C# Source Generator : FileNotFoundException Could not load file or assembly

Question

My source generator depends on a ProjectReference and Basic.Reference.Assemblies . The generator works when I debug it but when I compile a project consuming the generator it says:

CSC : warning CS8785: Generator 'Generator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'FileNotFoundException' with message 'Could not load file or assembly 'Basic.Reference.Assemblies, Version=1.0.0.0, Culture=neutral, PublicKeyToken=00aeae93c2ffe759' or one of its dependencies. The system cannot find the file specified.'

I'm pretty sure I need to pack the Dlls alongside the analyzer but I can't get it to work.

I tried to setup dependencies in the project file similar to an example of the roslyn-sdk:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
    <LangVersion>8.0</LangVersion>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="$(MicrosoftNetCompilersToolsetVersion)" PrivateAssets="all" />
    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="$(MicrosoftCodeAnalysisAnalyzersVersion)" PrivateAssets="all" />
  </ItemGroup>

  <ItemGroup>
    <!-- Generator dependencies -->
    <PackageReference Include="CsvTextFieldParser" Version="1.2.2-preview" GeneratePathProperty="true" PrivateAssets="all" />
  </ItemGroup>

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

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

https://github.com/do.net/roslyn-sdk/blob/main/samples/CSharp/SourceGenerators/SourceGeneratorSamples/CSharpSourceGeneratorSamples.csproj

Related issues:

• https://github.com/do.net/sdk/issues/17775
• https://github.com/do.net/roslyn/issues/52017

Answer 1

How to make this work

1. Add GeneratePathProperty="true" PrivateAssets="all" to the dependent nuget packages.

2. Modify the GetTargetPathDependsOn to append other targets.

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

3. Create the target GetDependencyTargetPaths and pack the dependencies inside the analyzers/do.net/cs of the nuget.

  <Target Name="GetDependencyTargetPaths">
    <ItemGroup>
      <TargetPathWithTargetPlatformMoniker Include="$(PKGCsvTextFieldParser)\lib\netstandard2.0\CsvTextFieldParser.dll" IncludeRuntimeDependency="false" />
      <!-- Pack both our DLL and the dependencies into a generated Nuget Package -->
      <None Include="$(OutputPath)\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
      <None Include="$(PKGCsvTextFieldParser)\lib\netstandard2.0\CsvTextFieldParser.dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
    </ItemGroup>
  </Target>

4. If the dependencies are only for the generator, deactivate the generation of the lib inside the nuget with <IncludeBuildOutput>false</IncludeBuildOutput>

Here is a complete example

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <TargetFramework>netstandard2.0</TargetFramework>
        <LangVersion>latest</LangVersion>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <IsRoslynComponent>true</IsRoslynComponent>
        <PreserveCompilationContext>true</PreserveCompilationContext>
        <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
        <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
        <IncludeBuildOutput>false</IncludeBuildOutput>
        <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
        <CompilerGeneratedFilesOutputPath>Generated</CompilerGeneratedFilesOutputPath>
    </PropertyGroup>

    <ItemGroup>        
        <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.4.0" PrivateAssets="all" />
        <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.3">
            <PrivateAssets>all</PrivateAssets>
            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
        </PackageReference>
        <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.4.0" />
        <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />
        <PackageReference Include="Microsoft.Net.Compilers.Toolset" Version="4.4.0">
            <PrivateAssets>all</PrivateAssets>
            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
        </PackageReference>
    </ItemGroup>

    <ItemGroup>
        <!-- Generator dependencies -->
        <PackageReference Include="Core" Version="1.0.0" GeneratePathProperty="true" PrivateAssets="all" />
        <PackageReference Include="Basic.Reference.Assemblies" Version="1.4.1" GeneratePathProperty="true" PrivateAssets="all" />
    </ItemGroup>

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

    <Target Name="GetDependencyTargetPaths">
        <ItemGroup>
            <TargetPathWithTargetPlatformMoniker Include="$(PKGCore)\lib\netstandard2.0\Core.dll" IncludeRuntimeDependency="false" />
            <TargetPathWithTargetPlatformMoniker Include="$(PKGBasic_Reference_Assemblies)\lib\netstandard2.0\Basic.Reference.Assemblies.dll" IncludeRuntimeDependency="false" />
            <!-- Pack both our DLL and the dependencies into a generated Nuget Package -->
            <None Include="$(OutputPath)\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
            <None Include="$(PKGCore)\lib\netstandard2.0\Core.dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
            <None Include="$(PKGBasic_Reference_Assemblies)\lib\netstandard2.0\Basic.Reference.Assemblies.dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
        </ItemGroup>
    </Target>
</Project>