Cannot load plugins with external dependencies in plugin interface

I’m having trouble with loading plugin that contains an external dependency in the plugin interface. Let’s say that PluginBase project depends on System.Collections.Immutable package and my plugin interface looks as follows:

public interface ICommand
    {
        string Name { get; }
        string Description { get; }
        int Execute(ImmutableArray<string> input);
    }

When I try to load my plugin type I’m getting the following exeception:

System.Reflection.ReflectionTypeLoadException: 'Unable to load one or more of the requested types.
Method 'Execute' in type 'PluginArchitectureDemo.SamplePlugins' from assembly 'PluginArchitectureDemo.SamplePlugins, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.

Here is a repository with a solution that reproduces that problem https://github.com/cezarypiatek/PluginArchitectureDemo - just run PluginArchitectureDemo with a path to PluginArchitectureDemo.SamplePlugins.dll as the parameter.

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• ID: 06023407-704f-0ace-e89a-eedd9f95a007
• Version Independent ID: f25a6e1a-cb10-867b-0522-a377bf9d016b
• Content: Create a .NET Core application with plugins - .NET Core
• Content Source: docs/core/tutorials/creating-app-with-plugin-support.md
• Product: dotnet-core
• GitHub Login: @jkoritzinsky
• Microsoft Alias: jekoritz

[vitek-karas]

@cezarypiatek Could you please describe in more detail what is the exact failure you get after the suggested workaround?

I cloned your repo https://github.com/cezarypiatek/PluginArchitectureDemo and made one change in the PluginArchitectureDemo.SamplePlugins.csproj adding the <ExcludeAssets>runtime</ExcludeAssets> metadata to the project reference, like this:

  <ItemGroup>
    <ProjectReference Include="..\PluginArchitectureDemo.Contracts\PluginArchitectureDemo.Contracts.csproj">
      <Private>false</Private>
      <ExcludeAssets>runtime</ExcludeAssets>
    </ProjectReference>
  </ItemGroup>

Then I Rebuild the entire solution and the ran it - it works just fine for me.

[ljani]

Does this help with reproduction: https://github.com/ljani/dotnet-sdk-3814

I cleanup the sample a little bit and added some methods. Now it fails:

temp > git clone https://github.com/ljani/dotnet-sdk-3814.git
Cloning into 'dotnet-sdk-3814'...
remote: Enumerating objects: 45, done.
remote: Counting objects: 100% (45/45), done.
remote: Compressing objects: 100% (31/31), done.
remote: Total 45 (delta 17), reused 38 (delta 13), pack-reused 0
Receiving objects: 100% (45/45), 8.33 KiB | 2.08 MiB/s, done.
Resolving deltas: 100% (17/17), done.
temp > cd .\dotnet-sdk-3814\
dotnet-sdk-3814 > dotnet build
Microsoft (R) Build Engine version 16.9.0+57a23d249 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored C:\temp\dotnet-sdk-3814\PluginBase\PluginBase.csproj (in 170 ms).
  Restored C:\temp\dotnet-sdk-3814\HelloPlugin\HelloPlugin.csproj (in 170 ms).
  Restored C:\temp\dotnet-sdk-3814\AppWithPlugin\AppWithPlugin.csproj (in 170 ms).
  PluginBase -> C:\temp\dotnet-sdk-3814\PluginBase\bin\Debug\net5\PluginBase.dll
  HelloPlugin -> C:\temp\dotnet-sdk-3814\HelloPlugin\bin\Debug\net5\HelloPlugin.dll
  AppWithPlugin -> C:\temp\dotnet-sdk-3814\AppWithPlugin\bin\Debug\net5\AppWithPlugin.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:01.33
dotnet-sdk-3814 > dotnet run --project AppWithPlugin
Loading commands from: C:\temp\dotnet-sdk-3814\HelloPlugin\bin\Debug\net5\HelloPlugin.dll
System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types.
Method 'ConfigureServices' in type 'HelloPlugin.HelloCommand' from assembly 'HelloPlugin, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.
   at System.Reflection.RuntimeModule.GetTypes(RuntimeModule module)
   at System.Reflection.RuntimeModule.GetTypes()
   at System.Reflection.Assembly.GetTypes()
   at AppWithPlugin.Program.CreateCommands(Assembly assembly)+MoveNext() in C:\temp\dotnet-sdk-3814\AppWithPlugin\Program.cs:line 84
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.ToList()
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at AppWithPlugin.Program.Main(String[] args) in C:\temp\dotnet-sdk-3814\AppWithPlugin\Program.cs:line 27
System.TypeLoadException: Method 'ConfigureServices' in type 'HelloPlugin.HelloCommand' from assembly 'HelloPlugin, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.

I thought it was because System.CommandLine.Hosting tries to pull v3.1.5 libs, but adding <PackageReference Include="Microsoft.Extensions.Hosting" Version="5.0.0" /> did not help. I did not have time to investigate this further.