fix(claude-do): merge preview_merge_set: don't report a symbol as removed when the

ClaudeDo-Task: 4882c459-374c-4afe-a60d-2b25b8cce407

src/ClaudeDo.Worker/External/MergeMcpTools.cs

@@ -744,7 +744,7 @@ public sealed class MergeMcpTools
     // One line of a unified diff, tagged with the file it belongs to ('-'/'+' only; context lines
     // are dropped). File is set from the `diff --git a/<path> b/<path>` header, which (unlike
     // `+++ b/...`) is present and names the real path even for a deleted file (`+++ /dev/null`).
-    private readonly record struct DiffLine(string? File, char Sign, string Text);
+    internal readonly record struct DiffLine(string? File, char Sign, string Text);
 
     private static List<DiffLine> ParseDiffLines(string diff)
     {
@@ -783,22 +783,64 @@ public sealed class MergeMcpTools
         @"|[\w<>\[\],.?]+\??\s+(?<name>[A-Za-z_]\w*)\s*(?:\(|\{|=>|;|=))",
         RegexOptions.Compiled);
 
-    private static List<RemovedSymbolDto> ExtractRemovedSymbols(List<DiffLine> diffLines)
+    private static bool IsScannedFile(string? file)
+        => file is not null &&
+           !file.EndsWith(".axaml", StringComparison.OrdinalIgnoreCase) &&
+           !file.EndsWith(".json", StringComparison.OrdinalIgnoreCase);
+
+    // Names this diff declares on '+' lines, per file. A [ObservableProperty] field `_camelName` /
+    // `camelName` generates `CamelName`, so it counts as declaring that; the attribute may sit on its
+    // own '+' line(s) directly above the field.
+    private static HashSet<(string Name, string File)> ExtractAddedDeclarations(List<DiffLine> diffLines)
     {
+        var added = new HashSet<(string Name, string File)>();
+        var observablePending = false;
+        foreach (var line in diffLines)
+        {
+            if (line.Sign != '+' || !IsScannedFile(line.File)) { observablePending = false; continue; }
+
+            var trimmed = line.Text.Trim();
+            var isObservable = trimmed.Contains("[ObservableProperty", StringComparison.Ordinal);
+            if (trimmed.StartsWith('[') && trimmed.EndsWith(']'))
+            {
+                observablePending |= isObservable;
+                continue;
+            }
+
+            var match = RemovedDeclarationRegex.Match(line.Text);
+            if (match.Success)
+            {
+                var name = match.Groups["name"].Value;
+                added.Add((name, line.File!));
+                if (isObservable || observablePending)
+                {
+                    var bare = name.TrimStart('_');
+                    if (bare.Length > 0)
+                        added.Add((char.ToUpperInvariant(bare[0]) + bare[1..], line.File!));
+                }
+            }
+            observablePending = false;
+        }
+        return added;
+    }
+
+    internal static List<RemovedSymbolDto> ExtractRemovedSymbols(List<DiffLine> diffLines)
+    {
+        var added = ExtractAddedDeclarations(diffLines);
         var seen = new HashSet<(string Name, string File)>();
         var result = new List<RemovedSymbolDto>();
         foreach (var line in diffLines)
         {
-            if (line.Sign != '-' || line.File is null) continue;
-            if (line.File.EndsWith(".axaml", StringComparison.OrdinalIgnoreCase) ||
-                line.File.EndsWith(".json", StringComparison.OrdinalIgnoreCase))
-                continue;
+            if (line.Sign != '-' || !IsScannedFile(line.File)) continue;
 
             var match = RemovedDeclarationRegex.Match(line.Text);
             if (!match.Success) continue;
 
-            if (seen.Add((match.Groups["name"].Value, line.File)))
-                result.Add(new RemovedSymbolDto(match.Groups["name"].Value, line.File));
+            var key = (match.Groups["name"].Value, line.File!);
+            if (added.Contains(key)) continue;
+
+            if (seen.Add(key))
+                result.Add(new RemovedSymbolDto(key.Item1, key.Item2));
         }
         return result;
     }

tests/ClaudeDo.Worker.Tests/External/MergeMcpToolsTests.cs

@@ -1359,6 +1359,47 @@ public sealed class MergeMcpToolsTests : IDisposable
         Assert.Equal("Bar.cs", warning.ReferencedInFile);
     }
 
+    private static List<MergeMcpTools.DiffLine> Diff(string file, params string[] lines)
+        => lines.Select(l => new MergeMcpTools.DiffLine(file, l[0], l[1..])).ToList();
+
+    [Fact]
+    public void ExtractRemovedSymbols_AutoPropertyBecomesObservableField_NotReported()
+    {
+        var onOwnLine = Diff("Vm.cs",
+            "-    public bool IsListHandler { get; set; }",
+            "+    [ObservableProperty]",
+            "+    private bool _isListHandler;");
+        var inline = Diff("Vm.cs",
+            "-    public bool IsListHandler { get; set; }",
+            "+    [ObservableProperty] private bool isListHandler;");
+
+        Assert.Empty(MergeMcpTools.ExtractRemovedSymbols(onOwnLine));
+        Assert.Empty(MergeMcpTools.ExtractRemovedSymbols(inline));
+    }
+
+    [Fact]
+    public void ExtractRemovedSymbols_ChangedMethodSignatureInSameFile_NotReported()
+    {
+        var diff = Diff("Foo.cs",
+            "-    public void Run(int a)",
+            "+    public void Run(int a, string b)");
+
+        Assert.Empty(MergeMcpTools.ExtractRemovedSymbols(diff));
+    }
+
+    [Fact]
+    public void ExtractRemovedSymbols_RealRemovalOrCrossFileMove_StillReported()
+    {
+        var diff = Diff("Foo.cs", "-    private void Gone()", "-    public void Moved()")
+            .Concat(Diff("Other.cs", "+    public void Moved()")).ToList();
+
+        var removed = MergeMcpTools.ExtractRemovedSymbols(diff);
+
+        Assert.Equal(2, removed.Count);
+        Assert.Contains(removed, s => s.Name == "Gone" && s.File == "Foo.cs");
+        Assert.Contains(removed, s => s.Name == "Moved" && s.File == "Foo.cs");
+    }
+
     [Fact]
     public async Task PreviewMergeSet_TwoTasksAddDifferentJsonKeys_ReportsNoOverlap()
     {