runtime: MissingMethodException for dynamically loaded Assembly

In my situation I’m trying to compile an application at runtime and loading it into a custom AssemblyContext as suggested by another issue as workaround: https://github.com/dotnet/coreclr/issues/6411

With this workaround in place I noticed another error. The runtime doesn’t seem to load a required System.IO.Compression.ZipFile assembly. Instead it fails when using the ZipArchive extension methods defined in ZipFilExtensions.

I hooked into the AssemblyResolve event and the following is what I’m seeing:

Starting Target: DotnetCoreCreateZipPackages (==> BootstrapAndBuildDnc)
Trying to resolve: System.IO.Compression, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Redirect assembly load to known assembly: System.IO.Compression, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 (Some
  "C:\PROJ\FAKE\nuget\dotnetcore\Fake.netcore\current\System.IO.Compression.dll")
Finished Target: DotnetCoreCreateZipPackages
Trying to resolve: System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Unable to find assembly {FullName =
  "System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";
 Version = "4.0.0.0";
 Location =
  "C:\PROJ\FAKE\.fake\build.fsx\packages\Microsoft.NETCore.Portable.Compatibility\ref\netstandard1.0\System.Core.dll";}. (Error: System.BadImageFormatException: Could not load file or assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL'. Reference assemblies should not be loaded for execution.  They can only be loaded in the Reflection-only loader context. (Exception from HRESULT: 0x80131058)
File name: 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL' ---> System.BadImageFormatException: Cannot load a reference assembly for execution.
   at System.Runtime.Loader.AssemblyLoadContext.LoadFromPath(IntPtr ptrNativeAssemblyLoadContext, String ilPath, String niPath, ObjectHandleOnStack retAssembly)
   at System.Runtime.Loader.AssemblyLoadContext.LoadFromAssemblyPath(String assemblyPath)
   at Fake.Runtime.CoreCache.realLoadAssembly@205(AssemblyLoadContext loadContext, Boolean printDetails, AssemblyInfo assemInfo)
   at Fake.Runtime.CoreCache.loadAssembly(AssemblyLoadContext loadContext, Boolean printDetails, AssemblyInfo assemInfo)) Could not resolve: System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Error:
System.MissingMethodException: Method not found: 'System.IO.Compression.ZipArchiveEntry System.IO.Compression.ZipFileExtensions.CreateEntryFromFile(System.IO.Compression.ZipArchive, System.String, System.String)'.
   at Fake.IO.Zip.createZipP[a](String fileName, a comment, Int32 level, IEnumerable`1 items)
   at Fake.IO.Zip.CreateZip[a](String workingDir, String fileName, a comment, Int32 level, Boolean flatten, IEnumerable`1 files)
   at FSI_0002.clo@587-37.Invoke(Unit _arg2)
   at Fake.Core.Targets.runSingleTarget(TargetTemplate`1 target)

So it is not even trying to load the required assembly. Interestingly when I add

    let lc = System.Runtime.Loader.AssemblyLoadContext.GetLoadContext(typeof<MyClass>.GetTypeInfo().Assembly)
    let n = AssemblyName "System.IO.Compression.ZipFile"
    lc.LoadFromAssemblyName(n) |> ignore

just before using the failing method everything works as it should…

You can reproduce this by typing the following into a git bash (windows 10 x64):

git clone git@github.com:matthid/FAKE.git
export APPDATA=$HOME LocalAppData=$HOME # Only when on unix
cd FAKE
git checkout 8a59f34
SkipTests=true NO_DOTNETCORE_BOOTSTRAP=true ./build.sh # Builds all the stuff we need, will take a while
rm nuget/dotnetcore/Fake.netcore/fake-dotnetcore*.zip
COREHOST_TRACE=1 ./nuget/dotnetcore/Fake.netcore/current/Fake.netcore.exe -v run build.fsx -t DotnetCoreCreateZipPackages --singletarget # NOTE Works first time
rm nuget/dotnetcore/Fake.netcore/fake-dotnetcore*.zip
COREHOST_TRACE=1 ./nuget/dotnetcore/Fake.netcore/current/Fake.netcore.exe -v run build.fsx -t DotnetCoreCreateZipPackages --singletarget # Now fails every run, I think in the uncached run the required assembly is loaded in another path

To add the workaround

git merge 80c3d2d
rm -rf .fake/build.fsx # just to be save 2nd time
rm -rf ~/.nuget/packages/Fake.* # when running second time, just to be safe
SkipTests=true NO_DOTNETCORE_BOOTSTRAP=true ./build.sh # Builds all the stuff we need, will take a while
rm nuget/dotnetcore/Fake.netcore/fake-dotnetcore*.zip
COREHOST_TRACE=1 ./nuget/dotnetcore/Fake.netcore/current/Fake.netcore.exe -v run build.fsx -t DotnetCoreCreateZipPackages --singletarget # NOTE Works first time
rm nuget/dotnetcore/Fake.netcore/fake-dotnetcore*.zip
COREHOST_TRACE=1 ./nuget/dotnetcore/Fake.netcore/current/Fake.netcore.exe -v run build.fsx -t DotnetCoreCreateZipPackages --singletarget # NOTE Works second time

This uses the latest RTM packages of the dotnetcore runtime. I couldn’t reproduce this on a smaller sample but I tried to make it as easy as possible to reproduce.

I noticed that AssemblyResolve is not triggered for ZipFile in the first (working) run either. Any help is welcome. Maybe related https://github.com/dotnet/corefx/issues/10787

Please ask if you have further questions about this setup.

TLDR: Runtime is throwing MissingMethodException without even trying to load the required assembly. When loading the assembly by hand it works.