handle unassigned code points, as they're also invisible

CompatBot/EventHandlers/UsernameZalgoMonitor.cs

@@ -60,6 +60,7 @@ namespace CompatBot.EventHandlers
 
                     case UnicodeCategory.Control:
                     case UnicodeCategory.Format:
+                    case UnicodeCategory.OtherNotAssigned when c >= 0xdb40:
                         break;
 
                     default:

CompatBot/Utils/StringUtils.cs

@@ -60,12 +60,40 @@ namespace CompatBot.Utils
 
             int start, end;
             for (start = 0; start < str.Length; start++)
-                if (!char.IsWhiteSpace(str[start]) && !IsFormat(str[start]))
-                    break;
+            {
+                if (char.IsWhiteSpace(str, start) || IsFormat(str[start]))
+                    continue;
+
+                if (char.IsHighSurrogate(str, start)
+                    && char.GetUnicodeCategory(str, start) == UnicodeCategory.OtherNotAssigned
+                    && str[start] >= 0xdb40) // this will check if the surrogate pair is >= E0000 (see https://en.wikipedia.org/wiki/UTF-16#U+010000_to_U+10FFFF)
+                    continue;
+
+                if (char.IsLowSurrogate(str, start))
+                    continue;
+
+                break;
+            }
 
             for (end = str.Length - 1; end >= start; end--)
-                if (!char.IsWhiteSpace(str[end]) && !IsFormat(str[end]))
-                    break;
+            {
+                if (char.IsWhiteSpace(str, end) || IsFormat(str[end]))
+                    continue;
+
+                if (char.IsLowSurrogate(str, end)
+                    && end > start
+                    && char.IsHighSurrogate(str, end - 1)
+                    && char.GetUnicodeCategory(str, end - 1) == UnicodeCategory.OtherNotAssigned
+                    && str[end-1] >= 0xdb40)
+                    continue;
+
+                if (char.IsHighSurrogate(str, end)
+                    && char.GetUnicodeCategory(str, end) == UnicodeCategory.OtherNotAssigned
+                    && str[end] >= 0xdb40)
+                    continue;
+
+                break;
+            }
 
             return CreateTrimmedString(str, start, end);
         }

Tests/ZalgoTests.cs

@@ -36,8 +36,12 @@ namespace Tests
         [TestCase("GodPan กับยูนิตแขนที่หายไป", false)]
         [TestCase("⛧Bζ͜͡annerBomb⛧", false)]
         [TestCase("(_A_Y_A_Z_)  (͡๏̯͡๏)", false)]
+        [TestCase("🥛🥛", false)]
         [TestCase("🎮P̷͙͋a̵̛̳k̶̫̀o̸̿͜ỏ̸̝🎮", true)]
         [TestCase("Cindellด้้้", true)]
+        [TestCase("󠂪󠂪󠂪󠂪 󠂪󠂪󠂪󠂪󠂪󠂪󠂪󠂪 󠂪󠂪󠂪", true)]
+        [TestCase("󠀀󠀀", true)]
+        [TestCase("", true)]
         public void ZalgoDetectionTest(string name, bool isBad)
         {
             Assert.That(UsernameZalgoMonitor.NeedsRename(name), Is.EqualTo(isBad));