Add Dart Sass support

But note that the Dart Sass Embedded Protocol is still in beta (beta 5), a main release scheduled for Q1 2021.

Fixes #7380
Fixes #8102

resources/resource_transformers/tocss/dartsass/transform.go

@@ -0,0 +1,222 @@
+// Copyright 2020 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 dartsass
+
+import (
+	"fmt"
+	"io"
+	"net/url"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"github.com/cli/safeexec"
+
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/htesting"
+	"github.com/gohugoio/hugo/media"
+
+	"github.com/gohugoio/hugo/resources"
+
+	"github.com/gohugoio/hugo/resources/internal"
+
+	"github.com/spf13/afero"
+
+	"github.com/gohugoio/hugo/hugofs"
+
+	"github.com/bep/godartsass"
+)
+
+// See https://github.com/sass/dart-sass-embedded/issues/24
+const stdinPlaceholder = "HUGOSTDIN"
+
+// Supports returns whether dart-sass-embedded is found in $PATH.
+func Supports() bool {
+	if htesting.SupportsAll() {
+		return true
+	}
+	p, err := safeexec.LookPath("dart-sass-embedded")
+	return err == nil && p != ""
+}
+
+type transform struct {
+	optsm map[string]interface{}
+	c     *Client
+}
+
+func (t *transform) Key() internal.ResourceTransformationKey {
+	return internal.NewResourceTransformationKey(transformationName, t.optsm)
+}
+
+func (t *transform) Transform(ctx *resources.ResourceTransformationCtx) error {
+	ctx.OutMediaType = media.CSSType
+
+	opts, err := decodeOptions(t.optsm)
+	if err != nil {
+		return err
+	}
+
+	if opts.TargetPath != "" {
+		ctx.OutPath = opts.TargetPath
+	} else {
+		ctx.ReplaceOutPathExtension(".css")
+	}
+
+	baseDir := path.Dir(ctx.SourcePath)
+
+	args := godartsass.Args{
+		URL:          stdinPlaceholder,
+		IncludePaths: t.c.sfs.RealDirs(baseDir),
+		ImportResolver: importResolver{
+			baseDir: baseDir,
+			c:       t.c,
+		},
+		EnableSourceMap: opts.EnableSourceMap,
+	}
+
+	// Append any workDir relative include paths
+	for _, ip := range opts.IncludePaths {
+		info, err := t.c.workFs.Stat(filepath.Clean(ip))
+		if err == nil {
+			filename := info.(hugofs.FileMetaInfo).Meta().Filename()
+			args.IncludePaths = append(args.IncludePaths, filename)
+		}
+	}
+
+	if ctx.InMediaType.SubType == media.SASSType.SubType {
+		args.SourceSyntax = godartsass.SourceSyntaxSASS
+	}
+
+	res, err := t.c.toCSS(args, ctx.From)
+	if err != nil {
+		if sassErr, ok := err.(godartsass.SassError); ok {
+			start := sassErr.Span.Start
+			context := strings.TrimSpace(sassErr.Span.Context)
+			filename, _ := urlToFilename(sassErr.Span.Url)
+			if filename == stdinPlaceholder {
+				if ctx.SourcePath == "" {
+					return sassErr
+				}
+				filename = t.c.sfs.RealFilename(ctx.SourcePath)
+			}
+
+			offsetMatcher := func(m herrors.LineMatcher) bool {
+				return m.Offset+len(m.Line) >= start.Offset && strings.Contains(m.Line, context)
+			}
+
+			ferr, ok := herrors.WithFileContextForFile(
+				herrors.NewFileError("scss", -1, -1, start.Column, sassErr),
+				filename,
+				filename,
+				hugofs.Os,
+				offsetMatcher)
+
+			if !ok {
+				return sassErr
+			}
+
+			return ferr
+		}
+		return err
+	}
+
+	out := res.CSS
+
+	_, err = io.WriteString(ctx.To, out)
+	if err != nil {
+		return err
+	}
+
+	if opts.EnableSourceMap && res.SourceMap != "" {
+		if err := ctx.PublishSourceMap(res.SourceMap); err != nil {
+			return err
+		}
+		_, err = fmt.Fprintf(ctx.To, "\n\n/*# sourceMappingURL=%s */", path.Base(ctx.OutPath)+".map")
+	}
+
+	return err
+}
+
+type importResolver struct {
+	baseDir string
+	c       *Client
+}
+
+func (t importResolver) CanonicalizeURL(url string) (string, error) {
+	filePath, isURL := urlToFilename(url)
+	var prevDir string
+	var pathDir string
+	if isURL {
+		var found bool
+		prevDir, found = t.c.sfs.MakePathRelative(filepath.Dir(filePath))
+
+		if !found {
+			// Not a member of this filesystem, let Dart Sass handle it.
+			return "", nil
+		}
+	} else {
+		prevDir = t.baseDir
+		pathDir = path.Dir(url)
+	}
+
+	basePath := filepath.Join(prevDir, pathDir)
+	name := filepath.Base(filePath)
+
+	// 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 fim, ok := fi.(hugofs.FileMetaInfo); ok {
+				return "file://" + filepath.ToSlash(fim.Meta().Filename()), nil
+			}
+		}
+	}
+
+	// Not found, let Dart Dass handle it
+	return "", nil
+}
+
+func (t importResolver) Load(url string) (string, error) {
+	filename, _ := urlToFilename(url)
+	b, err := afero.ReadFile(hugofs.Os, filename)
+	return string(b), err
+}
+
+// TODO(bep) add tests
+func urlToFilename(urls string) (string, bool) {
+	u, err := url.ParseRequestURI(urls)
+	if err != nil {
+		return filepath.FromSlash(urls), false
+	}
+	p := filepath.FromSlash(u.Path)
+
+	if u.Host != "" {
+		// C:\data\file.txt
+		p = strings.ToUpper(u.Host) + ":" + p
+	}
+
+	return p, true
+}