Refresh stale C# indexes for tuple fields (#4616)

Author: Widthdom

TESTING_GUIDE.md

@@ -190,7 +190,7 @@ Use `docs/test-doc-maintenance-plan.md` before moving oversized suites or adding
   C# query-range collision forms for basic selection, directional ordering, keyword-named members, and object initializers share one indexed source when they assert the same empty inspect reference bundle.
   C# inspect brace-range regressions place char-literal, raw-string, and verbatim-string forms in one indexed class and query each following method from that shared fixture.
   C# generic query-range selectors share simple and tuple type arguments in one fixture, while generic type-pattern coverage shares designation and no-designation forms in another fixture.
-  C# field-type grammar coverage shares static readonly tuple, nullable-tuple, generic-tuple-member, const/plain-field controls, and deconstruction negatives in one extractor fixture.
+  C# field-type grammar coverage shares static readonly tuple, nullable-tuple, generic-tuple-member, const/plain-field controls, and deconstruction negatives in one extractor fixture. The full-scan regression also seeds the previous C# extractor contract against an unchanged file and verifies that incremental indexing restores the tuple field kind and complete return type.
   C# switch-expression pattern-variable coverage keeps recursive, declaration, guard, and comment-trivia forms in one extractor fixture when their contract is the set of genuine enum-member references.
   C# foreach-shadowing coverage shares embedded, same-line, and dangling-else forms in one source and distinguishes the surviving references by container.
   C# lambda-parameter shadowing coverage shares simple, multiline, after-lambda, and same-line boundary forms in one extraction pass.
@@ -889,7 +889,7 @@ dotnet test --filter "FullyQualifiedName~GitHelperTests"
   C# query-range collision の basic selection、directional ordering、keyword 名 member、object initializer は、同じ空の inspect reference bundle を検証する場合は1つの indexed source を共有してください。
   C# inspect の brace-range regression は char literal、raw string、verbatim string を1つの indexed class に併置し、それぞれの後続 method を共有 fixture から query してください。
   C# generic query-range selector は単純型引数と tuple 型引数を1つの fixture で共有し、generic type-pattern coverage は designation 有無を別の1 fixture で共有してください。
-  C# field 型文法 coverage は static readonly tuple、nullable tuple、generic 内 tuple member、const / 通常 field の control、deconstruction の負例を1つの extractor fixture で共有してください。
+  C# field 型文法 coverage は static readonly tuple、nullable tuple、generic 内 tuple member、const / 通常 field の control、deconstruction の負例を1つの extractor fixture で共有してください。full-scan regression では未変更 file に以前の C# extractor contract を設定し、incremental index が tuple field の kind と完全な return type を復元することも検証してください。
   C# switch-expression pattern-variable coverage は、真の enum-member reference 集合を同じ contract とする recursive、declaration、guard、comment-trivia 形式を1つの extractor fixture で共有してください。
   C# foreach shadowing coverage は embedded、same-line、dangling-else 形式を1つの source で共有し、残る reference を container で区別してください。
   C# lambda parameter shadowing coverage は simple、multiline、after-lambda、same-line boundary 形式を1回の extraction pass で共有してください。

changelog.d/unreleased/4616.fixed.md

@@ -5,12 +5,13 @@ issues:
 affected:
   - src/CodeIndex/Indexer/Symbols/SymbolExtractor.cs
   - tests/CodeIndex.Tests/SymbolExtractorCSharpTests.cs
+  - tests/CodeIndex.Tests/IndexCommandRunnerFullScanTests.cs
 ---
 
 ## English
 
-- **C# static readonly tuple fields retain complete metadata (#4616)** — static readonly fields now use the shared C# type grammar, so tuple, nullable-tuple, and generic-tuple-member types remain `field` symbols with complete return-type metadata without treating deconstruction locals as fields.
+- **C# static readonly tuple fields retain complete metadata (#4616)** — static readonly fields now use the shared C# type grammar, so tuple, nullable-tuple, and generic-tuple-member types remain `field` symbols with complete return-type metadata without treating deconstruction locals as fields. The C# extractor contract was advanced so normal incremental indexing refreshes unchanged source files created by earlier versions.
 
 ## 日本語
 
-- **C# の static readonly tuple field で完全なメタデータを保持するようになりました (#4616)** — static readonly field が共有 C# 型文法を使うようになり、tuple、nullable tuple、generic 内の tuple member 型を deconstruction local と誤認せず、完全な return-type metadata を持つ `field` symbol として維持します。
+- **C# の static readonly tuple field で完全なメタデータを保持するようになりました (#4616)** — static readonly field が共有 C# 型文法を使うようになり、tuple、nullable tuple、generic 内の tuple member 型を deconstruction local と誤認せず、完全な return-type metadata を持つ `field` symbol として維持します。C# extractor contract も更新したため、通常の incremental index で以前の version が作成した未変更 source file を再抽出します。

src/CodeIndex/Indexer/Symbols/SymbolExtractor.cs

@@ -15,7 +15,7 @@ public static partial class SymbolExtractor
 {
     public const int DefaultContractVersion = 1;
     public const int ExpandedLanguageContractVersion = 2;
-    public const int CSharpContractVersion = 3;
+    public const int CSharpContractVersion = 4;
     public const int DockerfileContractVersion = 2;
     public const int MakefileContractVersion = 2;
     public const int StyleAndXamlContractVersion = 2;

tests/CodeIndex.Tests/IndexCommandRunnerFullScanTests.cs

@@ -2030,6 +2030,68 @@ WHERE kind IN ('route', 'implements', 'attribute', 'layout')
         }
     }
 
+    [Fact]
+    public void Run_FullScan_ReindexesUnchangedCSharpTupleReadonlyFieldWhenExtractorVersionChanged_Issue4616()
+    {
+        var projectRoot = CreateTempProject();
+        try
+        {
+            File.WriteAllText(
+                Path.Combine(projectRoot, "tuple-fields.cs"),
+                """
+                public class TupleFields
+                {
+                    public static readonly (int Left, int Right) Pair = (1, 2);
+                }
+                """);
+
+            var initialExitCode = IndexCommandRunner.Run([projectRoot, "--json"], _jsonOptions);
+            Assert.Equal(CommandExitCodes.Success, initialExitCode);
+
+            var dbPath = Path.Combine(projectRoot, ".cdidx", "codeindex.db");
+            using (var conn = OpenNonPoolingConnection(dbPath))
+            {
+                conn.Open();
+                using var cmd = conn.CreateCommand();
+                cmd.CommandText = $"""
+                    DELETE FROM symbols WHERE name = 'Pair';
+                    UPDATE codeindex_meta
+                    SET value = '3'
+                    WHERE key = '{DbContext.GetSymbolExtractorVersionMetaKey("csharp")}';
+                    """;
+                cmd.ExecuteNonQuery();
+            }
+
+            var (exitCode, json) = RunAndCaptureJson([projectRoot, "--json"]);
+
+            Assert.Equal(CommandExitCodes.Success, exitCode);
+            Assert.Equal("success", json.GetProperty("status").GetString());
+            Assert.Equal(0, json.GetProperty("summary").GetProperty("files_skipped").GetInt32());
+
+            using var verify = OpenNonPoolingConnection(dbPath);
+            verify.Open();
+            using var symbolCmd = verify.CreateCommand();
+            symbolCmd.CommandText = "SELECT kind, return_type FROM symbols WHERE name = 'Pair'";
+            using (var reader = symbolCmd.ExecuteReader())
+            {
+                Assert.True(reader.Read());
+                Assert.Equal("field", reader.GetString(0));
+                Assert.Equal("(int Left, int Right)", reader.GetString(1));
+                Assert.False(reader.Read());
+            }
+
+            using var versionCmd = verify.CreateCommand();
+            versionCmd.CommandText = $"SELECT value FROM codeindex_meta WHERE key = '{DbContext.GetSymbolExtractorVersionMetaKey("csharp")}'";
+            Assert.Equal(
+                SymbolExtractor.CSharpContractVersion.ToString(System.Globalization.CultureInfo.InvariantCulture),
+                versionCmd.ExecuteScalar() as string);
+        }
+        finally
+        {
+            DeleteDirectory(projectRoot);
+        }
+    }
+
     [ProductionRuntimeFact]
     public void Run_FullScan_DegradedWarningSummarizesRemainingFoldGap()
     {