mime: text charset defaults

Enforce + document the UTF-8 default.

R=rsc, bradfitz, adg
CC=golang-dev
https://golang.org/cl/4627049

src/pkg/mime/type.go

@@ -7,6 +7,7 @@ package mime
 
 import (
 	"bufio"
+	"fmt"
 	"os"
 	"strings"
 	"sync"
@@ -19,15 +20,15 @@ var typeFiles = []string{
 }
 
 var mimeTypes = map[string]string{
-	".css":  "text/css; charset=utf-8",
+	".css":  "text/css;charset=utf-8",
 	".gif":  "image/gif",
-	".htm":  "text/html; charset=utf-8",
-	".html": "text/html; charset=utf-8",
+	".htm":  "text/html;charset=utf-8",
+	".html": "text/html;charset=utf-8",
 	".jpg":  "image/jpeg",
 	".js":   "application/x-javascript",
 	".pdf":  "application/pdf",
 	".png":  "image/png",
-	".xml":  "text/xml; charset=utf-8",
+	".xml":  "text/xml;charset=utf-8",
 }
 
 var mimeLock sync.RWMutex
@@ -49,15 +50,12 @@ func loadMimeFile(filename string) {
 		if len(fields) <= 1 || fields[0][0] == '#' {
 			continue
 		}
-		typename := fields[0]
-		if strings.HasPrefix(typename, "text/") {
-			typename += "; charset=utf-8"
-		}
+		mimeType := fields[0]
 		for _, ext := range fields[1:] {
 			if ext[0] == '#' {
 				break
 			}
-			mimeTypes["."+ext] = typename
+			setExtensionType("."+ext, mimeType)
 		}
 	}
 }
@@ -81,6 +79,8 @@ var once sync.Once
 //   /etc/mime.types
 //   /etc/apache2/mime.types
 //   /etc/apache/mime.types
+//
+// Text types have the charset parameter set to "utf-8" by default.
 func TypeByExtension(ext string) string {
 	once.Do(initMime)
 	mimeLock.RLock()
@@ -93,12 +93,31 @@ func TypeByExtension(ext string) string {
 // the extension ext to typ.  The extension should begin with
 // a leading dot, as in ".html".
 func AddExtensionType(ext, typ string) os.Error {
-	once.Do(initMime)
-	if len(ext) < 1 || ext[0] != '.' {
-		return os.EINVAL
+	if ext == "" || ext[0] != '.' {
+		return fmt.Errorf(`mime: extension "%s" misses dot`, ext)
 	}
+	once.Do(initMime)
+	return setExtensionType(ext, typ)
+}
+
+func setExtensionType(extension, mimeType string) os.Error {
+	full, param, err := ParseMediaType(mimeType)
+	if err != nil {
+		return err
+	}
+	if split := strings.Index(full, "/"); split < 0 {
+		return fmt.Errorf(`mime: malformed MIME type "%s"`, mimeType)
+	} else {
+		main := full[:split]
+		sub := full[split+1:]
+		if main == "text" && param["charset"] == "" {
+			param["charset"] = "utf-8"
+		}
+		mimeType = FormatMediaType(main, sub, param)
+	}
+
 	mimeLock.Lock()
-	mimeTypes[ext] = typ
+	mimeTypes[extension] = mimeType
 	mimeLock.Unlock()
 	return nil
 }

src/pkg/mime/type_test.go

@@ -2,19 +2,17 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Tests for type.go
-
 package mime
 
 import "testing"
 
 var typeTests = map[string]string{
 	".t1":  "application/test",
-	".t2":  "text/test; charset=utf-8",
+	".t2":  "text/test;charset=utf-8",
 	".png": "image/png",
 }
 
-func TestType(t *testing.T) {
+func TestTypeByExtension(t *testing.T) {
 	typeFiles = []string{"test.types"}
 
 	for ext, want := range typeTests {
@@ -25,3 +23,13 @@ func TestType(t *testing.T) {
 
 	}
 }
+
+func TestCustomExtension(t *testing.T) {
+	custom := "text/xml;charset=iso-8859-1"
+	if error := AddExtensionType(".xml", custom); error != nil {
+		t.Fatalf("error %s for AddExtension(%s)", error, custom)
+	}
+	if registered := TypeByExtension(".xml"); registered != custom {
+		t.Fatalf("registered %s instead of %s", registered, custom)
+	}
+}