tpl/css: Fix external source maps

Fixes #14620

internal/js/esbuild/build.go

@@ -225,7 +225,12 @@ func (c *BuildClient) Build(opts Options) (api.BuildResult, error) {
 					}
 					return ss
 				}
-				return ""
+				if strings.HasPrefix(s, opts.OutDir) {
+					// This is an output file, not a source file.
+					return ""
+				}
+				// s is already the absolute filename set by the Hugo resolve plugin.
+				return s
 			}
 			return s
 		}); err != nil {

internal/js/esbuild/sourcemap.go

@@ -46,7 +46,27 @@ func fixSourceMap(s []byte, resolve func(string) string) ([]byte, error) {
 		return nil, err
 	}
 
-	sm.Sources = fixSourceMapSources(sm.Sources, resolve)
+	hasSourcesContent := len(sm.SourcesContent) == len(sm.Sources)
+
+	var sources []string
+	var sourcesContent []string
+	for i, src := range sm.Sources {
+		if resolved := resolve(src); resolved != "" {
+			// Absolute filenames works fine on U*ix (tested in Chrome on MacOs), but works very poorly on Windows (again Chrome).
+			// So, convert it to a URL.
+			if u, err := paths.UrlFromFilename(resolved); err == nil {
+				sources = append(sources, u.String())
+				if hasSourcesContent {
+					sourcesContent = append(sourcesContent, sm.SourcesContent[i])
+				}
+			}
+		}
+	}
+
+	sm.Sources = sources
+	if hasSourcesContent {
+		sm.SourcesContent = sourcesContent
+	}
 
 	b, err := json.Marshal(sm)
 	if err != nil {
@@ -56,20 +76,6 @@ func fixSourceMap(s []byte, resolve func(string) string) ([]byte, error) {
 	return b, nil
 }
 
-func fixSourceMapSources(s []string, resolve func(string) string) []string {
-	var result []string
-	for _, src := range s {
-		if s := resolve(src); s != "" {
-			// Absolute filenames works fine on U*ix (tested in Chrome on MacOs), but works very poorly on Windows (again Chrome).
-			// So, convert it to a URL.
-			if u, err := paths.UrlFromFilename(s); err == nil {
-				result = append(result, u.String())
-			}
-		}
-	}
-	return result
-}
-
 // Used in tests.
 func SourcesFromSourceMap(s string) []string {
 	var sm sourceMap

resources/resource_transformers/js/js_integration_test.go

@@ -228,7 +228,7 @@ TS2: {{ template "print" $ts2 }}
 		}
 	}
 
-	checkMap("public/js/main.js.map", 4)
+	checkMap("public/js/main.js.map", 5)
 }
 
 func TestBuildError(t *testing.T) {

tpl/css/build_integration_test.go

@@ -17,8 +17,10 @@ import (
 	"strings"
 	"testing"
 
+	qt "github.com/frankban/quicktest"
 	"github.com/gohugoio/hugo/htesting"
 	"github.com/gohugoio/hugo/hugolib"
+	"github.com/gohugoio/hugo/internal/js/esbuild"
 )
 
 func TestCSSBuild(t *testing.T) {
@@ -165,30 +167,45 @@ span { background: green; }
 article { background: yellow; }
 -- layouts/home.html --
 {{ with resources.Get "css/main.css"  }}
-{{ $opts := (dict "minify" false "sourceMap" "SOURCE_MAP" "sourcesContent" SOURCES_CONTENT  "loaders" (dict ".png" "dataurl"))}}
+{{ $opts := (dict "minify" MINIFY "sourceMap" "SOURCE_MAP" "sourcesContent" SOURCES_CONTENT  "loaders" (dict ".png" "dataurl"))}}
 {{ with . | css.Build $opts  }}
  <link rel="stylesheet" href="{{ .RelPermalink }}" />
 {{ end }}
 {{ end }}
 	`
 
-	r := strings.NewReplacer(
-		"SOURCE_MAP", "linked",
-		"SOURCES_CONTENT", "true",
+	var (
+		r     *strings.Replacer
+		files string
+		b     *hugolib.IntegrationTestBuilder
 	)
 
-	files := r.Replace(filesTemplate)
+	for _, minify := range []string{"true", "false"} {
 
-	b := hugolib.Test(t, files, hugolib.TestOptOsFs())
-	b.AssertFileContent("public/css/main.css", "/*# sourceMappingURL=main.css.map */")
-	b.AssertFileContent("public/css/main.css.map",
-		`"sourcesContent":["p { background: red; }"`,
-		"AAAA;AAAI,cAAY;AAAK",
-	)
+		r = strings.NewReplacer(
+			"SOURCE_MAP", "linked",
+			"SOURCES_CONTENT", "true",
+			"MINIFY", minify,
+		)
+
+		files = r.Replace(filesTemplate)
+
+		b = hugolib.Test(t, files, hugolib.TestOptOsFs())
+		b.AssertFileContent("public/css/main.css", "/*# sourceMappingURL=main.css.map */")
+		b.AssertFileContent("public/css/main.css.map",
+			`"sourcesContent":["`,
+			`"mappings":"`,
+		)
+
+		sources := esbuild.SourcesFromSourceMap(b.FileContent("public/css/main.css.map"))
+		// main.css + foo.css + bar.css + baz.css = 4 sources.
+		b.Assert(len(sources), qt.Equals, 4)
+	}
 
 	r = strings.NewReplacer(
 		"SOURCE_MAP", "external",
 		"SOURCES_CONTENT", "true",
+		"MINIFY", "false",
 	)
 
 	files = r.Replace(filesTemplate)
@@ -203,6 +220,7 @@ article { background: yellow; }
 	r = strings.NewReplacer(
 		"SOURCE_MAP", "external",
 		"SOURCES_CONTENT", "false",
+		"MINIFY", "false",
 	)
 
 	files = r.Replace(filesTemplate)
@@ -216,6 +234,7 @@ article { background: yellow; }
 	r = strings.NewReplacer(
 		"SOURCE_MAP", "inline",
 		"SOURCES_CONTENT", "false",
+		"MINIFY", "false",
 	)
 
 	files = r.Replace(filesTemplate)