fix #215: allow multiple dots in loader extensions

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+* Allow multiple `.` characters in loader extensions ([#215](https://github.com/evanw/esbuild/issues/215))
+
+    You are now able to configure two loaders such that one is the suffix of the other. For example, you can now configure both `--loader:.txt=text` and `--loader:.base64.txt=base64`. The loader with the longer matching suffix will be used.
+
 ## 0.5.19
 
 * Fix bug with TypeScript `typeof` operator ([#213](https://github.com/evanw/esbuild/issues/213))

internal/bundler/bundler.go

@@ -115,11 +115,8 @@ func parseFile(args parseArgs) {
 		args.options.Strict.ClassFields = true
 	}
 
-	// Get the file extension
-	extension := args.fs.Ext(args.absPath)
-
 	// Pick the loader based on the file extension
-	loader := args.options.ExtensionToLoader[extension]
+	loader := loaderFromFileExtension(args.options.ExtensionToLoader, args.fs.Base(args.absPath))
 
 	// Special-case reading from stdin
 	if stdin != nil {
@@ -169,7 +166,7 @@ func parseFile(args parseArgs) {
 		result.file.ignoreIfUnused = true
 
 	case config.LoaderDataURL:
-		mimeType := mime.TypeByExtension(extension)
+		mimeType := mime.TypeByExtension(args.fs.Ext(args.absPath))
 		if mimeType == "" {
 			mimeType = http.DetectContentType([]byte(source.Contents))
 		}
@@ -220,6 +217,23 @@ func parseFile(args parseArgs) {
 	args.results <- result
 }
 
+func loaderFromFileExtension(extensionToLoader map[string]config.Loader, base string) config.Loader {
+	// Pick the loader with the longest matching extension. So if there's an
+	// extension for ".css" and for ".module.css", we want to match the one for
+	// ".module.css" before the one for ".css".
+	for {
+		i := strings.IndexByte(base, '.')
+		if i == -1 {
+			break
+		}
+		if loader, ok := extensionToLoader[base[i:]]; ok {
+			return loader
+		}
+		base = base[i+1:]
+	}
+	return config.LoaderNone
+}
+
 // Identify the path by its lowercase absolute path name. This should
 // hopefully avoid path case issues on Windows, which has case-insensitive
 // file system paths.

internal/bundler/bundler_test.go

@@ -2689,6 +2689,43 @@ console.log(require_test());
 	})
 }
 
+func TestRequireCustomExtensionPreferLongest(t *testing.T) {
+	expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.js": `
+				console.log(require('./test.txt'), require('./test.base64.txt'))
+			`,
+			"/test.txt":        `test.txt`,
+			"/test.base64.txt": `test.base64.txt`,
+		},
+		entryPaths: []string{"/entry.js"},
+		options: config.Options{
+			IsBundling:    true,
+			AbsOutputFile: "/out.js",
+			ExtensionToLoader: map[string]config.Loader{
+				".js":         config.LoaderJS,
+				".txt":        config.LoaderText,
+				".base64.txt": config.LoaderBase64,
+			},
+		},
+		expected: map[string]string{
+			"/out.js": `// /test.txt
+var require_test = __commonJS((exports, module) => {
+  module.exports = "test.txt";
+});
+
+// /test.base64.txt
+var require_test_base64 = __commonJS((exports, module) => {
+  module.exports = "dGVzdC5iYXNlNjQudHh0";
+});
+
+// /entry.js
+console.log(require_test(), require_test_base64());
+`,
+		},
+	})
+}
+
 func testAutoDetectMimeTypeFromExtension(t *testing.T) {
 	expectBundled(t, bundled{
 		files: map[string]string{

pkg/api/api_impl.go

@@ -161,7 +161,7 @@ func validateLoaders(log logging.Log, loaders map[string]Loader) map[string]conf
 	result := bundler.DefaultExtensionToLoaderMap()
 	if loaders != nil {
 		for ext, loader := range loaders {
-			if len(ext) < 2 || ext[0] != '.' || strings.ContainsRune(ext[1:], '.') {
+			if len(ext) < 2 || ext[0] != '.' || ext[len(ext)-1] == '.' {
 				log.AddError(nil, ast.Loc{}, fmt.Sprintf("Invalid file extension: %q", ext))
 			}
 			result[ext] = validateLoader(loader)