Log when formatting operations are being abandoned (#9617)

Author: davidwengier

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Extensions/RangeExtensions.cs

@@ -130,4 +130,9 @@ public static int CompareTo(this Range range1, Range range2)
 
         return result;
     }
+
+    public static string ToDisplayString(this Range range)
+    {
+        return $"({range.Start.Line}, {range.Start.Character})-({range.End.Line}, {range.End.Character})";
+    }
 }

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Formatting/FormattingContentValidationPass.cs

@@ -57,6 +57,21 @@ public override Task<FormattingResult> ExecuteAsync(FormattingContext context, F
             // Looks like we removed some non-whitespace content as part of formatting. Oops.
             // Discard this formatting result.
 
+            _logger.LogWarning("{value}", SR.Format_operation_changed_nonwhitespace);
+
+            foreach (var edit in edits)
+            {
+                if (edit.NewText.Any(c => !char.IsWhiteSpace(c)))
+                {
+                    _logger.LogWarning("{value}", SR.FormatEdit_at_adds(edit.Range.ToDisplayString(), edit.NewText));
+                }
+                else if (text.GetSubText(edit.Range.ToTextSpan(text)) is { } subText &&
+                    subText.GetFirstNonWhitespaceOffset(span: null, out _) is not null)
+                {
+                    _logger.LogWarning("{value}", SR.FormatEdit_at_deletes(edit.Range.ToDisplayString(), subText.ToString()));
+                }
+            }
+
             if (DebugAssertsEnabled)
             {
                 Debug.Fail("A formatting result was rejected because it was going to change non-whitespace content in the document.");

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Formatting/FormattingDiagnosticValidationPass.cs

@@ -65,6 +65,23 @@ public async override Task<FormattingResult> ExecuteAsync(FormattingContext cont
         // at all possible). Also worth noting the order has to be maintained in that case.
         if (!originalDiagnostics.SequenceEqual(changedDiagnostics, LocationIgnoringDiagnosticComparer.Instance))
         {
+            // Yes, these log messages look weird, but this is how structured logging works. The first parameter, the "template" is not
+            // supposed to change, or it causes lots of allocations. The second parameter is the "argument" which is supposed to change.
+            // In our case, we never use structured logging such that the argument name is important, so we just use the same one, and
+            // save some memory, and still log the expected values.
+            _logger.LogWarning("{value}", SR.Format_operation_changed_diagnostics);
+            _logger.LogWarning("{value}", SR.Diagnostics_before);
+            foreach (var diagnostic in originalDiagnostics)
+            {
+                _logger.LogWarning("{value}", diagnostic);
+            }
+
+            _logger.LogWarning("{value}", SR.Diagnostics_after);
+            foreach (var diagnostic in changedDiagnostics)
+            {
+                _logger.LogWarning("{value}", diagnostic);
+            }
+
             if (DebugAssertsEnabled)
             {
                 Debug.Fail("A formatting result was rejected because the formatted text produced different diagnostics compared to the original text.");

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Resources/SR.resx

@@ -120,18 +120,39 @@
   <data name="Blazor_directive_attributes" xml:space="preserve">
     <value>Blazor directive attributes</value>
   </data>
+  <data name="Changes" xml:space="preserve">
+    <value>Changes:</value>
+  </data>
   <data name="Create_Component_FromTag_Title" xml:space="preserve">
     <value>Create component from tag</value>
   </data>
+  <data name="Diagnostics_after" xml:space="preserve">
+    <value>Diagnostics after:</value>
+  </data>
+  <data name="Diagnostics_before" xml:space="preserve">
+    <value>Diagnostics before:</value>
+  </data>
   <data name="Document_Not_Found" xml:space="preserve">
     <value>Document {0} was not found.</value>
   </data>
+  <data name="Edit_at_adds" xml:space="preserve">
+    <value>Edit at {0} adds the non-whitespace content '{1}'.</value>
+  </data>
+  <data name="Edit_at_deletes" xml:space="preserve">
+    <value>Edit at {0} deletes the non-whitespace content '{1}'.</value>
+  </data>
   <data name="ExtractTo_CodeBehind_Title" xml:space="preserve">
     <value>Extract block to code behind</value>
   </data>
   <data name="File_Externally_Modified" xml:space="preserve">
     <value>File was externally modified: {0}</value>
   </data>
+  <data name="Format_operation_changed_diagnostics" xml:space="preserve">
+    <value>A format operation is being abandoned because it would introduce or remove one of more diagnostics.</value>
+  </data>
+  <data name="Format_operation_changed_nonwhitespace" xml:space="preserve">
+    <value>A format operation is being abandoned because it would add or delete non-whitespace content.</value>
+  </data>
   <data name="Generate_Async_Event_Handler_Title" xml:space="preserve">
     <value>Generate Async Event Handler '{0}'</value>
   </data>