mime: tighten up and simplify tests

Don't test so much at once.

Fixes #10278

Change-Id: I32a9cb81a3cffecc7ce4f83c35a4b589bcd3a9f7
Reviewed-on: https://go-review.googlesource.com/8213
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/mime/type.go

@@ -12,8 +12,27 @@ import (
 )
 
 var (
-	mimeLock       sync.RWMutex
-	mimeTypesLower = map[string]string{
+	mimeLock       sync.RWMutex      // guards following 3 maps
+	mimeTypes      map[string]string // ".Z" => "application/x-compress"
+	mimeTypesLower map[string]string // ".z" => "application/x-compress"
+
+	// extensions maps from MIME type to list of lowercase file
+	// extensions: "image/jpeg" => [".jpg", ".jpeg"]
+	extensions map[string][]string
+)
+
+// setMimeTypes is used by initMime's non-test path, and by tests.
+// The two maps must not be the same, or nil.
+func setMimeTypes(lowerExt, mixExt map[string]string) {
+	if lowerExt == nil || mixExt == nil {
+		panic("nil map")
+	}
+	mimeTypesLower = lowerExt
+	mimeTypes = mixExt
+	extensions = invert(lowerExt)
+}
+
+var builtinTypesLower = map[string]string{
 	".css":  "text/css; charset=utf-8",
 	".gif":  "image/gif",
 	".htm":  "text/html; charset=utf-8",
@@ -24,17 +43,14 @@ var (
 	".png":  "image/png",
 	".svg":  "image/svg+xml",
 	".xml":  "text/xml; charset=utf-8",
-	}
-	mimeTypes  = clone(mimeTypesLower)
-	extensions = invert(mimeTypesLower)
-)
+}
 
 func clone(m map[string]string) map[string]string {
 	m2 := make(map[string]string, len(m))
 	for k, v := range m {
 		m2[k] = v
 		if strings.ToLower(k) != k {
-			panic("keys in mimeTypesLower must be lowercase")
+			panic("keys in builtinTypesLower must be lowercase")
 		}
 	}
 	return m2
@@ -54,6 +70,17 @@ func invert(m map[string]string) map[string][]string {
 
 var once sync.Once // guards initMime
 
+var testInitMime, osInitMime func()
+
+func initMime() {
+	if fn := testInitMime; fn != nil {
+		fn()
+	} else {
+		setMimeTypes(builtinTypesLower, clone(builtinTypesLower))
+		osInitMime()
+	}
+}
+
 // TypeByExtension returns the MIME type associated with the file extension ext.
 // The extension ext should begin with a leading dot, as in ".html".
 // When ext has no associated type, TypeByExtension returns "".
@@ -77,8 +104,7 @@ func TypeByExtension(ext string) string {
 	defer mimeLock.RUnlock()
 
 	// Case-sensitive lookup.
-	v := mimeTypes[ext]
-	if v != "" {
+	if v := mimeTypes[ext]; v != "" {
 		return v
 	}
 
@@ -130,7 +156,7 @@ func ExtensionsByType(typ string) ([]string, error) {
 // a leading dot, as in ".html".
 func AddExtensionType(ext, typ string) error {
 	if !strings.HasPrefix(ext, ".") {
-		return fmt.Errorf(`mime: extension %q misses dot`, ext)
+		return fmt.Errorf("mime: extension %q missing leading dot", ext)
 	}
 	once.Do(initMime)
 	return setExtensionType(ext, typ)

src/mime/type_plan9.go

@@ -10,10 +10,29 @@ import (
 	"strings"
 )
 
+func init() {
+	osInitMime = initMimePlan9
+}
+
+func initMimePlan9() {
+	for _, filename := range typeFiles {
+		loadMimeFile(filename)
+	}
+}
+
 var typeFiles = []string{
 	"/sys/lib/mimetypes",
 }
 
+func initMimeForTests() map[string]string {
+	typeFiles = []string{"testdata/test.types.plan9"}
+	return map[string]string{
+		".t1":  "application/test",
+		".t2":  "text/test; charset=utf-8",
+		".pNg": "image/png",
+	}
+}
+
 func loadMimeFile(filename string) {
 	f, err := os.Open(filename)
 	if err != nil {
@@ -36,18 +55,3 @@ func loadMimeFile(filename string) {
 		panic(err)
 	}
 }
-
-func initMime() {
-	for _, filename := range typeFiles {
-		loadMimeFile(filename)
-	}
-}
-
-func initMimeForTests() map[string]string {
-	typeFiles = []string{"testdata/test.types.plan9"}
-	return map[string]string{
-		".t1":  "application/test",
-		".t2":  "text/test; charset=utf-8",
-		".pNg": "image/png",
-	}
-}

src/mime/type_test.go

@@ -6,14 +6,40 @@ package mime
 
 import (
 	"reflect"
-	"sort"
 	"strings"
+	"sync"
 	"testing"
 )
 
-var typeTests = initMimeForTests()
+func setMimeInit(fn func()) (cleanup func()) {
+	once = sync.Once{}
+	testInitMime = fn
+	return func() { testInitMime = nil }
+}
+
+func clearMimeTypes() {
+	setMimeTypes(map[string]string{}, map[string]string{})
+}
+
+func setType(ext, typ string) {
+	if !strings.HasPrefix(ext, ".") {
+		panic("missing leading dot")
+	}
+	if err := setExtensionType(ext, typ); err != nil {
+		panic("bad test data: " + err.Error())
+	}
+}
 
 func TestTypeByExtension(t *testing.T) {
+	once = sync.Once{}
+	// initMimeForTests returns the platform-specific extension =>
+	// type tests. On Unix and Plan 9, this also tests the parsing
+	// of MIME text files (in testdata/*). On Windows, we test the
+	// real registry on the machine and assume that ".png" exists
+	// there, which empirically it always has, for all versions of
+	// Windows.
+	typeTests := initMimeForTests()
+
 	for ext, want := range typeTests {
 		val := TypeByExtension(ext)
 		if val != want {
@@ -22,15 +48,41 @@ func TestTypeByExtension(t *testing.T) {
 	}
 }
 
+func TestTypeByExtension_LocalData(t *testing.T) {
+	cleanup := setMimeInit(func() {
+		clearMimeTypes()
+		setType(".foo", "x/foo")
+		setType(".bar", "x/bar")
+		setType(".Bar", "x/bar; capital=1")
+	})
+	defer cleanup()
+
+	tests := map[string]string{
+		".foo":          "x/foo",
+		".bar":          "x/bar",
+		".Bar":          "x/bar; capital=1",
+		".sdlkfjskdlfj": "",
+		".t1":           "", // testdata shouldn't be used
+	}
+
+	for ext, want := range tests {
+		val := TypeByExtension(ext)
+		if val != want {
+			t.Errorf("TypeByExtension(%q) = %q, want %q", ext, val, want)
+		}
+	}
+}
+
 func TestTypeByExtensionCase(t *testing.T) {
 	const custom = "test/test; charset=iso-8859-1"
 	const caps = "test/test; WAS=ALLCAPS"
-	if err := AddExtensionType(".TEST", caps); err != nil {
-		t.Fatalf("error %s for AddExtension(%s)", err, custom)
-	}
-	if err := AddExtensionType(".tesT", custom); err != nil {
-		t.Fatalf("error %s for AddExtension(%s)", err, custom)
-	}
+
+	cleanup := setMimeInit(func() {
+		clearMimeTypes()
+		setType(".TEST", caps)
+		setType(".tesT", custom)
+	})
+	defer cleanup()
 
 	// case-sensitive lookup
 	if got := TypeByExtension(".tesT"); got != custom {
@@ -47,55 +99,43 @@ func TestTypeByExtensionCase(t *testing.T) {
 }
 
 func TestExtensionsByType(t *testing.T) {
-	for want, typ := range typeTests {
-		val, err := ExtensionsByType(typ)
-		if err != nil {
-			t.Errorf("error %s for ExtensionsByType(%q)", err, typ)
+	cleanup := setMimeInit(func() {
+		clearMimeTypes()
+		setType(".gif", "image/gif")
+		setType(".a", "foo/letter")
+		setType(".b", "foo/letter")
+		setType(".B", "foo/letter")
+		setType(".PNG", "image/png")
+	})
+	defer cleanup()
+
+	tests := []struct {
+		typ     string
+		want    []string
+		wantErr string
+	}{
+		{typ: "image/gif", want: []string{".gif"}},
+		{typ: "image/png", want: []string{".png"}}, // lowercase
+		{typ: "foo/letter", want: []string{".a", ".b"}},
+		{typ: "x/unknown", want: nil},
+	}
+
+	for _, tt := range tests {
+		got, err := ExtensionsByType(tt.typ)
+		if err != nil && tt.wantErr != "" && strings.Contains(err.Error(), tt.wantErr) {
 			continue
 		}
-		if len(val) != 1 {
-			t.Errorf("ExtensionsByType(%q) = %v; expected exactly 1 entry", typ, val)
+		if err != nil {
+			t.Errorf("ExtensionsByType(%q) error: %v", tt.typ, err)
 			continue
 		}
-		// We always expect lower case, test data includes upper-case.
-		want = strings.ToLower(want)
-		if val[0] != want {
-			t.Errorf("ExtensionsByType(%q) = %q, want %q", typ, val[0], want)
+		if tt.wantErr != "" {
+			t.Errorf("ExtensionsByType(%q) = %q, %v; want error substring %q", tt.typ, got, err, tt.wantErr)
+			continue
 		}
+		if !reflect.DeepEqual(got, tt.want) {
+			t.Errorf("ExtensionsByType(%q) = %q; want %q", tt.typ, got, tt.want)
 		}
-}
-
-func TestExtensionsByTypeMultiple(t *testing.T) {
-	const typ = "text/html"
-	exts, err := ExtensionsByType(typ)
-	if err != nil {
-		t.Fatalf("ExtensionsByType(%q) error: %v", typ, err)
-	}
-	sort.Strings(exts)
-	if want := []string{".htm", ".html"}; !reflect.DeepEqual(exts, want) {
-		t.Errorf("ExtensionsByType(%q) = %v; want %v", typ, exts, want)
-	}
-}
-
-func TestExtensionsByTypeNoDuplicates(t *testing.T) {
-	const (
-		typ = "text/html"
-		ext = ".html"
-	)
-	AddExtensionType(ext, typ)
-	AddExtensionType(ext, typ)
-	exts, err := ExtensionsByType(typ)
-	if err != nil {
-		t.Fatalf("ExtensionsByType(%q) error: %v", typ, err)
-	}
-	count := 0
-	for _, v := range exts {
-		if v == ext {
-			count++
-		}
-	}
-	if count != 1 {
-		t.Errorf("ExtensionsByType(%q) = %v; want %v once", typ, exts, ext)
 	}
 }
 

src/mime/type_unix.go

@@ -12,6 +12,10 @@ import (
 	"strings"
 )
 
+func init() {
+	osInitMime = initMimeUnix
+}
+
 var typeFiles = []string{
 	"/etc/mime.types",
 	"/etc/apache2/mime.types",
@@ -44,7 +48,7 @@ func loadMimeFile(filename string) {
 	}
 }
 
-func initMime() {
+func initMimeUnix() {
 	for _, filename := range typeFiles {
 		loadMimeFile(filename)
 	}

src/mime/type_windows.go

@@ -9,7 +9,11 @@ import (
 	"unsafe"
 )
 
-func initMime() {
+func init() {
+	osInitMime = initMimeWindows
+}
+
+func initMimeWindows() {
 	var root syscall.Handle
 	rootpathp, _ := syscall.UTF16PtrFromString(`\`)
 	if syscall.RegOpenKeyEx(syscall.HKEY_CLASSES_ROOT, rootpathp,
@@ -21,6 +25,7 @@ func initMime() {
 	if syscall.RegQueryInfoKey(root, nil, nil, nil, &count, nil, nil, nil, nil, nil, nil, nil) != nil {
 		return
 	}
+	contenttypep, _ := syscall.UTF16PtrFromString("Content Type")
 	var buf [1 << 10]uint16
 	for i := uint32(0); i < count; i++ {
 		n := uint32(len(buf))
@@ -40,7 +45,6 @@ func initMime() {
 		}
 		var typ uint32
 		n = uint32(len(buf) * 2) // api expects array of bytes, not uint16
-		contenttypep, _ := syscall.UTF16PtrFromString("Content Type")
 		if syscall.RegQueryValueEx(
 			h, contenttypep,
 			nil, &typ, (*byte)(unsafe.Pointer(&buf[0])), &n) != nil {