ui-common: Show mention suggestions after non-alphanumeric dividers

stream-chat-android-ui-common/src/main/kotlin/io/getstream/chat/android/ui/common/feature/messages/composer/typing/TypingSuggester.kt

@@ -38,10 +38,11 @@ internal class TypingSuggester(private val options: TypingSuggestionOptions) {
             return null
         }
 
-        // Only show typing suggestions after a space, or at the start of the input
-        // valid examples: "@user", "Hello @user"
-        // invalid examples: "Hello@user"
-        val isValidPosition = firstSymbolBeforeCaret == 0 || text[firstSymbolBeforeCaret - 1].isWhitespace()
+        // The symbol must not be glued to a letter or digit.
+        // valid: "@user", "Hello @user", "@user,@user2"
+        // invalid: "Hello@user"
+        val charBeforeSymbol = text.getOrNull(firstSymbolBeforeCaret - 1)
+        val isValidPosition = charBeforeSymbol?.isLetterOrDigit() != true
         if (!isValidPosition) {
             return null
         }

stream-chat-android-ui-common/src/test/kotlin/io/getstream/chat/android/ui/common/feature/messages/composer/typing/TypingSuggesterTest.kt

@@ -45,6 +45,10 @@ internal class TypingSuggesterTest {
             Arguments.of("@ ", null),
             Arguments.of("@  john", null),
             Arguments.of("Hello@john", null),
+            Arguments.of("@john,@jane", TypingSuggestion("jane", 7 until 11)),
+            Arguments.of("@john, @jane", TypingSuggestion("jane", 8 until 12)),
+            Arguments.of("(@john", TypingSuggestion("john", 2 until 6)),
+            Arguments.of("john@example.com", null),
         )
     }
 }