Remove charset restrictions on tag values

See: census-instrumentation/opencensus-specs#71

tag/doc.go

@@ -22,5 +22,12 @@ the OpenCensus instrumentation data.
 Tags can be propagated on the wire and in the same
 process via context.Context. Encode and Decode should be
 used to represent tags into their binary propagation form.
+
+This package supports a restrictive set of characters in tag keys which
+we believe are supported by most metrics backends. Tag values are not limited in
+this way, but specific exporters may have their own restrictions on tag
+values and if so, should provide a way to sanitize tag values for use
+with that backend.
+
 */
 package tag // import "go.opencensus.io/tag"

tag/map_codec_test.go

@@ -67,7 +67,7 @@ func TestEncodeDecode(t *testing.T) {
 			[]keyValue{
 				{k1, "v1"},
 				{k2, "v2"},
-				{k3, "v3"},
+				{k3, "数据库着火了 🔥🔥🔥"},
 				{k4, "v4 is very weird <>.,?/'\";:`~!@#$%^&*()_-+={[}]|\\"},
 			},
 		},
@@ -107,6 +107,7 @@ func TestEncodeDecode(t *testing.T) {
 func TestDecode(t *testing.T) {
 	k1, _ := NewKey("k1")
 	ctx, _ := New(context.Background(), Insert(k1, "v1"))
+	ctx2, _ := New(context.Background(), Insert(k1, "数据库着火了 🔥🔥🔥"))
 
 	tests := []struct {
 		name    string
@@ -121,14 +122,14 @@ func TestDecode(t *testing.T) {
 			wantErr: false,
 		},
 		{
-			name:    "non-ascii key",
-			bytes:   []byte{0, 0, 2, 107, 49, 2, 118, 49, 0, 2, 107, 25, 2, 118, 49},
-			want:    nil,
-			wantErr: true,
+			name:    "valid (non-ascii value)",
+			bytes:   []byte{0x0, 0x0, 0x2, 0x6b, 0x31, 0x1f, 0xe6, 0x95, 0xb0, 0xe6, 0x8d, 0xae, 0xe5, 0xba, 0x93, 0xe7, 0x9d, 0x80, 0xe7, 0x81, 0xab, 0xe4, 0xba, 0x86, 0x20, 0xf0, 0x9f, 0x94, 0xa5, 0xf0, 0x9f, 0x94, 0xa5, 0xf0, 0x9f, 0x94, 0xa5},
+			want:    FromContext(ctx2),
+			wantErr: false,
 		},
 		{
-			name:    "non-ascii value",
-			bytes:   []byte{0, 0, 2, 107, 49, 2, 118, 49, 0, 2, 107, 50, 2, 118, 25},
+			name:    "non-ascii key",
+			bytes:   []byte{0, 0, 2, 107, 49, 2, 118, 49, 0, 2, 107, 25, 2, 118, 49},
 			want:    nil,
 			wantErr: true,
 		},
@@ -147,7 +148,11 @@ func TestDecode(t *testing.T) {
 				return
 			}
 			if !reflect.DeepEqual(got, tt.want) {
-				t.Errorf("Decode() = %v, want %v", got, tt.want)
+				var encoded []byte
+				if tt.want != nil {
+					encoded = Encode(tt.want)
+				}
+				t.Errorf("Decode() = %v, want %v = Decode(%#v)", got, tt.want, encoded)
 			}
 		})
 	}

tag/validate.go

@@ -26,7 +26,7 @@ const (
 
 var (
 	errInvalidKeyName = errors.New("invalid key name: only ASCII characters accepted; max length must be 255 characters")
-	errInvalidValue   = errors.New("invalid value: only ASCII characters accepted; max length must be 255 characters")
+	errInvalidValue   = errors.New("invalid value: max length must be 255 UTF-8 characters")
 )
 
 func checkKeyName(name string) bool {
@@ -52,5 +52,5 @@ func checkValue(v string) bool {
 	if len(v) > maxKeyLength {
 		return false
 	}
-	return isASCII(v)
+	return true
 }

tag/validate_test.go

@@ -75,16 +75,6 @@ func TestCheckValue(t *testing.T) {
 			value:  "v1",
 			wantOK: true,
 		},
-		{
-			name:   "invalid i",
-			value:  "k\x19",
-			wantOK: false,
-		},
-		{
-			name:   "invalid ii",
-			value:  "k\x7f",
-			wantOK: false,
-		},
 		{
 			name:   "empty",
 			value:  "",
@@ -100,6 +90,21 @@ func TestCheckValue(t *testing.T) {
 			value:  strings.Repeat("a", 256),
 			wantOK: false,
 		},
+		{
+			name:   "emoji",
+			value:  "🔥🔥🔥",
+			wantOK: true,
+		},
+		{
+			name:   "Simplified Chinese",
+			value:  "上海",
+			wantOK: true,
+		},
+		{
+			name:   "Bengali",
+			value:  "বাংলা/বঙ্গ",
+			wantOK: true,
+		},
 	}
 	for _, tt := range tests {
 		ok := checkValue(tt.value)