Move diagnostic generation from LibraryImportGenerator to LibraryImportDiagnosticsAnalyzer #123780

Copilot · 2026-01-29T22:59:01Z

Description

Moves diagnostic generation/emit from the LibraryImportGenerator source generator to a new LibraryImportDiagnosticsAnalyzer in the same assembly, per Roslyn team recommendation.

Changes Made

1. Created `LibraryImportDiagnosticsAnalyzer`

Runs the same diagnostic logic as the generator
Uses SymbolEqualityComparer to compare attribute types instead of string matching
Creates LibraryImportGeneratorOptions once per compilation in RegisterCompilationStartAction
GetDiagnosticIfInvalidMethodForGeneration is internal static so the generator can call it directly

2. Updated `LibraryImportGenerator`

Removed diagnostic reporting from the pipeline
Calls LibraryImportDiagnosticsAnalyzer.GetDiagnosticIfInvalidMethodForGeneration directly to filter methods
No longer uses DiagnosticOr in the pipeline
Removed Diagnostics field from IncrementalStubGenerationContext

3. Updated `CompilationExtensions.GetEnvironmentFlags`

Changed to check for DisableRuntimeMarshallingAttribute on the source assembly instead of the module

4. Updated Test Infrastructure

Added TAnalyzer type parameter to CSharpSourceGeneratorVerifier
Added DisabledDiagnostics.Add(GeneratorDiagnostics.Ids.NotRecommendedGeneratedComInterfaceUsage) to CSharpAnalyzerVerifier
Tests using LibraryImportGenerator use LibraryImportDiagnosticsAnalyzer
Tests using other generators use EmptyDiagnosticAnalyzer

5. Updated Test Files

Diagnostics.cs: Uses CSharpAnalyzerVerifier (analyzer-only testing)
CompileFails.cs: Uses CSharpAnalyzerVerifier for diagnostic tests
ByValueContentsMarshalling.cs: Uses analyzer verifier with SYSLIB1092 re-enabled for specific tests

Test Results

LibraryImportGenerator.Unit.Tests: 702/703 pass (1 skipped)
ComInterfaceGenerator.Unit.Tests: 839/839 pass

Key Architectural Decisions

Analyzer runs independently: The analyzer can run without the generator, making diagnostic-only tests faster
Generator uses analyzer logic: The generator calls the analyzer's GetDiagnosticIfInvalidMethodForGeneration method to share validation logic
Test separation: Tests that verify diagnostics run only the analyzer; tests that verify code generation run both

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… diagnostics Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

…itional analyzer loading Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

…till reports diagnostics) Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Mis-clicked approve

jkoritzinsky

@copilot address this review.

...ime.InteropServices/gen/LibraryImportGenerator/Analyzers/LibraryImportDiagnosticsAnalyzer.cs

...raries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/DiagnosticOr.cs

...aries/System.Runtime.InteropServices/tests/Common/Verifiers/CSharpSourceGeneratorVerifier.cs

…per review feedback Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

...ibraries/System.Runtime.InteropServices/gen/LibraryImportGenerator/LibraryImportGenerator.cs

...braries/System.Runtime.InteropServices/tests/LibraryImportGenerator.UnitTests/Diagnostics.cs

…null, remove helper method Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

…analyzer only Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

jkoritzinsky

@copilot please address the feedback in this review.

...ime.InteropServices/gen/LibraryImportGenerator/Analyzers/LibraryImportDiagnosticsAnalyzer.cs

src/libraries/System.Runtime.InteropServices/tests/Common/Verifiers/CSharpAnalyzerVerifier.cs

...aries/System.Runtime.InteropServices/tests/Common/Verifiers/CSharpSourceGeneratorVerifier.cs

...ibraries/System.Runtime.InteropServices/gen/LibraryImportGenerator/LibraryImportGenerator.cs

...ime.InteropServices/gen/LibraryImportGenerator/Analyzers/LibraryImportDiagnosticsAnalyzer.cs

…ion, simplify verifier, move options Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

jkoritzinsky · 2026-01-31T01:10:05Z

@copilot Please adjust CompilationExtensions.GetEnvironmentFlags to check for DisableRuntimeMarshallingAttribute on the source assembly instead of the module. Also, add handling for the rest of the diagnostic edge cases for the remaining 5% of tests. Then, please remove the Diagnostics field from LibraryImportGenerator.IncrementalStubGenerationContext and remove downstream usages.

…y, remove Diagnostics from generator Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

…ortDiagnosticsAnalyzer Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot · 2026-01-31T01:42:42Z

@copilot Please adjust CompilationExtensions.GetEnvironmentFlags to check for DisableRuntimeMarshallingAttribute on the source assembly instead of the module. Also, add handling for the rest of the di...

Addressed in commits f33ac74 and 9f85c66:

CompilationExtensions.GetEnvironmentFlags - Updated to check compilation.Assembly.GetAttributes() instead of compilation.SourceModule.GetAttributes() for DisableRuntimeMarshallingAttribute.
Removed Diagnostics field - Removed from IncrementalStubGenerationContext record and updated all downstream usages. The generator now uses discarding diagnostics bags and no longer returns diagnostics.
Diagnostic edge cases - Fixed AddDisableRuntimeMarshallingAttributeFixerTests to use LibraryImportDiagnosticsAnalyzer. 28 tests still fail - the analyzer isn't reporting diagnostics for CompileFails.ValidateSnippets tests when run together with the generator. This appears to be related to how the analyzer's RegisterSymbolAction interacts with methods that have compile errors. Investigating further.

jkoritzinsky · 2026-02-02T22:25:54Z

@copilot all of the test failures look like they're due to diagnostics reported by a marshalling generator resolver not being reported from the analyzers.

…c verification Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

…nalyzer verifier Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot · 2026-02-02T23:47:45Z

@copilot all of the test failures look like they're due to diagnostics reported by a marshalling generator resolver not being reported from the analyzers.

Identified and partially fixed. The issue was that CSharpSourceGeneratorTest doesn't properly run analyzer diagnostics verification. Updated tests to use CSharpAnalyzerVerifier instead.

Commits eb6466c and cd49aed:

Changed CompileFails.ValidateSnippets to use analyzer verifier
Changed ByValueContentsMarshalling to use analyzer verifier
Removed CS8795 expectations (not relevant for analyzer-only tests)

Test status: 688/703 pass (14 failing). The 13 array marshalling tests are still failing because the analyzer returns 0 diagnostics for "Marshalling an array from unmanaged to managed requires..." cases. The ManagedToNativeStubGenerator in the analyzer may not be producing these diagnostics correctly. Investigating the marshalling generator resolver path.

Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Initial plan

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Add LibraryImportDiagnosticsAnalyzer and update generator to not emit…

87827dd

… diagnostics Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Fix duplicate diagnostics in LibraryImportDiagnosticsAnalyzer

4e3556e

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Address code review feedback - fix RequiresAllowUnsafeBlocks and cond…

b0d4d92

…itional analyzer loading Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Add LibraryImportDiagnosticsAnalyzer alongside generator (generator s…

deaee03

…till reports diagnostics) Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Move diagnostic generation to analyzers alongside generators~~ Add LibraryImportDiagnosticsAnalyzer foundation for diagnostic migration Jan 29, 2026

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Update CSharpSourceGeneratorVerifier to use TAnalyzer type parameter …

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…per review feedback Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot AI changed the title ~~Add LibraryImportDiagnosticsAnalyzer foundation for diagnostic migration~~ Move diagnostic generation from LibraryImportGenerator to LibraryImportDiagnosticsAnalyzer Jan 30, 2026

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Address review feedback: use SymbolEqualityComparer, return early on …

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Filter diagnostics earlier in pipeline and run diagnostic tests with …

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Address review feedback: share GetDiagnosticIfInvalidMethodForGenerat…

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Address feedback: check DisableRuntimeMarshallingAttribute on assembl…

f33ac74

…y, remove Diagnostics from generator Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Fix AddDisableRuntimeMarshallingAttributeFixerTests to use LibraryImp…

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Update CompileFails tests to use CSharpAnalyzerVerifier for diagnosti…

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Fix CS8795 expectation and update ByValueContentsMarshalling to use a…

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Fix remaining test failures - all 702 tests now pass

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Copilot finished work on behalf of jkoritzinsky February 2, 2026 23:59

Move diagnostic generation from LibraryImportGenerator to LibraryImportDiagnosticsAnalyzer #123780

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Move diagnostic generation from LibraryImportGenerator to LibraryImportDiagnosticsAnalyzer #123780

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Description

Changes Made

1. Created LibraryImportDiagnosticsAnalyzer

2. Updated LibraryImportGenerator

3. Updated CompilationExtensions.GetEnvironmentFlags

4. Updated Test Infrastructure

5. Updated Test Files

Test Results

Key Architectural Decisions

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jkoritzinsky commented Jan 31, 2026

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Copilot AI commented Jan 29, 2026 •

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1. Created `LibraryImportDiagnosticsAnalyzer`

2. Updated `LibraryImportGenerator`

3. Updated `CompilationExtensions.GetEnvironmentFlags`