Re-land the sonic decl/impl split with fallback discovery parse reuse

.github/instructions/Razor.instructions.md

@@ -40,6 +40,12 @@ their original sub-tree layout
   `solution.GetDocumentIdsWithFilePath(filePath)` then `solution.GetAdditionalDocument(documentId)`.
 - **Remote services**: Place the public stub method (calling `RunServiceAsync`) directly
   above its private implementation method.
+- **Formatting options across OOP**: Cohost endpoints must read
+  `CSharpSyntaxFormattingOptions` from the local Roslyn solution services and include them in
+  `RazorFormattingOptions` sent to remote formatting consumers. Remote `IClientSettingsManager`
+  state does not contain the user's C# formatting preferences, so do not reconstruct them OOP.
+  Resolve the options at the public handler boundary and keep downstream product parameters
+  non-null.
 - **Runtime-declared attribute lists**: When the runtime declares a set the compiler must read
   (e.g. `[EventHandler]`, `[AcceptsAssetPath]`), it applies the attributes to a public type with
   a well-known name (`EventHandlers`, `AssetPathAttributes`). A `TagHelperProducer` under

.github/memory/testing/razor.md

@@ -14,18 +14,24 @@ Layer-specific test guidance for Razor tooling/compiler tests under `src/Razor`.
 - Test end-user scenarios, not implementation details.
 - Verify/helper methods go at the bottom of test files; new test methods go above
   them.
-- New tooling tests go in
-  `src\Razor\src\Razor\test\Microsoft.VisualStudioCode.RazorExtension.UnitTests`
-  (Cohosting architecture).
+- Shared cohost endpoint tests go in
+  `src\Razor\src\Razor\test\Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests`
+  and must be listed in its `.projitems` file; both the Visual Studio and VS Code
+  unit-test projects import that suite.
 - Integration tests using `AdditionalSyntaxTrees` for tag helper discovery must
   set `UseTwoPhaseCompilation => true` (see `ComponentDiscoveryIntegrationTest`).
   Under two-phase compilation the `AdditionalSyntaxTrees` are compiled into a
   temp assembly and added as a *reference*, so discovery sees those types as
   coming from a referenced assembly (not source).
+- Regenerate baseline-backed compiler tests with a targeted test filter and
+  `/p:GenerateBaselines=true` on one CoreCLR target framework, then rerun the
+  tests normally. Two-phase tests can produce `.decl.codegen.cs` and
+  `.decl.mappings.txt` in addition to implementation and component
+  `.builder.txt` baselines.
 - After Razor compiler tests or their `TestFiles` change, run the complete
   affected test project. A successful build does not validate embedded
   baseline resources.
-
+  
 ## Baseline (codegen) tests
 
 - `ComponentCodeGenerationTestBase` and similar baseline tests assert generated

.github/skills/merge-into-branch/SKILL.md

@@ -98,11 +98,42 @@ dotnet run --file eng/generate-compiler-code.cs
 
 Review and stage any generated changes before finishing the merge.
 
-#### 3d. Other conflicts
+#### 3d. Razor compiler baselines and tests
+
+If the merge changes files under `src/Razor/src/Compiler`, identify and run every affected test project before presenting the merge as ready.
+
+If baseline-backed Razor compiler tests or their `TestFiles` change:
+
+1. Identify the affected fully qualified test names from the changed test methods and baseline directories.
+2. Regenerate those baselines on one CoreCLR target framework to avoid concurrent writers:
+
+   ```bash
+   dotnet test <test-project> --framework <coreclr-tfm> --filter "<affected-tests>" -p:GenerateBaselines=true
+   ```
+
+   Always use a targeted filter when generating baselines because the unfiltered suite includes `GenerateBaselinesMustBeFalse`, which intentionally fails while generation is enabled.
+3. Review all generated changes. Two-phase Razor tests may add or update `.decl.codegen.cs` and `.decl.mappings.txt` alongside `.codegen.cs`, `.mappings.txt`, `.ir.txt`, `.diagnostics.txt`, and component `.builder.txt` files.
+4. Rerun the affected tests normally, without `GenerateBaselines=true`.
+5. Run the complete affected test project normally so newly added or auto-merged tests are not missed:
+
+   ```bash
+   dotnet test <test-project>
+   ```
+
+Common Razor compiler test projects include:
+
+- `src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/Microsoft.AspNetCore.Razor.Language.UnitTests.csproj`
+- `src/Razor/src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions/test/Microsoft.AspNetCore.Mvc.Razor.Extensions.UnitTests.csproj`
+- `src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor/test/Microsoft.CodeAnalysis.Razor.UnitTests.csproj`
+- `src/Razor/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.UnitTests/Microsoft.NET.Sdk.Razor.SourceGenerators.UnitTests.csproj`
+
+An analyzer build is not a substitute for these tests. Do not sign off on the merge until baseline generation has been reviewed and all affected test projects pass.
+
+#### 3e. Other conflicts
 
 Resolve any remaining conflicts carefully using the repo's existing code patterns. Avoid unrelated cleanup or opportunistic edits during the merge.
 
-#### 3e. Validate the merge after conflict resolution
+#### 3f. Validate the merge after conflict resolution
 
 Before presenting the summary or creating the merge commit, run a validating build with analyzers enabled to make sure the merge did not introduce new issues:
 
@@ -128,9 +159,11 @@ Once all conflicts are resolved and staged, present a concise but specific summa
    - `.xlf` → accepted ours and updated XLFs
    - `.resx` → manually merged to preserve all strings and updated XLFs
    - `src/Compilers` → reran compiler code generation
+   - Razor compiler tests → regenerated and reviewed affected baselines, reran targeted tests, and ran the complete affected test projects
    - other files → briefly describe the manual resolution
-4. The result of the post-merge validation build/analyzer run.
-5. A diff summary using commands such as:
+4. The exact post-merge test commands and results, including affected test-project totals.
+5. The result of the post-merge validation build/analyzer run.
+6. A diff summary using commands such as:
 
 ```bash
 git status --short

src/LanguageServer/Protocol/Handler/CallHierarchy/PrepareCallHierarchyHandler.cs

@@ -30,9 +30,13 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(LSP.CallHierarchyPrepare
         => request.TextDocument;
 
     public async Task<LSP.CallHierarchyItem[]?> HandleRequestAsync(LSP.CallHierarchyPrepareParams request, RequestContext context, CancellationToken cancellationToken)
-        => await PrepareCallHierarchyAsync(context.GetRequiredDocument(), ProtocolConversions.PositionToLinePosition(request.Position), cancellationToken).ConfigureAwait(false);
+    {
+        var document = context.GetRequiredDocument();
+        return await PrepareCallHierarchyAsync(document, ProtocolConversions.PositionToLinePosition(request.Position), document.Id, cancellationToken)
+            .ConfigureAwait(false);
+    }
 
-    internal static async Task<LSP.CallHierarchyItem[]?> PrepareCallHierarchyAsync(Document document, LinePosition linePosition, CancellationToken cancellationToken)
+    internal static async Task<LSP.CallHierarchyItem[]?> PrepareCallHierarchyAsync(Document document, LinePosition linePosition, DocumentId preferredDocumentId, CancellationToken cancellationToken)
     {
         var solution = document.Project.Solution;
         var position = await document.GetPositionFromLinePositionAsync(linePosition, cancellationToken).ConfigureAwait(false);
@@ -47,7 +51,7 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(LSP.CallHierarchyPrepare
         if (itemDescriptor == null)
             return null;
 
-        var item = await CallHierarchyHelpers.CreateItemAsync(itemDescriptor, solution, preferredDocumentId: document.Id, cancellationToken).ConfigureAwait(false);
+        var item = await CallHierarchyHelpers.CreateItemAsync(itemDescriptor, solution, preferredDocumentId, cancellationToken).ConfigureAwait(false);
         return item == null ? null : [item];
     }
 }

src/LanguageServer/Protocol/Handler/CodeLens/CodeLensHandler.cs

@@ -22,7 +22,7 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.CodeLens;
 
 [ExportCSharpVisualBasicStatelessLspService(typeof(CodeLensHandler)), Shared]
 [Method(LSP.Methods.TextDocumentCodeLensName)]
-internal sealed class CodeLensHandler : ILspServiceDocumentRequestHandler<LSP.CodeLensParams, LSP.CodeLens[]?>
+internal sealed class CodeLensHandler : ILspServiceDocumentRequestHandler<LSP.CodeLensParams, LSP.CodeLens[]>
 {
     public const string RunTestsCommandIdentifier = "dotnet.test.run";
 
@@ -42,10 +42,10 @@ public CodeLensHandler(IGlobalOptionService globalOptionService)
     public LSP.TextDocumentIdentifier GetTextDocumentIdentifier(LSP.CodeLensParams request)
         => request.TextDocument;
 
-    public Task<LSP.CodeLens[]?> HandleRequestAsync(LSP.CodeLensParams request, RequestContext context, CancellationToken cancellationToken)
+    public Task<LSP.CodeLens[]> HandleRequestAsync(LSP.CodeLensParams request, RequestContext context, CancellationToken cancellationToken)
         => GetCodeLensAsync(request.TextDocument, context.GetRequiredDocument(), _globalOptionService, cancellationToken);
 
-    internal static async Task<LSP.CodeLens[]?> GetCodeLensAsync(LSP.TextDocumentIdentifier textDocumentIdentifier, Document document, IGlobalOptionService globalOptionService, CancellationToken cancellationToken)
+    internal static async Task<LSP.CodeLens[]> GetCodeLensAsync(LSP.TextDocumentIdentifier textDocumentIdentifier, Document document, IGlobalOptionService globalOptionService, CancellationToken cancellationToken)
     {
         var referencesCodeLensEnabled = globalOptionService.GetOption(LspOptionsStorage.LspEnableReferencesCodeLens, document.Project.Language);
         var testsCodeLensEnabled = globalOptionService.GetOption(LspOptionsStorage.LspEnableTestsCodeLens, document.Project.Language);
@@ -200,4 +200,3 @@ private static void AddTestCodeLens(
         }
     }
 }
-

src/LanguageServer/Protocol/Handler/Highlights/DocumentHighlightHandler.cs

@@ -46,24 +46,19 @@ public DocumentHighlightsHandler(IHighlightingService highlightingService, IGlob
         if (document == null)
             return null;
 
-        var position = ProtocolConversions.PositionToLinePosition(request.Position);
-        return await GetHighlightsAsync(_globalOptions, _highlightingService, document, position, cancellationToken).ConfigureAwait(false);
-    }
-
-    internal static async Task<DocumentHighlight[]?> GetHighlightsAsync(IGlobalOptionService globalOptions, IHighlightingService highlightingService, Document document, LinePosition linePosition, CancellationToken cancellationToken)
-    {
+        var linePosition = ProtocolConversions.PositionToLinePosition(request.Position);
         var text = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
         var position = await document.GetPositionFromLinePositionAsync(linePosition, cancellationToken).ConfigureAwait(false);
 
         // First check if this is a keyword that needs highlighting.
-        var keywordHighlights = await GetKeywordHighlightsAsync(highlightingService, document, text, position, cancellationToken).ConfigureAwait(false);
+        var keywordHighlights = await GetKeywordHighlightsAsync(document, text, position, cancellationToken).ConfigureAwait(false);
         if (keywordHighlights.Any())
         {
             return [.. keywordHighlights];
         }
 
         // Not a keyword, check if it is a reference that needs highlighting.
-        var referenceHighlights = await GetReferenceHighlightsAsync(globalOptions, document, text, position, cancellationToken).ConfigureAwait(false);
+        var referenceHighlights = await GetReferenceHighlightsAsync(document, text, position, cancellationToken).ConfigureAwait(false);
         if (referenceHighlights.Any())
         {
             return [.. referenceHighlights];
@@ -73,12 +68,12 @@ public DocumentHighlightsHandler(IHighlightingService highlightingService, IGlob
         return [];
     }
 
-    private static async Task<ImmutableArray<DocumentHighlight>> GetKeywordHighlightsAsync(IHighlightingService highlightingService, Document document, SourceText text, int position, CancellationToken cancellationToken)
+    private async Task<ImmutableArray<DocumentHighlight>> GetKeywordHighlightsAsync(Document document, SourceText text, int position, CancellationToken cancellationToken)
     {
         var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
 
         var keywordSpans = new List<TextSpan>();
-        highlightingService.AddHighlights(root, position, keywordSpans, cancellationToken);
+        _highlightingService.AddHighlights(root, position, keywordSpans, cancellationToken);
 
         return keywordSpans.SelectAsArray(highlight => new DocumentHighlight
         {
@@ -87,10 +82,10 @@ private static async Task<ImmutableArray<DocumentHighlight>> GetKeywordHighlight
         });
     }
 
-    private static async Task<ImmutableArray<DocumentHighlight>> GetReferenceHighlightsAsync(IGlobalOptionService globalOptions, Document document, SourceText text, int position, CancellationToken cancellationToken)
+    private async Task<ImmutableArray<DocumentHighlight>> GetReferenceHighlightsAsync(Document document, SourceText text, int position, CancellationToken cancellationToken)
     {
         var documentHighlightService = document.GetRequiredLanguageService<IDocumentHighlightsService>();
-        var options = globalOptions.GetHighlightingOptions(document.Project.Language);
+        var options = _globalOptions.GetHighlightingOptions(document.Project.Language);
         var highlights = await documentHighlightService.GetDocumentHighlightsAsync(
             document,
             position,

src/Razor/src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/test/IntegrationTests/CodeGenerationIntegrationTest.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 #nullable disable
@@ -44,11 +44,11 @@ public class MyService<TModel>
 
         // Assert
         AssertDocumentNodeMatchesBaseline(compiled.CodeDocument.GetDocumentNode());
-        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetCSharpDocument());
+        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetImplCSharpDocument());
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
 
         // We expect this test to generate a bunch of errors.
-        Assert.True(compiled.CodeDocument.GetCSharpDocument().Diagnostics.Length > 0);
+        Assert.True(compiled.CodeDocument.GetImplCSharpDocument().Diagnostics.Length > 0);
     }
 
     [Fact]
@@ -69,7 +69,7 @@ public class MyApp
 
         // Assert
         AssertDocumentNodeMatchesBaseline(compiled.CodeDocument.GetDocumentNode());
-        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetCSharpDocument());
+        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetImplCSharpDocument());
         AssertLinePragmas(compiled.CodeDocument);
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
     }
@@ -101,7 +101,7 @@ public class MyApp
 
         // Assert
         AssertDocumentNodeMatchesBaseline(compiled.CodeDocument.GetDocumentNode());
-        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetCSharpDocument());
+        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetImplCSharpDocument());
         AssertLinePragmas(compiled.CodeDocument);
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
     }
@@ -134,7 +134,7 @@ public class MyService<TModel>
 
         // Assert
         AssertDocumentNodeMatchesBaseline(compiled.CodeDocument.GetDocumentNode());
-        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetCSharpDocument());
+        AssertCSharpDocumentMatchesBaseline(compiled.CodeDocument.GetImplCSharpDocument());
         AssertLinePragmas(compiled.CodeDocument);
         AssertSourceMappingsMatchBaseline(compiled.CodeDocument);
     }

src/Razor/src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/test/ModelExpressionPassTest.cs

@@ -21,7 +21,7 @@ protected override void ConfigureProjectEngine(RazorProjectEngineBuilder builder
 
     protected override void ConfigureCodeDocumentProcessor(RazorCodeDocumentProcessor processor)
     {
-        processor.ExecutePhasesThrough<IRazorDocumentClassifierPhase>();
+        processor.ExecutePhasesThrough<DefaultRazorTagHelperRewritePhase>();
     }
 
     [Fact]

src/Razor/src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/test/ViewComponentTagHelperPassTest.cs

@@ -20,7 +20,7 @@ protected override void ConfigureProjectEngine(RazorProjectEngineBuilder builder
 
     protected override void ConfigureCodeDocumentProcessor(RazorCodeDocumentProcessor processor)
     {
-        processor.ExecutePhasesThrough<IRazorDocumentClassifierPhase>();
+        processor.ExecutePhasesThrough<DefaultRazorTagHelperRewritePhase>();
 
         // We also expect the default tag helper pass to run first.
         processor.ExecutePass<DefaultTagHelperOptimizationPass>();