Only walk the changes to determine if there was a problematic formatting difference

Author: ToddGrun

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/SourceTextExtensions.cs

@@ -60,8 +60,25 @@ public static string GetSubTextString(this SourceText text, TextSpan span)
         return new string(charBuffer, 0, span.Length);
     }
 
-    public static bool NonWhitespaceContentEquals(this SourceText text, SourceText other)
-        => NonWhitespaceContentEquals(text, other, 0, text.Length, 0, other.Length);
+    public static bool NonWhitespaceContentEquals(this SourceText text, ImmutableArray<TextChange> changes)
+    {
+        foreach (var change in changes)
+        {
+            if (!text.NonWhitespaceContentEquals(change))
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    public static bool NonWhitespaceContentEquals(this SourceText text, TextChange change)
+    {
+        var other = change.NewText ?? string.Empty;
+
+        return NonWhitespaceContentEquals(text, i => other[i], change.Span.Start, change.Span.End, 0, other.Length);
+    }
 
     public static bool NonWhitespaceContentEquals(
         this SourceText text,
@@ -70,22 +87,36 @@ public static bool NonWhitespaceContentEquals(
         int textEnd,
         int otherStart,
         int otherEnd)
+    {
+        return NonWhitespaceContentEquals(text, i => other[i], textStart, textEnd, otherStart, otherEnd);
+    }
+
+    public static bool NonWhitespaceContentEquals(
+        this SourceText text,
+        Func<int, char> getOtherCharAt,
+        int textStart,
+        int textEnd,
+        int otherStart,
+        int otherEnd)
     {
         var i = textStart;
         var j = otherStart;
         while (i < textEnd && j < otherEnd)
         {
-            if (char.IsWhiteSpace(text[i]))
+            var textChar = text[i];
+            if (char.IsWhiteSpace(textChar))
             {
                 i++;
                 continue;
             }
-            else if (char.IsWhiteSpace(other[j]))
+
+            var otherChar = getOtherCharAt(j);
+            if (char.IsWhiteSpace(otherChar))
             {
                 j++;
                 continue;
             }
-            else if (text[i] != other[j])
+            else if (textChar != otherChar)
             {
                 return false;
             }
@@ -99,7 +130,7 @@ public static bool NonWhitespaceContentEquals(
             i++;
         }
 
-        while (j < otherEnd && char.IsWhiteSpace(other[j]))
+        while (j < otherEnd && char.IsWhiteSpace(getOtherCharAt(j)))
         {
             j++;
         }

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/Passes/FormattingContentValidationPass.cs

@@ -23,9 +23,8 @@ internal sealed class FormattingContentValidationPass(ILoggerFactory loggerFacto
     public Task<bool> IsValidAsync(FormattingContext context, ImmutableArray<TextChange> changes, CancellationToken cancellationToken)
     {
         var text = context.SourceText;
-        var changedText = text.WithChanges(changes);
 
-        if (!text.NonWhitespaceContentEquals(changedText))
+        if (!text.NonWhitespaceContentEquals(changes))
         {
             // Looks like we removed some non-whitespace content as part of formatting. Oops.
             // Discard this formatting result.