MM-41909: Allow 1 char channel name (#19845)

* [ MM-41909 ] Allow 1 character channel names

Change minimal length to 1

* [ MM-41909 ] Fix localization string

* [ MM-41909 ] Modify condition to allow 1 char channel name

* [ MM-41909 ] fix formatting

* [MM-41909] Linting fix

* [MM-41909] Fix regex

* [MM-41909] Localization update

* [MM-41909] Attempt to fix test

Co-authored-by: Kevin Jiang <>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/slashcommands/command_channel_rename_test.go

@@ -28,7 +28,7 @@ func TestRenameProviderDoCommand(t *testing.T) {
 	// Table Test for basic cases. Blank text in response indicates success
 	for msg, expected := range map[string]string{
 		"":                                    "api.command_channel_rename.message.app_error",
-		"o":                                   "api.command_channel_rename.too_short.app_error",
+		"o":                                   "",
 		"joram":                               "",
 		"More than 22 chars but less than 64": "",
 		strings.Repeat("12345", 13):           "api.command_channel_rename.too_long.app_error",

i18n/en.json

@@ -7688,8 +7688,8 @@
     "translation": "Invalid username."
   },
   {
-    "id": "model.channel.is_valid.2_or_more.app_error",
-    "translation": "Name must be 2 or more lowercase alphanumeric characters."
+    "id": "model.channel.is_valid.1_or_more.app_error",
+    "translation": "Name must be 1 or more lowercase alphanumeric character."
   },
   {
     "id": "model.channel.is_valid.create_at.app_error",

model/channel.go

@@ -27,7 +27,7 @@ const (
 	ChannelGroupMinUsers       = 3
 	DefaultChannelName         = "town-square"
 	ChannelDisplayNameMaxRunes = 64
-	ChannelNameMinLength       = 2
+	ChannelNameMinLength       = 1
 	ChannelNameMaxLength       = 64
 	ChannelHeaderMaxRunes      = 1024
 	ChannelPurposeMaxRunes     = 250
@@ -216,7 +216,7 @@ func (o *Channel) IsValid() *AppError {
 	}
 
 	if !IsValidChannelIdentifier(o.Name) {
-		return NewAppError("Channel.IsValid", "model.channel.is_valid.2_or_more.app_error", nil, "id="+o.Id, http.StatusBadRequest)
+		return NewAppError("Channel.IsValid", "model.channel.is_valid.1_or_more.app_error", nil, "id="+o.Id, http.StatusBadRequest)
 	}
 
 	if !(o.Type == ChannelTypeOpen || o.Type == ChannelTypePrivate || o.Type == ChannelTypeDirect || o.Type == ChannelTypeGroup) {

model/shared_channel.go

@@ -51,7 +51,7 @@ func (sc *SharedChannel) IsValid() *AppError {
 	}
 
 	if !IsValidChannelIdentifier(sc.ShareName) {
-		return NewAppError("SharedChannel.IsValid", "model.channel.is_valid.2_or_more.app_error", nil, "id="+sc.ChannelId, http.StatusBadRequest)
+		return NewAppError("SharedChannel.IsValid", "model.channel.is_valid.1_or_more.app_error", nil, "id="+sc.ChannelId, http.StatusBadRequest)
 	}
 
 	if utf8.RuneCountInString(sc.ShareHeader) > ChannelHeaderMaxRunes {

model/utils.go

@@ -510,21 +510,13 @@ var reservedName = []string{
 }
 
 func IsValidChannelIdentifier(s string) bool {
-
-	if !IsValidAlphaNumHyphenUnderscore(s, true) {
-		return false
-	}
-
-	if len(s) < ChannelNameMinLength {
-		return false
-	}
-
-	return true
+	return validSimpleAlphaNum.MatchString(s) && len(s) >= ChannelNameMinLength
 }
 
 var (
 	validAlphaNum                           = regexp.MustCompile(`^[a-z0-9]+([a-z\-0-9]+|(__)?)[a-z0-9]+$`)
 	validAlphaNumHyphenUnderscore           = regexp.MustCompile(`^[a-z0-9]+([a-z\-\_0-9]+|(__)?)[a-z0-9]+$`)
+	validSimpleAlphaNum                     = regexp.MustCompile(`^[a-z0-9]+([a-z\-\_0-9]+|(__)?)[a-z0-9]*$`)
 	validSimpleAlphaNumHyphenUnderscore     = regexp.MustCompile(`^[a-zA-Z0-9\-_]+$`)
 	validSimpleAlphaNumHyphenUnderscorePlus = regexp.MustCompile(`^[a-zA-Z0-9+_-]+$`)
 )

model/utils_test.go

@@ -862,6 +862,55 @@ func TestSanitizeUnicode(t *testing.T) {
 	}
 }
 
+func TestIsValidChannelIdentifier(t *testing.T) {
+	cases := []struct {
+		Description string
+		Input       string
+		Expected    bool
+	}{
+		{
+			Description: "less than min length",
+			Input:       "",
+			Expected:    false,
+		},
+		{
+			Description: "single alphabetical char",
+			Input:       "a",
+			Expected:    true,
+		},
+		{
+			Description: "single underscore",
+			Input:       "_",
+			Expected:    false,
+		},
+		{
+			Description: "single hyphen",
+			Input:       "-",
+			Expected:    false,
+		},
+		{
+			Description: "empty string",
+			Input:       " ",
+			Expected:    false,
+		},
+		{
+			Description: "multiple with hyphen",
+			Input:       "a-a",
+			Expected:    true,
+		},
+		{
+			Description: "multiple with hyphen",
+			Input:       "a_a",
+			Expected:    true,
+		},
+	}
+
+	for _, tc := range cases {
+		actual := IsValidChannelIdentifier(tc.Input)
+		require.Equalf(t, actual, tc.Expected, "case: '%v'\tshould returned: %#v", tc.Input, tc.Expected)
+	}
+}
+
 func TestIsValidHTTPURL(t *testing.T) {
 	t.Parallel()