(GH-824) More strict block comment folding detection

Previously the folder would search for the region markers without case sensitivity.
This commit modifies the regular expressions to be more strict on the what
is a region marker and adds a negative test to ensure that regions that are not
cased correctly are not folded .

Author: glennsarti

src/PowerShellEditorServices/Language/TokenOperations.cs

@@ -24,12 +24,11 @@ internal static class TokenOperations
         // These regular expressions are used to match lines which mark the start and end of region comment in a PowerShell
         // script. They are based on the defaults in the VS Code Language Configuration at;
         // https://github.com/Microsoft/vscode/blob/64186b0a26/extensions/powershell/language-configuration.json#L26-L31
+        // https://github.com/Microsoft/vscode/issues/49070
         static private readonly Regex s_startRegionTextRegex = new Regex(
-           @"^\s*#region\b",
-            RegexOptions.IgnoreCase | RegexOptions.Compiled);
+           @"^\s*#[rR]egion\b", RegexOptions.Compiled);
         static private readonly Regex s_endRegionTextRegex = new Regex(
-           @"^\s*#endregion\b",
-            RegexOptions.IgnoreCase | RegexOptions.Compiled);
+           @"^\s*#[eE]nd[rR]egion\b", RegexOptions.Compiled);
 
         /// <summary>
         /// Extracts all of the unique foldable regions in a script given the list tokens

test/PowerShellEditorServices.Test/Language/TokenOperationsTests.cs

@@ -43,11 +43,11 @@ private static FoldingReference CreateFoldingReference(int startLine, int startC
         // folding regions and regions which should not be
         // detected.  Due to file encoding this could be CLRF or LF line endings
         private const string allInOneScript =
-@"#RegIon This should fold
+@"#Region This should fold
 <#
 Nested different comment types.  This should fold
 #>
-#EnDReGion
+#EndRegion
 
 # region This should not fold due to whitespace
 $shouldFold = $false
@@ -124,6 +124,10 @@ double quoted herestrings should also fold
 ${this
 is
 valid} = 5
+
+#RegIon This should fold due to casing
+$foo = 'bar'
+#EnDReGion
 ";
         private FoldingReference[] expectedAllInOneScriptFolds = {
             CreateFoldingReference(0,   0,  4, 10, "region"),