[assetserver] Add more builtin mimetypes by extension (#2391)

v2/pkg/assetserver/mimecache.go

@@ -9,24 +9,44 @@ import (
 )
 
 var (
-	cache = map[string]string{}
+	mimeCache = map[string]string{}
-	mutex sync.Mutex
+	mimeMutex sync.Mutex
+
+	// The list of builtin mime-types by extension as defined by
+	// the golang standard lib package "mime"
+	// The standard lib also takes into account mime type definitions from
+	// etc files like '/etc/apache2/mime.types' but we want to have the
+	// same behavivour on all platforms and not depend on some external file.
+	mimeTypesByExt = map[string]string{
+		".avif": "image/avif",
+		".css":  "text/css; charset=utf-8",
+		".gif":  "image/gif",
+		".htm":  "text/html; charset=utf-8",
+		".html": "text/html; charset=utf-8",
+		".jpeg": "image/jpeg",
+		".jpg":  "image/jpeg",
+		".js":   "text/javascript; charset=utf-8",
+		".json": "application/json",
+		".mjs":  "text/javascript; charset=utf-8",
+		".pdf":  "application/pdf",
+		".png":  "image/png",
+		".svg":  "image/svg+xml",
+		".wasm": "application/wasm",
+		".webp": "image/webp",
+		".xml":  "text/xml; charset=utf-8",
+	}
 )
 
 func GetMimetype(filename string, data []byte) string {
-	mutex.Lock()
+	mimeMutex.Lock()
-	defer mutex.Unlock()
+	defer mimeMutex.Unlock()
 
-	// short-circuit .js, .css to ensure the
+	result := mimeTypesByExt[filepath.Ext(filename)]
-	// browser evaluates them in the right context
+	if result != "" {
-	switch filepath.Ext(filename) {
+		return result
-	case ".js":
-		return "application/javascript"
-	case ".css":
-		return "text/css; charset=utf-8"
 	}
 
-	result := cache[filename]
+	result = mimeCache[filename]
 	if result != "" {
 		return result
 	}
@@ -42,6 +62,6 @@ func GetMimetype(filename string, data []byte) string {
 		result = "application/octet-stream"
 	}
 
-	cache[filename] = result
+	mimeCache[filename] = result
 	return result
 }

v2/pkg/assetserver/mimecache_test.go

@@ -25,10 +25,11 @@ func TestGetMimetype(t *testing.T) {
 		want string
 	}{
 		// TODO: Add test cases.
-		{"nil data", args{"nil.svg", nil}, "text/plain"},
+		{"nil data", args{"nil.svg", nil}, "image/svg+xml"},
-		{"empty data", args{"empty.html", emptyMsg}, "text/plain"},
+		{"empty data", args{"empty.html", emptyMsg}, "text/html; charset=utf-8"},
 		{"css", args{"test.css", css}, "text/css; charset=utf-8"},
-		{"js", args{"test.js", []byte("let foo = 'bar'; console.log(foo);")}, "application/javascript"},
+		{"js", args{"test.js", []byte("let foo = 'bar'; console.log(foo);")}, "text/javascript; charset=utf-8"},
+		{"mjs", args{"test.mjs", []byte("let foo = 'bar'; console.log(foo);")}, "text/javascript; charset=utf-8"},
 		{"html-utf8", args{"test_utf8.html", html}, "text/html; charset=utf-8"},
 		{"html-bom-utf8", args{"test_bom_utf8.html", bomHtml}, "text/html; charset=utf-8"},
 		{"svg", args{"test.svg", svg}, "image/svg+xml"},

website/src/pages/changelog.mdx

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added Webview GPU acceleration options for [Windows](/docs/reference/options#webviewgpuisdisabled) and [Linux](/docs/reference/options#webviewgpupolicy). Added by @Lyimmi in [PR](https://github.com/wailsapp/wails/pull/2266)
 - Added `EnableFraudulentWebsiteDetection` option to opt-in to scan services for fraudulent content, such as malware or phishing attempts. Older releases had the scan services per default activated. Added by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2269)
 - Allow an [AssetServer Middleware](/docs/reference/options#middleware) to specify the `Content-Type` of a file served by the [Assets](/docs/reference/options#assets-1) `fs.FS`. Added by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2286)
+- The AssetServer now detects more mimetypes by extension, e.g. `.mjs`. Added by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2391)
 
 ### Changed
 - Improved fullscreen mode for frameless window on Windows. Changed by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2279), [PR](https://github.com/wailsapp/wails/pull/2288) and [PR](https://github.com/wailsapp/wails/pull/2299)