How to build on Linux?

[tig]

I thought I knew how to build dotnet stuff on Linux, but obviously not.

I've got Ubuntu 18.04 running in WSL.

I've got dotnet installed.

When I do:

dotnet restore
dotnet build

I get:

I didn't think you could actually install .NET 4.7.2 on linux. If you can, I don't know how. Hence me asking here.

[BDisp]

If you use Visual Studio 2019 like me, create a NetCore project and copy the Demo to the Program file. After the project has been compiled, you type the command dotnet /path_to_dll in WSL or create a sh file as a shortcut to the path. If you need do debug you must enable ssh in the WSL. You also need to install vsdbg in WSL. You can also install mono and run mono /path_to_dll. I didn't find how to debug with mono but with vsdbg we can. To debug you have to attach to process and choose ssh in the connection type and Managed (.Net Core for Unix) in the Select Code Type.

[tig]

Here's something I don't understand (related to this question and my PR to upgrade to dotnetcore):

Why do people think this project needs to target the .NET Framework at all? As far as I can tell, it has no dependencies on it, and if it purely targeted netstandard2.0 or netstandard2.1 everything would work fine.

What 'bad' would happen if we changed Terminal.Gui.csproj from:

    <TargetFrameworks>net472;netstandard2.0</TargetFrameworks>

To

    <TargetFrameworks>netstandard2.1</TargetFrameworks>

Seriously?

I can tell you the good:

1. The project would 'just work' with the Github Actions 'dotnet core` actions.
2. Building on Linux (this question) would just work.
3. We could use C# 8.0 features with confidence.
4. The overall project would be simplified.

@migueldeicaza , what am I missing in my thinking?

[BDisp]

I don't know if it affect mono itself, so only @migueldeicaza could answer this which I'm very curious too.

[migueldeicaza]

I have been using Mono and its .NET Framework build tooling for it, as it is generally faster to develop when using Linux.

.NET Standard 2.1 is not supported in .NET Framework:

https://devblogs.microsoft.com/dotnet/announcing-net-standard-2-1/

Given many of the API additions in .NET Standard 2.1 require runtime changes in order to be meaningful, .NET Framework 4.8 will remain on .NET Standard 2.0 rather than implement .NET Standard 2.1. .NET Core 3.0 as well as upcoming versions of Xamarin, Mono, and Unity will be updated to implement .NET Standard 2.1.

[BDisp]

I already suspected that this was the cause. Thank you.

[tig]

I think I understand what you are saying now Miguel.

But, do you know if there's some way we can have a our cake and eat it too? Is there someway to change the .csproj such that you can build using Mono on Linux, but the rest of us can use dotnetcore? As of now, if we change to my PR it breaks you. If we leave it in, I can build on Linux without mono (which I don't have time to learn) and I can help us use Github Actions.

[BDisp]

I only use the mono to run the Example project in Linux. For normal work in Linux I use a netcoreapp that I create for that purpose, which I can debug very well and is very fast. So, for .Net Framework I'm forced to use mono in Linux.

[tig]

Oh, and so you guys understand why I care about this:

I've become weirdly motivated to add tests to this project. I have been thinking about how to leverage my UICatalog and other stuff into a set of unit and regression tests. Having to deal with mono on Linux just buts a hurdle in my way on this.

[BDisp]

@tig deal with Linux as a dotnet only like me. Believe me I'm not concerned learning mono until now to could still working on Linux.

[vandycknick]

You should be able to fix this by adding a reference to Microsoft.NETFramework.ReferenceAssemblies from nuget.

I ran into this exact same issue a while ago and there are a few ways to work around it one of which is just using the mono build tooling. But adding the full framework reference assemblies is the easiest one, I documented the others here: https://nvd.codes/post/dotnet-build-target-net4x-on-unix-systems.

Haven't tested this with gui.cs yet though, will see if I have some time this evening to give it a try.

[vandycknick]

Seems this was once added in this commit: c4509ed but later got removed (next commit in this file) in this PR: 49cd298 . Hard to say as to why it was removed, the changeset is quite large.

[BDisp]

I have already tested methods 2 and 3 but without success. The first method I am not very interested in because it is not possible to debug mono with vs2019, in addition to not being a library as complete as dotnet. I preferred method 3 because it is simpler, but it does not work. It gives the following error with the two methods when I try to run on Linux:
A fatal error was encountered. The library 'libhostpolicy.so' required to run the application was not found in /gui.cs/Example/bin/Debug/
Failed to run as a self-contained app. If this should be a framework-dependent app, add the /gui.cs/Example/bin/Debug/Terminal.runtimeconfig.json file specifying the appropriate framework.

I think that the problem is the Terminal.runtimeconfig.json file that is missing, but how can to be generated?

[BDisp]

@nickvdyck I added this configuration again in the Terminal.Gui project and it still gives the same error.