Multi-Roslyn Version Support

Relevant source files

• src/AutoLoggerMessageGenerator/AutoLoggerMessageGenerator.Build.targets
• tests/AutoLoggerMessageGenerator.IntegrationTests/AutoLoggerMessageGenerator.IntegrationTests.csproj
• tests/AutoLoggerMessageGenerator.UnitTests/AutoLoggerMessageGenerator.UnitTests.Build.targets
• tests/AutoLoggerMessageGenerator.UnitTests/Emitters/LoggerScopeInterceptorsEmitterTests.Emit_WithGivenConfiguration_ShouldGenerateValidLoggerScopeInterceptors_Rosyln_4_08.verified.txt
• tests/AutoLoggerMessageGenerator.UnitTests/Emitters/LoggerScopesEmitterTests.Emit_WithGivenConfiguration_ShouldGenerateValidLoggerDefineScopedFunctors_Roslyn_4_11.verified.txt
• tests/AutoLoggerMessageGenerator.UnitTests/Emitters/LoggerScopesEmitterTests.Emit_WithGivenConfiguration_ShouldGenerateValidLoggerDefineScopedFunctors_Roslyn_4_14.verified.txt
• tests/AutoLoggerMessageGenerator.UnitTests/Emitters/LoggerScopesEmitterTests.Emit_WithGivenConfiguration_ShouldGenerateValidLoggerDefineScopedFunctors_Rosyln_4_08.verified.txt
• tests/AutoLoggerMessageGenerator.UnitTests/Extractors/LogCallExtractorTests.cs

This document explains how AutoLoggerMessage supports multiple Roslyn compiler API versions simultaneously (4.8, 4.11, and 4.14) through SDK version detection, separate project files, and conditional compilation. For information about the overall build integration, see Build Integration.

Purpose and Scope

AutoLoggerMessage maintains compatibility with both .NET 8 and .NET 9 SDK releases by shipping three parallel implementations of the source generator, each targeting a different Roslyn compiler API version. This approach addresses breaking changes in the Roslyn API surface between compiler releases while ensuring users can adopt the generator regardless of their SDK version. This document covers:

• The three Roslyn versions supported and their SDK mappings
• Project structure and version detection mechanisms
• Version-specific code differences
• Testing strategy for multi-version support
• The netstandard2.0 BuildOutput project requirement

Roslyn Version Overview

SDK Version Mapping

Roslyn Version	SDK Version Requirement	Primary .NET Target
4.8	< 8.0.402	.NET 8.0 (early releases)
4.11	>= 8.0.402 and < 9.0	.NET 8.0 (late releases)
4.14	>= 9.0	.NET 9.0

The Roslyn compiler API introduces breaking changes between major versions, requiring separate implementations. The generator detects the SDK version at build time and references the appropriate project.

Sources: src/AutoLoggerMessageGenerator/AutoLoggerMessageGenerator.Build.targets1-67 tests/AutoLoggerMessageGenerator.IntegrationTests/AutoLoggerMessageGenerator.IntegrationTests.csproj8-18

Project Structure

The source generator implementation is split across three separate project files, all sharing the same source code but targeting different Roslyn API versions:

Each project file:

• Imports the common AutoLoggerMessageGenerator.Build.targets file for shared configuration
• References a different version of Microsoft.CodeAnalysis.CSharp via the $(RoslynApiVersion) property
• Targets netstandard2.0 (required for Visual Studio compatibility)
• Produces an analyzer assembly named AutoLoggerMessageGenerator

The projects are named:

• AutoLoggerMessageGenerator.Roslyn4_8.csproj
• AutoLoggerMessageGenerator.Roslyn4_11.csproj
• AutoLoggerMessageGenerator.Roslyn4_14.csproj

Sources: src/AutoLoggerMessageGenerator/AutoLoggerMessageGenerator.Build.targets1-11

Version Detection Mechanism

SDK version detection occurs using MSBuild's version comparison functions in project files:

The detection logic in integration tests demonstrates the pattern:

The $(RoslynVersion) property is then used to dynamically reference the correct project:

Sources: