkMD5FromFileFast(b *testing.B) {
 				}
 				b.StartTimer()
 				if full {
-					if _, err := MD5FromFile(f); err != nil {
+					if _, err := MD5FromReader(f); err != nil {
 						b.Fatal(err)
 					}
 				} else {

hugolib/resource_chain_test.go

@@ -339,6 +339,16 @@ Publish 2: {{ $cssPublish2.Permalink }}
 			assert.False(b.CheckExists("public/inline.min.css"), "Inline content should not be copied to /public")
 		}},
 
+		{"unmarshal", func() bool { return true }, func(b *sitesBuilder) {
+			b.WithTemplates("home.html", `
+{{ $toml := "slogan = \"Hugo Rocks!\"" | resources.FromString "slogan.toml" | transform.Unmarshal }}
+Slogan: {{ $toml.slogan }}
+
+`)
+		}, func(b *sitesBuilder) {
+			b.AssertFileContent("public/index.html", `Slogan: Hugo Rocks!`)
+		}},
+
 		{"template", func() bool { return true }, func(b *sitesBuilder) {}, func(b *sitesBuilder) {
 		}},
 	}

media/mediaType.go

@@ -135,6 +135,8 @@ var (
 	XMLType        = Type{MainType: "application", SubType: "xml", Suffixes: []string{"xml"}, Delimiter: defaultDelimiter}
 	SVGType        = Type{MainType: "image", SubType: "svg", mimeSuffix: "xml", Suffixes: []string{"svg"}, Delimiter: defaultDelimiter}
 	TextType       = Type{MainType: "text", SubType: "plain", Suffixes: []string{"txt"}, Delimiter: defaultDelimiter}
+	TOMLType       = Type{MainType: "application", SubType: "toml", Suffixes: []string{"toml"}, Delimiter: defaultDelimiter}
+	YAMLType       = Type{MainType: "application", SubType: "yaml", Suffixes: []string{"yaml", "yml"}, Delimiter: defaultDelimiter}
 
 	OctetType = Type{MainType: "application", SubType: "octet-stream"}
 )
@@ -154,6 +156,8 @@ var DefaultTypes = Types{
 	SVGType,
 	TextType,
 	OctetType,
+	YAMLType,
+	TOMLType,
 }
 
 func init() {

media/mediaType_test.go

@@ -39,6 +39,8 @@ func TestDefaultTypes(t *testing.T) {
 		{SVGType, "image", "svg", "svg", "image/svg+xml", "image/svg+xml"},
 		{TextType, "text", "plain", "txt", "text/plain", "text/plain"},
 		{XMLType, "application", "xml", "xml", "application/xml", "application/xml"},
+		{TOMLType, "application", "toml", "toml", "application/toml", "application/toml"},
+		{YAMLType, "application", "yaml", "yaml", "application/yaml", "application/yaml"},
 	} {
 		require.Equal(t, test.expectedMainType, test.tp.MainType)
 		require.Equal(t, test.expectedSubType, test.tp.SubType)
@@ -50,6 +52,8 @@ func TestDefaultTypes(t *testing.T) {
 
 	}
 
+	require.Equal(t, 15, len(DefaultTypes))
+
 }
 
 func TestGetByType(t *testing.T) {

parser/metadecoders/format.go

@@ -17,6 +17,8 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/gohugoio/hugo/media"
+
 	"github.com/gohugoio/hugo/parser/pageparser"
 )
 
@@ -55,6 +57,18 @@ func FormatFromString(formatStr string) Format {
 
 }
 
+// FormatFromMediaType gets the Format given a MIME type, empty string
+// if unknown.
+func FormatFromMediaType(m media.Type) Format {
+	for _, suffix := range m.Suffixes {
+		if f := FormatFromString(suffix); f != "" {
+			return f
+		}
+	}
+
+	return ""
+}
+
 // FormatFromFrontMatterType will return empty if not supported.
 func FormatFromFrontMatterType(typ pageparser.ItemType) Format {
 	switch typ {
@@ -70,3 +84,39 @@ func FormatFromFrontMatterType(typ pageparser.ItemType) Format {
 		return ""
 	}
 }
+
+// FormatFromContentString tries to detect the format (JSON, YAML or TOML)
+// in the given string.
+// It return an empty string if no format could be detected.
+func FormatFromContentString(data string) Format {
+	jsonIdx := strings.Index(data, "{")
+	yamlIdx := strings.Index(data, ":")
+	tomlIdx := strings.Index(data, "=")
+
+	if isLowerIndexThan(jsonIdx, yamlIdx, tomlIdx) {
+		return JSON
+	}
+
+	if isLowerIndexThan(yamlIdx, tomlIdx) {
+		return YAML
+	}
+
+	if tomlIdx != -1 {
+		return TOML
+	}
+
+	return ""
+}
+
+func isLowerIndexThan(first int, others ...int) bool {
+	if first == -1 {
+		return false
+	}
+	for _, other := range others {
+		if other != -1 && other < first {
+			return false
+		}
+	}
+
+	return true
+}

parser/metadecoders/format_test.go

@@ -17,6 +17,8 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/gohugoio/hugo/media"
+
 	"github.com/gohugoio/hugo/parser/pageparser"
 
 	"github.com/stretchr/testify/require"
@@ -41,6 +43,21 @@ func TestFormatFromString(t *testing.T) {
 	}
 }
 
+func TestFormatFromMediaType(t *testing.T) {
+	assert := require.New(t)
+	for i, test := range []struct {
+		m      media.Type
+		expect Format
+	}{
+		{media.JSONType, JSON},
+		{media.YAMLType, YAML},
+		{media.TOMLType, TOML},
+		{media.CalendarType, ""},
+	} {
+		assert.Equal(test.expect, FormatFromMediaType(test.m), fmt.Sprintf("t%d", i))
+	}
+}
+
 func TestFormatFromFrontMatterType(t *testing.T) {
 	assert := require.New(t)
 	for i, test := range []struct {
@@ -56,3 +73,28 @@ func TestFormatFromFrontMatterType(t *testing.T) {
 		assert.Equal(test.expect, FormatFromFrontMatterType(test.typ), fmt.Sprintf("t%d", i))
 	}
 }
+
+func TestFormatFromContentString(t *testing.T) {
+	t.Parallel()
+	assert := require.New(t)
+
+	for i, test := range []struct {
+		data   string
+		expect interface{}
+	}{
+		{`foo = "bar"`, TOML},
+		{`   foo = "bar"`, TOML},
+		{`foo="bar"`, TOML},
+		{`foo: "bar"`, YAML},
+		{`foo:"bar"`, YAML},
+		{`{ "foo": "bar"`, JSON},
+		{`asdfasdf`, Format("")},
+		{``, Format("")},
+	} {
+		errMsg := fmt.Sprintf("[%d] %s", i, test.data)
+
+		result := FormatFromContentString(test.data)
+
+		assert.Equal(test.expect, result, errMsg)
+	}
+}

resource/resource.go

@@ -50,6 +50,7 @@ var (
 	_ ResourcesLanguageMerger = (*Resources)(nil)
 	_ permalinker             = (*genericResource)(nil)
 	_ collections.Slicer      = (*genericResource)(nil)
+	_ Identifier              = (*genericResource)(nil)
 )
 
 var noData = make(map[string]interface{})
@@ -76,6 +77,8 @@ type Cloner interface {
 
 // Resource represents a linkable resource, i.e. a content page, image etc.
 type Resource interface {
+	resourceBase
+
 	// Permalink represents the absolute link to this resource.
 	Permalink() string
 
@@ -87,9 +90,6 @@ type Resource interface {
 	// For content pages, this value is "page".
 	ResourceType() string
 
-	// MediaType is this resource's MIME type.
-	MediaType() media.Type
-
 	// Name is the logical name of this resource. This can be set in the front matter
 	// metadata for this resource. If not set, Hugo will assign a value.
 	// This will in most cases be the base filename.
@@ -109,6 +109,13 @@ type Resource interface {
 	Params() map[string]interface{}
 }
 
+// resourceBase pulls out the minimal set of operations to define a Resource,
+// to simplify testing etc.
+type resourceBase interface {
+	// MediaType is this resource's MIME type.
+	MediaType() media.Type
+}
+
 // ResourcesLanguageMerger describes an interface for merging resources from a
 // different language.
 type ResourcesLanguageMerger interface {
@@ -121,12 +128,17 @@ type translatedResource interface {
 	TranslationKey() string
 }
 
+// Identifier identifies a resource.
+type Identifier interface {
+	Key() string
+}
+
 // ContentResource represents a Resource that provides a way to get to its content.
 // Most Resource types in Hugo implements this interface, including Page.
 // This should be used with care, as it will read the file content into memory, but it
 // should be cached as effectively as possible by the implementation.
 type ContentResource interface {
-	Resource
+	resourceBase
 
 	// Content returns this resource's content. It will be equivalent to reading the content
 	// that RelPermalink points to in the published folder.
@@ -143,7 +155,7 @@ type OpenReadSeekCloser func() (hugio.ReadSeekCloser, error)
 
 // ReadSeekCloserResource is a Resource that supports loading its content.
 type ReadSeekCloserResource interface {
-	Resource
+	resourceBase
 	ReadSeekCloser() (hugio.ReadSeekCloser, error)
 }
 
@@ -716,6 +728,10 @@ func (l *genericResource) RelPermalink() string {
 	return l.relPermalinkFor(l.relTargetDirFile.path())
 }
 
+func (l *genericResource) Key() string {
+	return l.relTargetDirFile.path()
+}
+
 func (l *genericResource) relPermalinkFor(target string) string {
 	return l.relPermalinkForRel(target, false)
 

resource/resource_test.go

@@ -50,6 +50,7 @@ func TestGenericResourceWithLinkFacory(t *testing.T) {
 
 	assert.Equal("https://example.com/foo/foo.css", r.Permalink())
 	assert.Equal("/foo/foo.css", r.RelPermalink())
+	assert.Equal("foo.css", r.Key())
 	assert.Equal("css", r.ResourceType())
 }
 

resource/transform.go

@@ -38,6 +38,7 @@ var (
 	_ ContentResource        = (*transformedResource)(nil)
 	_ ReadSeekCloserResource = (*transformedResource)(nil)
 	_ collections.Slicer     = (*transformedResource)(nil)
+	_ Identifier             = (*transformedResource)(nil)
 )
 
 func (s *Spec) Transform(r Resource, t ResourceTransformation) (Resource, error) {
@@ -249,6 +250,13 @@ func (r *transformedResource) MediaType() media.Type {
 	return m
 }
 
+func (r *transformedResource) Key() string {
+	if err := r.initTransform(false, false); err != nil {
+		return ""
+	}
+	return r.linker.relPermalinkFor(r.Target)
+}
+
 func (r *transformedResource) Permalink() string {
 	if err := r.initTransform(false, true); err != nil {
 		return ""
@@ -481,8 +489,8 @@ func (r *transformedResource) transform(setContent, publish bool) (err error) {
 	}
 
 	return nil
-
 }
+
 func (r *transformedResource) initTransform(setContent, publish bool) error {
 	r.transformInit.Do(func() {
 		r.published = publish

tpl/transform/init.go

@@ -95,6 +95,14 @@ func init() {
 			},
 		)
 
+		ns.AddMethodMapping(ctx.Unmarshal,
+			[]string{"unmarshal"},
+			[][2]string{
+				{`{{ "hello = \"Hello World\"" | transform.Unmarshal }}`, "map[hello:Hello World]"},
+				{`{{ "hello = \"Hello World\"" | resources.FromString "data/greetings.toml" | transform.Unmarshal }}`, "map[hello:Hello World]"},
+			},
+		)
+
 		return ns
 
 	}

tpl/transform/remarshal.go

@@ -2,9 +2,10 @@ package transform
 
 import (
 	"bytes"
-	"errors"
 	"strings"
 
+	"github.com/pkg/errors"
+
 	"github.com/gohugoio/hugo/parser"
 	"github.com/gohugoio/hugo/parser/metadecoders"
 	"github.com/spf13/cast"
@@ -34,9 +35,9 @@ func (ns *Namespace) Remarshal(format string, data interface{}) (string, error)
 		return "", err
 	}
 
-	fromFormat, err := detectFormat(from)
+	fromFormat := metadecoders.FormatFromContentString(from)
-	if err != nil {
+	if fromFormat == "" {
-		return "", err
+		return "", errors.New("failed to detect format from content")
 	}
 
 	meta, err := metadecoders.UnmarshalToMap([]byte(from), fromFormat)
@@ -56,24 +57,3 @@ func toFormatMark(format string) (metadecoders.Format, error) {
 
 	return "", errors.New("failed to detect target data serialization format")
 }
-
-func detectFormat(data string) (metadecoders.Format, error) {
-	jsonIdx := strings.Index(data, "{")
-	yamlIdx := strings.Index(data, ":")
-	tomlIdx := strings.Index(data, "=")
-
-	if jsonIdx != -1 && (yamlIdx == -1 || jsonIdx < yamlIdx) && (tomlIdx == -1 || jsonIdx < tomlIdx) {
-		return metadecoders.JSON, nil
-	}
-
-	if yamlIdx != -1 && (tomlIdx == -1 || yamlIdx < tomlIdx) {
-		return metadecoders.YAML, nil
-	}
-
-	if tomlIdx != -1 {
-		return metadecoders.TOML, nil
-	}
-
-	return "", errors.New("failed to detect data serialization format")
-
-}

tpl/transform/remarshal_test.go

@@ -18,7 +18,6 @@ import (
 	"testing"
 
 	"github.com/gohugoio/hugo/helpers"
-	"github.com/gohugoio/hugo/parser/metadecoders"
 	"github.com/spf13/viper"
 	"github.com/stretchr/testify/require"
 )
@@ -171,34 +170,3 @@ func TestTestRemarshalError(t *testing.T) {
 	assert.Error(err)
 
 }
-
-func TestRemarshalDetectFormat(t *testing.T) {
-	t.Parallel()
-	assert := require.New(t)
-
-	for i, test := range []struct {
-		data   string
-		expect interface{}
-	}{
-		{`foo = "bar"`, metadecoders.TOML},
-		{`   foo = "bar"`, metadecoders.TOML},
-		{`foo="bar"`, metadecoders.TOML},
-		{`foo: "bar"`, metadecoders.YAML},
-		{`foo:"bar"`, metadecoders.YAML},
-		{`{ "foo": "bar"`, metadecoders.JSON},
-		{`asdfasdf`, false},
-		{``, false},
-	} {
-		errMsg := fmt.Sprintf("[%d] %s", i, test.data)
-
-		result, err := detectFormat(test.data)
-
-		if b, ok := test.expect.(bool); ok && !b {
-			assert.Error(err, errMsg)
-			continue
-		}
-
-		assert.NoError(err, errMsg)
-		assert.Equal(test.expect, result)
-	}
-}

tpl/transform/transform.go

@@ -19,6 +19,8 @@ import (
 	"html"
 	"html/template"
 
+	"github.com/gohugoio/hugo/cache/namedmemcache"
+
 	"github.com/gohugoio/hugo/deps"
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/spf13/cast"
@@ -26,14 +28,22 @@ import (
 
 // New returns a new instance of the transform-namespaced template functions.
 func New(deps *deps.Deps) *Namespace {
+	cache := namedmemcache.New()
+	deps.BuildStartListeners.Add(
+		func() {
+			cache.Clear()
+		})
+
 	return &Namespace{
-		deps: deps,
+		cache: cache,
+		deps:  deps,
 	}
 }
 
 // Namespace provides template functions for the "transform" namespace.
 type Namespace struct {
-	deps *deps.Deps
+	cache *namedmemcache.Cache
+	deps  *deps.Deps
 }
 
 // Emojify returns a copy of s with all emoji codes replaced with actual emojis.

tpl/transform/transform_test.go

@@ -34,7 +34,6 @@ func TestEmojify(t *testing.T) {
 	t.Parallel()
 
 	v := viper.New()
-	v.Set("contentDir", "content")
 	ns := New(newDeps(v))
 
 	for i, test := range []struct {
@@ -215,7 +214,6 @@ func TestPlainify(t *testing.T) {
 	t.Parallel()
 
 	v := viper.New()
-	v.Set("contentDir", "content")
 	ns := New(newDeps(v))
 
 	for i, test := range []struct {
@@ -241,8 +239,11 @@ func TestPlainify(t *testing.T) {
 }
 
 func newDeps(cfg config.Provider) *deps.Deps {
+	cfg.Set("contentDir", "content")
+	cfg.Set("i18nDir", "i18n")
+
 	l := langs.NewLanguage("en", cfg)
-	l.Set("i18nDir", "i18n")
+
 	cs, err := helpers.NewContentSpec(l)
 	if err != nil {
 		panic(err)

tpl/transform/unmarshal.go

@@ -0,0 +1,98 @@
+// Copyright 2018 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 transform
+
+import (
+	"io/ioutil"
+
+	"github.com/gohugoio/hugo/common/hugio"
+
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/parser/metadecoders"
+	"github.com/gohugoio/hugo/resource"
+	"github.com/pkg/errors"
+
+	"github.com/spf13/cast"
+)
+
+// Unmarshal unmarshals the data given, which can be either a string
+// or a Resource. Supported formats are JSON, TOML and YAML.
+func (ns *Namespace) Unmarshal(data interface{}) (interface{}, error) {
+
+	// All the relevant Resource types implements ReadSeekCloserResource,
+	// which should be the most effective way to get the content.
+	if r, ok := data.(resource.ReadSeekCloserResource); ok {
+		var key string
+		var reader hugio.ReadSeekCloser
+
+		if k, ok := r.(resource.Identifier); ok {
+			key = k.Key()
+		}
+
+		if key == "" {
+			reader, err := r.ReadSeekCloser()
+			if err != nil {
+				return nil, err
+			}
+			defer reader.Close()
+
+			key, err = helpers.MD5FromReader(reader)
+			if err != nil {
+				return nil, err
+			}
+
+			reader.Seek(0, 0)
+		}
+
+		return ns.cache.GetOrCreate(key, func() (interface{}, error) {
+			f := metadecoders.FormatFromMediaType(r.MediaType())
+			if f == "" {
+				return nil, errors.Errorf("MIME %q not supported", r.MediaType())
+			}
+
+			if reader == nil {
+				var err error
+				reader, err = r.ReadSeekCloser()
+				if err != nil {
+					return nil, err
+				}
+				defer reader.Close()
+			}
+
+			b, err := ioutil.ReadAll(reader)
+			if err != nil {
+				return nil, err
+			}
+
+			return metadecoders.Unmarshal(b, f)
+		})
+
+	}
+
+	dataStr, err := cast.ToStringE(data)
+	if err != nil {
+		return nil, errors.Errorf("type %T not supported", data)
+	}
+
+	key := helpers.MD5String(dataStr)
+
+	return ns.cache.GetOrCreate(key, func() (interface{}, error) {
+		f := metadecoders.FormatFromContentString(dataStr)
+		if f == "" {
+			return nil, errors.New("unknown format")
+		}
+
+		return metadecoders.Unmarshal([]byte(dataStr), f)
+	})
+}

tpl/transform/unmarshal_test.go

@@ -0,0 +1,185 @@
+// Copyright 2018 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 transform
+
+import (
+	"fmt"
+	"math/rand"
+	"strings"
+	"testing"
+
+	"github.com/gohugoio/hugo/common/hugio"
+
+	"github.com/gohugoio/hugo/media"
+
+	"github.com/gohugoio/hugo/resource"
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/require"
+)
+
+const (
+	testJSON = `
+	
+{
+    "ROOT_KEY": {
+        "title": "example glossary",
+		"GlossDiv": {
+            "title": "S",
+			"GlossList": {
+                "GlossEntry": {
+                    "ID": "SGML",
+					"SortAs": "SGML",
+					"GlossTerm": "Standard Generalized Markup Language",
+					"Acronym": "SGML",
+					"Abbrev": "ISO 8879:1986",
+					"GlossDef": {
+                        "para": "A meta-markup language, used to create markup languages such as DocBook.",
+						"GlossSeeAlso": ["GML", "XML"]
+                    },
+					"GlossSee": "markup"
+                }
+            }
+        }
+    }
+}
+
+	`
+)
+
+var _ resource.ReadSeekCloserResource = (*testContentResource)(nil)
+
+type testContentResource struct {
+	content string
+	mime    media.Type
+
+	key string
+}
+
+func (t testContentResource) ReadSeekCloser() (hugio.ReadSeekCloser, error) {
+	return hugio.NewReadSeekerNoOpCloserFromString(t.content), nil
+}
+
+func (t testContentResource) MediaType() media.Type {
+	return t.mime
+}
+
+func (t testContentResource) Key() string {
+	return t.key
+}
+
+func TestUnmarshal(t *testing.T) {
+
+	v := viper.New()
+	ns := New(newDeps(v))
+	assert := require.New(t)
+
+	assertSlogan := func(m map[string]interface{}) {
+		assert.Equal("Hugo Rocks!", m["slogan"])
+	}
+
+	for i, test := range []struct {
+		data   interface{}
+		expect interface{}
+	}{
+		{`{ "slogan": "Hugo Rocks!" }`, func(m map[string]interface{}) {
+			assertSlogan(m)
+		}},
+		{`slogan: "Hugo Rocks!"`, func(m map[string]interface{}) {
+			assertSlogan(m)
+		}},
+		{`slogan = "Hugo Rocks!"`, func(m map[string]interface{}) {
+			assertSlogan(m)
+		}},
+		{testContentResource{content: `slogan: "Hugo Rocks!"`, mime: media.YAMLType}, func(m map[string]interface{}) {
+			assertSlogan(m)
+		}},
+		{testContentResource{content: `{ "slogan": "Hugo Rocks!" }`, mime: media.JSONType}, func(m map[string]interface{}) {
+			assertSlogan(m)
+		}},
+		{testContentResource{content: `slogan = "Hugo Rocks!"`, mime: media.TOMLType}, func(m map[string]interface{}) {
+			assertSlogan(m)
+		}},
+		// errors
+		{"thisisnotavaliddataformat", false},
+		{testContentResource{content: `invalid&toml"`, mime: media.TOMLType}, false},
+		{testContentResource{content: `unsupported: MIME"`, mime: media.CalendarType}, false},
+		{"thisisnotavaliddataformat", false},
+		{`{ notjson }`, false},
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d]", i)
+
+		result, err := ns.Unmarshal(test.data)
+
+		if b, ok := test.expect.(bool); ok && !b {
+			assert.Error(err, errMsg)
+		} else if fn, ok := test.expect.(func(m map[string]interface{})); ok {
+			assert.NoError(err, errMsg)
+			m, ok := result.(map[string]interface{})
+			assert.True(ok, errMsg)
+			fn(m)
+		} else {
+			assert.NoError(err, errMsg)
+			assert.Equal(test.expect, result, errMsg)
+		}
+
+	}
+}
+
+func BenchmarkUnmarshalString(b *testing.B) {
+	v := viper.New()
+	ns := New(newDeps(v))
+
+	const numJsons = 100
+
+	var jsons [numJsons]string
+	for i := 0; i < numJsons; i++ {
+		jsons[i] = strings.Replace(testJSON, "ROOT_KEY", fmt.Sprintf("root%d", i), 1)
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		result, err := ns.Unmarshal(jsons[rand.Intn(numJsons)])
+		if err != nil {
+			b.Fatal(err)
+		}
+		if result == nil {
+			b.Fatal("no result")
+		}
+	}
+}
+
+func BenchmarkUnmarshalResource(b *testing.B) {
+	v := viper.New()
+	ns := New(newDeps(v))
+
+	const numJsons = 100
+
+	var jsons [numJsons]testContentResource
+	for i := 0; i < numJsons; i++ {
+		key := fmt.Sprintf("root%d", i)
+		jsons[i] = testContentResource{key: key, content: strings.Replace(testJSON, "ROOT_KEY", key, 1), mime: media.JSONType}
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		result, err := ns.Unmarshal(jsons[rand.Intn(numJsons)])
+		if err != nil {
+			b.Fatal(err)
+		}
+		if result == nil {
+			b.Fatal("no result")
+		}
+	}
+}