resources: Move resource interfaces into its own package

resources/resource_transformers/integrity/integrity.go

@@ -0,0 +1,106 @@
+// 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 integrity
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+	"hash"
+	"html/template"
+	"io"
+
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+const defaultHashAlgo = "sha256"
+
+// Client contains methods to fingerprint (cachebusting) and other integrity-related
+// methods.
+type Client struct {
+	rs *resources.Spec
+}
+
+// New creates a new Client with the given specification.
+func New(rs *resources.Spec) *Client {
+	return &Client{rs: rs}
+}
+
+type fingerprintTransformation struct {
+	algo string
+}
+
+func (t *fingerprintTransformation) Key() resources.ResourceTransformationKey {
+	return resources.NewResourceTransformationKey("fingerprint", t.algo)
+}
+
+// Transform creates a MD5 hash of the Resource content and inserts that hash before
+// the extension in the filename.
+func (t *fingerprintTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+	algo := t.algo
+
+	var h hash.Hash
+
+	switch algo {
+	case "md5":
+		h = md5.New()
+	case "sha256":
+		h = sha256.New()
+	case "sha512":
+		h = sha512.New()
+	default:
+		return fmt.Errorf("unsupported crypto algo: %q, use either md5, sha256 or sha512", algo)
+	}
+
+	io.Copy(io.MultiWriter(h, ctx.To), ctx.From)
+	d, err := digest(h)
+	if err != nil {
+		return err
+	}
+
+	ctx.Data["Integrity"] = integrity(algo, d)
+	ctx.AddOutPathIdentifier("." + hex.EncodeToString(d[:]))
+	return nil
+}
+
+// Fingerprint applies fingerprinting of the given resource and hash algorithm.
+// It defaults to sha256 if none given, and the options are md5, sha256 or sha512.
+// The same algo is used for both the fingerprinting part (aka cache busting) and
+// the base64-encoded Subresource Integrity hash, so you will have to stay away from
+// md5 if you plan to use both.
+// See https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity
+func (c *Client) Fingerprint(res resource.Resource, algo string) (resource.Resource, error) {
+	if algo == "" {
+		algo = defaultHashAlgo
+	}
+
+	return c.rs.Transform(
+		res,
+		&fingerprintTransformation{algo: algo},
+	)
+}
+
+func integrity(algo string, sum []byte) template.HTMLAttr {
+	encoded := base64.StdEncoding.EncodeToString(sum)
+	return template.HTMLAttr(algo + "-" + encoded)
+}
+
+func digest(h hash.Hash) ([]byte, error) {
+	sum := h.Sum(nil)
+	return sum, nil
+}

resources/resource_transformers/minifier/minify.go

@@ -0,0 +1,59 @@
+// 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 minifier
+
+import (
+	"github.com/gohugoio/hugo/minifiers"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+// Client for minification of Resource objects. Supported minfiers are:
+// css, html, js, json, svg and xml.
+type Client struct {
+	rs *resources.Spec
+	m  minifiers.Client
+}
+
+// New creates a new Client given a specification. Note that it is the media types
+// configured for the site that is used to match files to the correct minifier.
+func New(rs *resources.Spec) *Client {
+	return &Client{rs: rs, m: minifiers.New(rs.MediaTypes, rs.OutputFormats)}
+}
+
+type minifyTransformation struct {
+	rs *resources.Spec
+	m  minifiers.Client
+}
+
+func (t *minifyTransformation) Key() resources.ResourceTransformationKey {
+	return resources.NewResourceTransformationKey("minify")
+}
+
+func (t *minifyTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+	if err := t.m.Minify(ctx.InMediaType, ctx.To, ctx.From); err != nil {
+		return err
+	}
+	ctx.AddOutPathIdentifier(".min")
+	return nil
+}
+
+func (c *Client) Minify(res resource.Resource) (resource.Resource, error) {
+	return c.rs.Transform(
+		res,
+		&minifyTransformation{
+			rs: c.rs,
+			m:  c.m},
+	)
+}

resources/resource_transformers/postcss/postcss.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 postcss
+
+import (
+	"io"
+	"path/filepath"
+
+	"github.com/gohugoio/hugo/hugofs"
+	"github.com/pkg/errors"
+
+	"os"
+	"os/exec"
+
+	"github.com/mitchellh/mapstructure"
+
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+// Some of the options from https://github.com/postcss/postcss-cli
+type Options struct {
+
+	// Set a custom path to look for a config file.
+	Config string
+
+	NoMap bool `mapstructure:"no-map"` // Disable the default inline sourcemaps
+
+	// Options for when not using a config file
+	Use         string // List of postcss plugins to use
+	Parser      string //  Custom postcss parser
+	Stringifier string // Custom postcss stringifier
+	Syntax      string // Custom postcss syntax
+}
+
+func DecodeOptions(m map[string]interface{}) (opts Options, err error) {
+	if m == nil {
+		return
+	}
+	err = mapstructure.WeakDecode(m, &opts)
+	return
+}
+
+func (opts Options) toArgs() []string {
+	var args []string
+	if opts.NoMap {
+		args = append(args, "--no-map")
+	}
+	if opts.Use != "" {
+		args = append(args, "--use", opts.Use)
+	}
+	if opts.Parser != "" {
+		args = append(args, "--parser", opts.Parser)
+	}
+	if opts.Stringifier != "" {
+		args = append(args, "--stringifier", opts.Stringifier)
+	}
+	if opts.Syntax != "" {
+		args = append(args, "--syntax", opts.Syntax)
+	}
+	return args
+}
+
+// Client is the client used to do PostCSS transformations.
+type Client struct {
+	rs *resources.Spec
+}
+
+// New creates a new Client with the given specification.
+func New(rs *resources.Spec) *Client {
+	return &Client{rs: rs}
+}
+
+type postcssTransformation struct {
+	options Options
+	rs      *resources.Spec
+}
+
+func (t *postcssTransformation) Key() resources.ResourceTransformationKey {
+	return resources.NewResourceTransformationKey("postcss", t.options)
+}
+
+// Transform shells out to postcss-cli to do the heavy lifting.
+// For this to work, you need some additional tools. To install them globally:
+// npm install -g postcss-cli
+// npm install -g autoprefixer
+func (t *postcssTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+
+	const localPostCSSPath = "node_modules/postcss-cli/bin/"
+	const binaryName = "postcss"
+
+	// Try first in the project's node_modules.
+	csiBinPath := filepath.Join(t.rs.WorkingDir, localPostCSSPath, binaryName)
+
+	binary := csiBinPath
+
+	if _, err := exec.LookPath(binary); err != nil {
+		// Try PATH
+		binary = binaryName
+		if _, err := exec.LookPath(binary); err != nil {
+			// This may be on a CI server etc. Will fall back to pre-built assets.
+			return herrors.ErrFeatureNotAvailable
+		}
+	}
+
+	var configFile string
+	logger := t.rs.Logger
+
+	if t.options.Config != "" {
+		configFile = t.options.Config
+	} else {
+		configFile = "postcss.config.js"
+	}
+
+	configFile = filepath.Clean(configFile)
+
+	// We need an abolute filename to the config file.
+	if !filepath.IsAbs(configFile) {
+		// We resolve this against the virtual Work filesystem, to allow
+		// this config file to live in one of the themes if needed.
+		fi, err := t.rs.BaseFs.Work.Fs.Stat(configFile)
+		if err != nil {
+			if t.options.Config != "" {
+				// Only fail if the user specificed config file is not found.
+				return errors.Wrapf(err, "postcss config %q not found:", configFile)
+			}
+			configFile = ""
+		} else {
+			configFile = fi.(hugofs.RealFilenameInfo).RealFilename()
+		}
+	}
+
+	var cmdArgs []string
+
+	if configFile != "" {
+		logger.INFO.Println("postcss: use config file", configFile)
+		cmdArgs = []string{"--config", configFile}
+	}
+
+	if optArgs := t.options.toArgs(); len(optArgs) > 0 {
+		cmdArgs = append(cmdArgs, optArgs...)
+	}
+
+	cmd := exec.Command(binary, cmdArgs...)
+
+	cmd.Stdout = ctx.To
+	cmd.Stderr = os.Stderr
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	go func() {
+		defer stdin.Close()
+		io.Copy(stdin, ctx.From)
+	}()
+
+	err = cmd.Run()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Process transforms the given Resource with the PostCSS processor.
+func (c *Client) Process(res resource.Resource, options Options) (resource.Resource, error) {
+	return c.rs.Transform(
+		res,
+		&postcssTransformation{rs: c.rs, options: options},
+	)
+}

resources/resource_transformers/templates/execute_as_template.go

@@ -0,0 +1,76 @@
+// 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 templates contains functions for template processing of Resource objects.
+package templates
+
+import (
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+	"github.com/gohugoio/hugo/tpl"
+	"github.com/pkg/errors"
+)
+
+// Client contains methods to perform template processing of Resource objects.
+type Client struct {
+	rs *resources.Spec
+
+	textTemplate tpl.TemplateParseFinder
+}
+
+// New creates a new Client with the given specification.
+func New(rs *resources.Spec, 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}
+}
+
+type executeAsTemplateTransform struct {
+	rs           *resources.Spec
+	textTemplate tpl.TemplateParseFinder
+	targetPath   string
+	data         interface{}
+}
+
+func (t *executeAsTemplateTransform) Key() resources.ResourceTransformationKey {
+	return resources.NewResourceTransformationKey("execute-as-template", t.targetPath)
+}
+
+func (t *executeAsTemplateTransform) Transform(ctx *resources.ResourceTransformationCtx) error {
+	tplStr := helpers.ReaderToString(ctx.From)
+	templ, err := t.textTemplate.Parse(ctx.InPath, tplStr)
+	if err != nil {
+		return errors.Wrapf(err, "failed to parse Resource %q as Template:", ctx.InPath)
+	}
+
+	ctx.OutPath = t.targetPath
+
+	return templ.Execute(ctx.To, t.data)
+}
+
+func (c *Client) ExecuteAsTemplate(res resource.Resource, targetPath string, data interface{}) (resource.Resource, error) {
+	return c.rs.Transform(
+		res,
+		&executeAsTemplateTransform{
+			rs:           c.rs,
+			targetPath:   helpers.ToSlashTrimLeading(targetPath),
+			textTemplate: c.textTemplate,
+			data:         data,
+		},
+	)
+}

resources/resource_transformers/tocss/scss/client.go

@@ -0,0 +1,111 @@
+// 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 scss
+
+import (
+	"github.com/bep/go-tocss/scss"
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/hugolib/filesystems"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+
+	"github.com/mitchellh/mapstructure"
+)
+
+type Client struct {
+	rs     *resources.Spec
+	sfs    *filesystems.SourceFilesystem
+	workFs *filesystems.SourceFilesystem
+}
+
+func New(fs *filesystems.SourceFilesystem, rs *resources.Spec) (*Client, error) {
+	return &Client{sfs: fs, workFs: rs.BaseFs.Work, rs: rs}, nil
+}
+
+type Options struct {
+
+	// Hugo, will by default, just replace the extension of the source
+	// to .css, e.g. "scss/main.scss" becomes "scss/main.css". You can
+	// control this by setting this, e.g. "styles/main.css" will create
+	// a Resource with that as a base for RelPermalink etc.
+	TargetPath string
+
+	// Hugo automatically adds the entry directories (where the main.scss lives)
+	// for project and themes to the list of include paths sent to LibSASS.
+	// Any paths set in this setting will be appended. Note that these will be
+	// treated as relative to the working dir, i.e. no include paths outside the
+	// project/themes.
+	IncludePaths []string
+
+	// Default is nested.
+	// One of nested, expanded, compact, compressed.
+	OutputStyle string
+
+	// Precision of floating point math.
+	Precision int
+
+	// When enabled, Hugo will generate a source map.
+	EnableSourceMap bool
+}
+
+type options struct {
+	// The options we receive from the end user.
+	from Options
+
+	// The options we send to the SCSS library.
+	to scss.Options
+}
+
+func (c *Client) ToCSS(res resource.Resource, opts Options) (resource.Resource, error) {
+	internalOptions := options{
+		from: opts,
+	}
+
+	// Transfer values from client.
+	internalOptions.to.Precision = opts.Precision
+	internalOptions.to.OutputStyle = scss.OutputStyleFromString(opts.OutputStyle)
+
+	if internalOptions.to.Precision == 0 {
+		// bootstrap-sass requires 8 digits precision. The libsass default is 5.
+		// https://github.com/twbs/bootstrap-sass/blob/master/README.md#sass-number-precision
+		internalOptions.to.Precision = 8
+	}
+
+	return c.rs.Transform(
+		res,
+		&toCSSTransformation{c: c, options: internalOptions},
+	)
+}
+
+type toCSSTransformation struct {
+	c       *Client
+	options options
+}
+
+func (t *toCSSTransformation) Key() resources.ResourceTransformationKey {
+	return resources.NewResourceTransformationKey("tocss", t.options.from)
+}
+
+func DecodeOptions(m map[string]interface{}) (opts Options, err error) {
+	if m == nil {
+		return
+	}
+	err = mapstructure.WeakDecode(m, &opts)
+
+	if opts.TargetPath != "" {
+		opts.TargetPath = helpers.ToSlashTrimLeading(opts.TargetPath)
+	}
+
+	return
+}

resources/resource_transformers/tocss/scss/tocss.go

@@ -0,0 +1,173 @@
+// 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.
+
+// +build extended
+
+package scss
+
+import (
+	"fmt"
+	"io"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"github.com/bep/go-tocss/scss"
+	"github.com/bep/go-tocss/scss/libsass"
+	"github.com/bep/go-tocss/tocss"
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/hugofs"
+	"github.com/gohugoio/hugo/media"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/pkg/errors"
+)
+
+// Used in tests. This feature requires Hugo to be built with the extended tag.
+func Supports() bool {
+	return true
+}
+
+func (t *toCSSTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+	ctx.OutMediaType = media.CSSType
+
+	var outName string
+	if t.options.from.TargetPath != "" {
+		ctx.OutPath = t.options.from.TargetPath
+	} else {
+		ctx.ReplaceOutPathExtension(".css")
+	}
+
+	outName = path.Base(ctx.OutPath)
+
+	options := t.options
+	baseDir := path.Dir(ctx.SourcePath)
+	options.to.IncludePaths = t.c.sfs.RealDirs(baseDir)
+
+	// Append any workDir relative include paths
+	for _, ip := range options.from.IncludePaths {
+		options.to.IncludePaths = append(options.to.IncludePaths, t.c.workFs.RealDirs(filepath.Clean(ip))...)
+	}
+
+	// To allow for overrides of SCSS files anywhere in the project/theme hierarchy, we need
+	// to help libsass revolve the filename by looking in the composite filesystem first.
+	// We add the entry directories for both project and themes to the include paths list, but
+	// that only work for overrides on the top level.
+	options.to.ImportResolver = func(url string, prev string) (newUrl string, body string, resolved bool) {
+		// We get URL paths from LibSASS, but we need file paths.
+		url = filepath.FromSlash(url)
+		prev = filepath.FromSlash(prev)
+
+		var basePath string
+		urlDir := filepath.Dir(url)
+		var prevDir string
+		if prev == "stdin" {
+			prevDir = baseDir
+		} else {
+			prevDir = t.c.sfs.MakePathRelative(filepath.Dir(prev))
+			if prevDir == "" {
+				// Not a member of this filesystem. Let LibSASS handle it.
+				return "", "", false
+			}
+		}
+
+		basePath = filepath.Join(prevDir, urlDir)
+		name := filepath.Base(url)
+
+		// Libsass throws an error in cases where you have several possible candidates.
+		// We make this simpler and pick the first match.
+		var namePatterns []string
+		if strings.Contains(name, ".") {
+			namePatterns = []string{"_%s", "%s"}
+		} else if strings.HasPrefix(name, "_") {
+			namePatterns = []string{"_%s.scss", "_%s.sass"}
+		} else {
+			namePatterns = []string{"_%s.scss", "%s.scss", "_%s.sass", "%s.sass"}
+		}
+
+		name = strings.TrimPrefix(name, "_")
+
+		for _, namePattern := range namePatterns {
+			filenameToCheck := filepath.Join(basePath, fmt.Sprintf(namePattern, name))
+			fi, err := t.c.sfs.Fs.Stat(filenameToCheck)
+			if err == nil {
+				if fir, ok := fi.(hugofs.RealFilenameInfo); ok {
+					return fir.RealFilename(), "", true
+				}
+			}
+		}
+
+		// Not found, let LibSASS handle it
+		return "", "", false
+	}
+
+	if ctx.InMediaType.SubType == media.SASSType.SubType {
+		options.to.SassSyntax = true
+	}
+
+	if options.from.EnableSourceMap {
+
+		options.to.SourceMapFilename = outName + ".map"
+		options.to.SourceMapRoot = t.c.rs.WorkingDir
+
+		// Setting this to the relative input filename will get the source map
+		// more correct for the main entry path (main.scss typically), but
+		// it will mess up the import mappings. As a workaround, we do a replacement
+		// in the source map itself (see below).
+		//options.InputPath = inputPath
+		options.to.OutputPath = outName
+		options.to.SourceMapContents = true
+		options.to.OmitSourceMapURL = false
+		options.to.EnableEmbeddedSourceMap = false
+	}
+
+	res, err := t.c.toCSS(options.to, ctx.To, ctx.From)
+	if err != nil {
+		return err
+	}
+
+	if options.from.EnableSourceMap && res.SourceMapContent != "" {
+		sourcePath := t.c.sfs.RealFilename(ctx.SourcePath)
+
+		if strings.HasPrefix(sourcePath, t.c.rs.WorkingDir) {
+			sourcePath = strings.TrimPrefix(sourcePath, t.c.rs.WorkingDir+helpers.FilePathSeparator)
+		}
+
+		// This needs to be Unix-style slashes, even on Windows.
+		// See https://github.com/gohugoio/hugo/issues/4968
+		sourcePath = filepath.ToSlash(sourcePath)
+
+		// This is a workaround for what looks like a bug in Libsass. But
+		// getting this resolution correct in tools like Chrome Workspaces
+		// is important enough to go this extra mile.
+		mapContent := strings.Replace(res.SourceMapContent, `stdin",`, fmt.Sprintf("%s\",", sourcePath), 1)
+
+		return ctx.PublishSourceMap(mapContent)
+	}
+	return nil
+}
+
+func (c *Client) toCSS(options scss.Options, dst io.Writer, src io.Reader) (tocss.Result, error) {
+	var res tocss.Result
+
+	transpiler, err := libsass.New(options)
+	if err != nil {
+		return res, err
+	}
+
+	res, err = transpiler.Execute(dst, src)
+	if err != nil {
+		return res, errors.Wrap(err, "SCSS processing failed")
+	}
+
+	return res, nil
+}

resources/resource_transformers/tocss/scss/tocss_notavailable.go

@@ -0,0 +1,30 @@
+// 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.
+
+// +build !extended
+
+package scss
+
+import (
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/resources"
+)
+
+// Used in tests.
+func Supports() bool {
+	return false
+}
+
+func (t *toCSSTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+	return herrors.ErrFeatureNotAvailable
+}