dartsass: Enable deprecation, @warn and @debug logging

* @warn and Sass deprecations are printed as WARN
* @debug is currently logged as INFO (needs the `--verbose` flag). We may adjust this if it gets too chatty.

Fixes #9683

resources/resource_transformers/tocss/dartsass/client.go

@@ -18,6 +18,7 @@ package dartsass
 import (
 	"fmt"
 	"io"
+	"strings"
 
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/gohugoio/hugo/hugolib/filesystems"
@@ -41,7 +42,19 @@ func New(fs *filesystems.SourceFilesystem, rs *resources.Spec) (*Client, error)
 		return nil, err
 	}
 
-	transpiler, err := godartsass.Start(godartsass.Options{})
+	transpiler, err := godartsass.Start(godartsass.Options{
+		LogEventHandler: func(event godartsass.LogEvent) {
+			message := strings.ReplaceAll(event.Message, stdinPrefix, "")
+			switch event.Type {
+			case godartsass.LogEventTypeDebug:
+				// Log as Info for now, we may adjust this if it gets too chatty.
+				rs.Logger.Infof("Dart Sass: %s", message)
+			default:
+				// The rest are either deprecations or @warn statements.
+				rs.Logger.Warnf("Dart Sass: %s", message)
+			}
+		},
+	})
 	if err != nil {
 		return nil, err
 	}

resources/resource_transformers/tocss/dartsass/integration_test.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/gohugoio/hugo/hugolib"
 	"github.com/gohugoio/hugo/resources/resource_transformers/tocss/dartsass"
+	jww "github.com/spf13/jwalterweatherman"
 )
 
 func TestTransformIncludePaths(t *testing.T) {
@@ -164,3 +165,34 @@ zoo {
 
 	b.AssertFileContent("public/index.html", `T1: moo{color:#ccc}boo{color:green}zoo{color:pink}`)
 }
+
+func TestTransformLogging(t *testing.T) {
+	if !dartsass.Supports() {
+		t.Skip()
+	}
+
+	files := `
+-- assets/scss/main.scss --
+@warn "foo";
+@debug "bar";
+
+-- config.toml --
+disableKinds = ["term", "taxonomy", "section", "page"]
+-- layouts/index.html --
+{{ $cssOpts := (dict  "transpiler" "dartsass" ) }}
+{{ $r := resources.Get "scss/main.scss" |  toCSS $cssOpts   }}
+T1: {{ $r.Content }}
+	`
+
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+			NeedsOsFS:   true,
+			LogLevel:    jww.LevelInfo,
+		}).Build()
+
+	b.AssertLogMatches(`WARN.*Dart Sass: foo`)
+	b.AssertLogMatches(`INFO.*Dart Sass: .*assets.*main.scss:1:0: bar`)
+
+}

resources/resource_transformers/tocss/dartsass/transform.go

@@ -39,7 +39,8 @@ import (
 
 const (
 	// See https://github.com/sass/dart-sass-embedded/issues/24
-	stdinPlaceholder           = "HUGOSTDIN"
+	// Note: This prefix must be all lower case.
+	stdinPrefix                = "hugostdin:"
 	dartSassEmbeddedBinaryName = "dart-sass-embedded"
 )
 
@@ -75,9 +76,14 @@ func (t *transform) Transform(ctx *resources.ResourceTransformationCtx) error {
 	}
 
 	baseDir := path.Dir(ctx.SourcePath)
+	filename := stdinPrefix
+
+	if ctx.SourcePath != "" {
+		filename += t.c.sfs.RealFilename(ctx.SourcePath)
+	}
 
 	args := godartsass.Args{
-		URL:          stdinPlaceholder,
+		URL:          filename,
 		IncludePaths: t.c.sfs.RealDirs(baseDir),
 		ImportResolver: importResolver{
 			baseDir: baseDir,
@@ -106,11 +112,8 @@ func (t *transform) Transform(ctx *resources.ResourceTransformationCtx) error {
 			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)
+			if strings.HasPrefix(filename, stdinPrefix) {
+				filename = filename[len(stdinPrefix):]
 			}
 
 			offsetMatcher := func(m herrors.LineMatcher) bool {