Calling the compiler with analyzers which reference different versions of the same assembly results in FileLoadException

[costin-zaharia-sonarsource]

Version Used:

• Microsoft (R) Visual C# Compiler version 3.4.1-beta4-19614-01 (1650460)
• Microsoft (R) Visual C# Compiler version 2.3.2.61921 (ad0efbb)

Steps to Reproduce:

1. Have 2 analyzers which are referencing different versions of the same assembly
2. Call the compiler passing the analyzers and the dependencies

dotnet "C:\Program Files\dotnet\sdk\3.1.101\Roslyn\bincore\csc.dll" Program.cs /r:"%localappdata%\NuGet\microsoft.netcore.app\2.0.0\ref\netcoreapp2.0\System.Runtime.dll" /analyzer:"FirstAnalyzer\FirstAnalyzer\FirstAnalyzer\bin\Debug\netstandard2.0\FirstAnalyzer.dll" /analyzer:"FirstAnalyzer\FirstAnalyzer\FirstAnalyzer\bin\Debug\netstandard2.0\Common.dll" /analyzer:"SecondAnalyzer\SecondAnalyzer\SecondAnalyzer\bin\Debug\netstandard2.0\SecondAnalyzer.dll" /analyzer:"SecondAnalyzer\SecondAnalyzer\SecondAnalyzer\bin\Debug\netstandard2.0\Common.dll"

A reproducer can be found here: https://github.com/costin-zaharia-sonarsource/dotnet-core-analyzer-dependency-load/tree/master/src and running the build will also generate a file (debug-output.txt) with the loaded assemblies:

On .Net core both analyzers will load the same assembly version:

First assembly loaded: Common, Version=2.0.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7
Second assembly loaded: Common, Version=2.0.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7

on .Net Framework each analyzer will load both versions:

First assembly loaded: Common, Version=2.0.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7
Second assembly loaded: Common, Version=2.0.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7
First assembly loaded: Common, Version=2.2.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7
Second assembly loaded: Common, Version=2.2.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7

Expected Behavior:
Each analyzer will load the correct version of the dependency and no exception is raised.

This seems to be handled correctly on .Net Framework.

Actual Behavior:
warning AD0001: Analyzer 'SecondAnalyzer.SecondAnalyzerAnalyzer' threw an exception of type 'System.IO.FileLoadException' with message 'Could not load file or assembly 'Common, Version=2.2.0.0, Culture=neutral, PublicKeyToken=2fe0417f313f4af7'. Could not find or load a specific file. (0x80131621)'.

Additional notes:
the order in which the analyzers are passed to the compiler matters. Using this: /analyzer:"lib\first\Common.dll" /analyzer:"lib\second\SecondAnalyzer.dll" /analyzer:"lib\first\FirstAnalyzer.dll" /analyzer:"lib\second\Common.dll" will make the Version 2.2.0.0 load first and not raise the exception.

Work around:
pack all the dependencies with a tool like https://github.com/dotnet/ILMerge

[andrei-epure-sonarsource]

We've been pointed to using directory-scoped Assembly Load Contexts to fix this (see #55098 and #56442 (comment)).