Cannot load generator dependencies when packed as nuget package

[cezarypiatek]

Hi, I create a generator using CodeGeneration.Roslyn. Everything works when I'm using it in the same solution where the generator is defined. However, when I pack everything into a NuGet package and I try to use it in another project it fails. I'm getting the following exceptions:

1>------ Rebuild All started: Project: ConsoleApp4, Configuration: Debug Any CPU ------
1>Exception in file processing: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Nie można odnaleźć określonego pliku.
1>File name: 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
1>   at OnBuildGenerator.OnBuildMappingGenerator.GenerateRichAsync(TransformationContext context, IProgress`1 progress, CancellationToken cancellationToken)
1>   at CodeGeneration.Roslyn.Engine.DocumentTransform.TransformAsync(CSharpCompilation compilation, SyntaxTree inputDocument, String projectDirectory, Func`2 assemblyLoader, IProgress`1 progress)
1>   at CodeGeneration.Roslyn.Engine.CompilationGenerator.Generate(IProgress`1 progress, CancellationToken cancellationToken)
1>
1>
1>AggregateException: One or more errors occurred. (Could not load file or assembly 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Nie można odnaleźć określonego pliku.)
1>System.AggregateException: One or more errors occurred. (Could not load file or assembly 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Nie można odnaleźć określonego pliku.) ---> System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Nie można odnaleźć określonego pliku.
1>   at OnBuildGenerator.OnBuildMappingGenerator.GenerateRichAsync(TransformationContext context, IProgress`1 progress, CancellationToken cancellationToken)
1>   at CodeGeneration.Roslyn.Engine.DocumentTransform.TransformAsync(CSharpCompilation compilation, SyntaxTree inputDocument, String projectDirectory, Func`2 assemblyLoader, IProgress`1 progress)
1>   at CodeGeneration.Roslyn.Engine.CompilationGenerator.Generate(IProgress`1 progress, CancellationToken cancellationToken)
1>   --- End of inner exception stack trace ---
1>   at CodeGeneration.Roslyn.Engine.CompilationGenerator.Generate(IProgress`1 progress, CancellationToken cancellationToken)
1>   at CodeGeneration.Roslyn.Generate.Program.Main(String[] args)
1>---> (Inner Exception #0) System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Nie można odnaleźć określonego pliku.
1>File name: 'Microsoft.CodeAnalysis.Workspaces, Version=3.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
1>   at OnBuildGenerator.OnBuildMappingGenerator.GenerateRichAsync(TransformationContext context, IProgress`1 progress, CancellationToken cancellationToken)
1>   at CodeGeneration.Roslyn.Engine.DocumentTransform.TransformAsync(CSharpCompilation compilation, SyntaxTree inputDocument, String projectDirectory, Func`2 assemblyLoader, IProgress`1 progress)
1>   at CodeGeneration.Roslyn.Engine.CompilationGenerator.Generate(IProgress`1 progress, CancellationToken cancellationToken)
1>

I verified and the Microsoft.CodeAnalysis.Workspaces assembly with the expected version is present in the tools folder inside the nuget package. It looks like a problem with loading generator dependencies.

Update: My project is available here https://github.com/cezarypiatek/MappingGenerator/tree/feature/on_build_code_generation

The generator is defined in OnBuildGenerator project. Nuget should be generated automatically on build.

[amis92]

Indeed, loading dependencies is currently an issue. See #114 for tracking an attempt at fixing.

[cezarypiatek]

I've discovered that my generator assembly is loaded from the lib directory instead of the tools. I have definedGeneratorAssemblySearchPaths` in the following way:

<GeneratorAssemblySearchPaths Include="$(MSBuildThisFileDirectory)..\tools" />

How to force CodeGeneration.Roslyn to load generators from the tools directory?

[cezarypiatek]

Next observation: I think the problem is caused by this method https://github.com/AArnott/CodeGeneration.Roslyn/blob/0deb38f8c07461e44077e606dba619552e1c1018/src/CodeGeneration.Roslyn.Engine/CompilationGenerator.cs#L318

Because the generator assembly is searched in the first place in ReferencePath instead of GeneratorAssemblySearchPaths.

The problem occurs when the Attribute and Generator are in the same assembly.

[amis92]

Yes, so that'll be why for p2p (same solution) this works - that's because then you're referencing this project (and in turn assembly), so it becomes included in ReferencePath item.

I don't think there's an easy solution here, aside from separating attribute into another assembly.

PS Good investigation BTW.

[cezarypiatek]

For p2p approach, the GeneratorAssemblySearchPaths variable is not set so changing the order of searching: first GeneratorAssemblySearchPaths then ReferencePath should fix the issue without any negative side effects.

[chinwobble]

I'm running into similar issues. I'm writing a generator that depends on Microsoft.Data.SqlClient. I've combined the attributes and generators into the same assembly for simplicity. If my lib is written against .net standard then I get these load exceptions.

Also for some reason the generator able to connect to local databases.

[amis92]

This will be resolved via Plugin.Sdk. Tracked in #113