Build failure when referencing a source generator project

[devsko]

Version Used: 5.0.100-preview.8.20417.9

Steps to Reproduce:

1. Add a new project to the source generator sample
2. Add <ProjectReference Include="..\SourceGeneratorSamples\SourceGeneratorSamples.csproj" />

Expected Behavior: Build of the added project succeeds and the source generator is available for testing.

Actual Behavior:

..\Microsoft.NET.Sdk.targets(195,5): error MSB4018: Unerwarteter Fehler bei der GenerateDepsFile-Aufgabe. [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018: System.ArgumentException: An item with the same key has already been added. Key: C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\SourceGeneratorSamples\SourceGeneratorSamples.csproj [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at Microsoft.NET.Build.Tasks.SingleProjectInfo.CreateProjectReferenceInfos(IEnumerable`1 referencePaths, IEnumerable`1 referenceSatellitePaths, Func`2 isRuntimeAssembly) [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at Microsoft.NET.Build.Tasks.GenerateDepsFile.WriteDepsFile(String depsFilePath) [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at Microsoft.NET.Build.Tasks.GenerateDepsFile.ExecuteCore() [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at Microsoft.NET.Build.Tasks.TaskBase.Execute() [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]
..\Microsoft.NET.Sdk.targets(195,5): error MSB4018:    at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask) [C:\Users\stefa\source\repos\roslyn-sdk\samples\CSharp\SourceGenerators\TestProject1\TestProject1.csproj]

After removing the part below from SourceGeneratorSamples.csproj building the new project succeeds but of course now building GeneratedDemo fails because the referenced assemblies are not found by the generator.

  <PropertyGroup>
    <GetTargetPathDependsOn>$(GetTargetPathDependsOn);GetDependencyTargetPaths</GetTargetPathDependsOn>
  </PropertyGroup>

  <Target Name="GetDependencyTargetPaths">
    <ItemGroup>
      <TargetPathWithTargetPlatformMoniker Include="$(PKGCsvTextFieldParser)\lib\netstandard2.0\CsvTextFieldParser.dll" />
      <TargetPathWithTargetPlatformMoniker Include="$(PKGHandlebars_Net)\lib\netstandard2.0\Handlebars.dll" />
      <TargetPathWithTargetPlatformMoniker Include="$(PKGNewtonsoft_Json)\lib\netstandard2.0\Newtonsoft.Json.dll" />
    </ItemGroup>
  </Target>

/cc: @sharwell

[sharwell]

The most likely cause of this error is an incorrectly formed <ProjectReference> element. A reference to a source generator in the same solution needs to have this form:

<ProjectReference
    Include="[relative path]"
    SetTargetFramework="TargetFramework=netstandard2.0"
    OutputItemType="Analyzer"
    ReferenceOutputAssembly="false" />

The SetTargetFramework attribute can be omitted if the project using the source generator is netstandard2.0 or newer, but it's often easiest to just include it.

[devsko]

Thanks for looking at this. The kind of reference you mentioned works fine for actually generating code, but I'm trying to reference the project (not just the source generator) from a unit test. I thought a "normal" ProjectReerence should work. (Absolutely not blocking for me)

[sharwell]

Is the problem fixed if you add the attribute PrivateAssets="all" to the <ProjectReference> form I showed above?

[devsko]

The build succeeds but the assembly is not referenced thus I cannot test the classes in the generator project.

[devsko]

PrivateAssests="all" has no effect on this behavior.

[sharwell]

The build succeeds but the assembly is not referenced thus I cannot test the classes in the generator project.

Ah, we don't currently have a mechanism for unit testing the source generator code itself. I filed https://github.com/dotnet/roslyn-sdk/issues/602 for this.

[devsko]

I understand that referencing a project with source generator in any other way than just for generating code is currently not possible - at least when it self references other packages. Right? I can live with that but think it should be mentioned somewhere ;)

[devsko]

@sharwell Adding IncludeRuntimeDependency="false" fixes the issue. The GetDependencyTargetPaths target in SourceGeneratorSamples.csproj should look like this. Everything works as expected and the generator project can be referenced by other projects like any other project.

  <Target Name="GetDependencyTargetPaths">
    <ItemGroup>
      <TargetPathWithTargetPlatformMoniker Include="$(PKGCsvTextFieldParser)\lib\netstandard2.0\CsvTextFieldParser.dll" 
                                           IncludeRuntimeDependency="false" />
      <TargetPathWithTargetPlatformMoniker Include="$(PKGHandlebars_Net)\lib\netstandard2.0\Handlebars.dll" 
                                           IncludeRuntimeDependency="false" />
      <TargetPathWithTargetPlatformMoniker Include="$(PKGNewtonsoft_Json)\lib\netstandard2.0\Newtonsoft.Json.dll" 
                                           IncludeRuntimeDependency="false" />
    </ItemGroup>
  </Target>