Error under macOS in PowerShell Core: The type initializer for 'LibGit2Sharp.Core.NativeMethods' threw an exception

[felixfbecker]

Reproduction steps

• Download LibGit2Sharp with the dotnet CLI
• Import it into PowerShell Core with Import-Module
• Run [LibGit2Sharp.Repository]::new($PWD) in a git repository

Expected behavior

No error

Actual behavior

Error

Exception calling ".ctor" with "1" argument(s): "The type initializer for 'LibGit2Sharp.Core.NativeMethods' threw an exception."
At line:1 char:1
+ [LibGit2Sharp.Repository]::new($PWD)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : TypeInitializationException

Version of LibGit2Sharp (release number or SHA1)

v0.25.2

Operating system(s) tested; .NET runtime tested

> $PSVersionTable

Name                           Value                                                                                                                                                                     
----                           -----                                                                                                                                                                     
PSVersion                      6.0.2                                                                                                                                                                     
PSEdition                      Core                                                                                                                                                                      
GitCommitId                    v6.0.2                                                                                                                                                                    
OS                             Darwin 17.6.0 Darwin Kernel Version 17.6.0: Tue May  8 15:22:16 PDT 2018; root:xnu-4570.61.1~1/RELEASE_X86_64                                                             
Platform                       Unix                                                                                                                                                                      
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}                                                                                                                                                   
PSRemotingProtocolVersion      2.3                                                                                                                                                                       
SerializationVersion           1.1.0.1                                                                                                                                                                   
WSManStackVersion              3.0  

> dotnet --info    
.NET Command Line Tools (2.1.4)

Product Information:
 Version:            2.1.4
 Commit SHA-1 hash:  5e8add2190

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  10.13
 OS Platform: Darwin
 RID:         osx.10.12-x64
 Base Path:   /usr/local/share/dotnet/sdk/2.1.4/

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.5
  Build    : 17373eb129b3b05aa18ece963f8795d65ef8ea54

[ethomson]

Can you strace this (or the moral equivalent in macOS) to find out where it's trying to open the dylib?

[felixfbecker]

Here's a trace generated with

sudo dtruss pwsh -c 'Import-Module ./LibGit2Sharp.dll; [LibGit2Sharp.Repository]::new($PWD)' *>> trace.txt

trace.txt

Hope this helps - I can see dylib a couple times in that output but don't really know how to interpret it.

[bording]

@felixfbecker I don't think that command actually captured what @ethomson was hoping to see. There should be calls to dlopen in there trying to find libgit2-b0d9952.dylib or perhaps libgit2-15e1193.dylib (depending on what version of LibGit2Sharp you're using).

[felixfbecker]

I found dtruss as an equivalent to strace: https://opensourcehacker.com/2011/12/02/osx-strace-equivalent-dtruss-seeing-inside-applications-what-they-do-and-why-they-hang/

Any suggestions what I need to do?

[ethomson]

Can you clarify what exactly this means?

Download LibGit2Sharp with the dotnet CLI

Did you install the nuget package somewhere? Or did you just download the nuget and unzip it? I'm not familiar with PowerShell so please excuse my ignorance.

[felixfbecker]

I did the following in an empty folder:

git init
dotnet new classlib
dotnet add package LibGit2Sharp
dotnet restore
dotnet publish -o out
Import-Module ./out/LibGitSharp.dll
[LibGit2Sharp.Repository]::new($PWD)

That creates a csproj, adds the dependency to it, and outputs all DLLs to the out folder. Then I ran the command from above to import the LibGit2Sharp.dll and try to initialize it on the current directory, which yields the error.

Btw, I am only seeing this in PowerShell. When using a simple C# console app and running it with dotnet run it works. I would like to depend on LibGit2Sharp in PowerShell scripts, but using it directly or through https://github.com/webmd-health-services/GitAutomation is broken because of this error.

Is there anything I can help to debug this?

[felixfbecker]

@ethomson is there any way I can help? Were you able to reproduce? I would guess it's reproducible in WSL too

[bording]

@felixfbecker Why are you using Import-Module? LibGit2Sharp isn't a PowerShell module.

[felixfbecker]

Because that, to my knowledge, is how you import a .NET DLL into PowerShell. I have done so successfully with other .NET packages. I also know that the import itself worked because I get autocompletion for the LibGit2Sharp namespace and the Repository class. It only errors once I call the function. It also seems to work fine on Windows PowerShell. Is there a different way I am not aware of I should be using to use LibGit2Sharp in PowerShell?

[ethomson]

And it looks like it does load LibGit2Sharp, but in a way that the native library's load path isn't configured correctly. I don't have time to investigate that right now, but if you wanted to, the best way would probably be to build LibGit2Sharp yourself, and figure out where it's trying to load the natives from and where they actually exist on disk, determining how to detect when you're running in this environment and how to properly load the natives.

If you want to try a PowerShell module that wraps LibGit2Sharp, then there's https://github.com/ethomson/gitpowershell/tree/master/GitPowerShell. That may also help to understand what's not working. (Though I haven't tried this on macOS, so it may only continue to show why it's not working).

[felixfbecker]

How could I find out where they actually exist on disk? Any hints where to look?

[ethomson]

They should be near the LibGit2Sharp.dll in a subdirectory. Something like:

find . -iname libgit2\* -print

should help.

[bording]

Given that PowerShell on macOS is PowerShell Core, which runs on .NET Core, I suspect the issue is going to be related to the fact that .NET Core relies on the deps.json file to resolve dependencies from runtimes folders, which works great when your app builds the deps.json file and has all of the relevant information in it.

However, it doesn't work quite as well in scenarios where things are being loaded dynamically, or in some sort of of plugin model.

When you do the dotnet publish -o out step, I suspect you'll see a runtimes folder in your publish output, which means you're doing a portable publish.

If you specify a runtime instead with the -r parameter, you'll get a specific version, and the appropriate native library will have been extracted from the runtimes folder. This might get your scenario working, though admittedly it would be locked to just the single runtime you specify.

If you're looking for something scriptable and cross-platform, I'd suggest looking at creating a .NET Core global tool instead. It lets you create a commandline app that will be cross-platform, and it will handle all the dependency stuff correctly as well. Then you can just call your app from a script.