Fix indented SASS imports for Dart Sass

Fixes #11074

resources/resource_transformers/tocss/dartsass/integration_test.go

@@ -109,6 +109,38 @@ T1: {{ $r.Content | safeHTML }}
 		/* foo */`)
 }
 
+func TestTransformImportIndentedSASS(t *testing.T) {
+	t.Parallel()
+	if !dartsass.Supports() {
+		t.Skip()
+	}
+
+	files := `
+-- assets/scss/_moo.sass --
+#main
+	color: blue
+-- assets/scss/main.scss --
+@import "moo";
+
+/* foo */
+-- config.toml --
+-- layouts/index.html --
+{{ $r := resources.Get "scss/main.scss" |  toCSS (dict "transpiler" "dartsass")  }}
+T1: {{ $r.Content | safeHTML }}
+
+	`
+
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+			NeedsOsFS:   true,
+		},
+	).Build()
+
+	b.AssertFileContent("public/index.html", "T1: #main {\n  color: blue;\n}\n\n/* foo */")
+}
+
 // Issue 10592
 func TestTransformImportMountedCSS(t *testing.T) {
 	t.Parallel()

resources/resource_transformers/tocss/dartsass/transform.go

@@ -86,7 +86,7 @@ func (t *transform) Transform(ctx *resources.ResourceTransformationCtx) error {
 			baseDir: baseDir,
 			c:       t.c,
 
-			varsStylesheet: sass.CreateVarsStyleSheet(opts.Vars),
+			varsStylesheet: godartsass.Import{Content: sass.CreateVarsStyleSheet(opts.Vars)},
 		},
 		OutputStyle:             godartsass.ParseOutputStyle(opts.OutputStyle),
 		EnableSourceMap:         opts.EnableSourceMap,
@@ -132,7 +132,7 @@ type importResolver struct {
 	baseDir string
 	c       *Client
 
-	varsStylesheet string
+	varsStylesheet godartsass.Import
 }
 
 func (t importResolver) CanonicalizeURL(url string) (string, error) {
@@ -184,11 +184,20 @@ func (t importResolver) CanonicalizeURL(url string) (string, error) {
 	return "", nil
 }
 
-func (t importResolver) Load(url string) (string, error) {
+func (t importResolver) Load(url string) (godartsass.Import, error) {
 	if url == sass.HugoVarsNamespace {
 		return t.varsStylesheet, nil
 	}
 	filename, _ := paths.UrlToFilename(url)
 	b, err := afero.ReadFile(hugofs.Os, filename)
-	return string(b), err
+
+	sourceSyntax := godartsass.SourceSyntaxSCSS
+	if strings.HasSuffix(filename, ".sass") {
+		sourceSyntax = godartsass.SourceSyntaxSASS
+	} else if strings.HasSuffix(filename, ".css") {
+		sourceSyntax = godartsass.SourceSyntaxCSS
+	}
+
+	return godartsass.Import{Content: string(b), SourceSyntax: sourceSyntax}, err
+
 }