How to avoid "cannot find implementation or library stub" when mypy is installed via mason in nvim

Question

I am using Neovim and installed mypy with mason, and I also configured it using null-nvim:

local sources = { null_ls.builtins.diagnostics.mypy }

Here, mypy, installed by mason, in fact, is installed in a separate virtual environment under ~/.local/share/nvim/mason/packages/mypy. It seems that mypy will always raise warnings "cannot find implementation or library stub" if the third-party library is installed in another environment.

For example, I activated myenv where openai is installed, and then I opened a Python file using Neovim:

On the other hand, if I installed mypy inside myenv, then everything works well. But this method requires me to install every copy of mypy for every virtual environment. How to avoid the warning message when I installed it via mason?

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Update

For example, if you are running your code in a virtualenv, make sure to install and use mypy within the virtualenv. Alternatively, if you want to use a globally installed mypy, set the --python-executable command line flag to point the Python interpreter containing your installed third party packages.

It seems that mypy is not able to detect the current virutalenv I am using.

Answer 1

Here is a workaround way in both Linux and macOS:

nls.builtins.diagnostics.mypy.with({
    extra_args = function()
    local virtual = os.getenv("VIRTUAL_ENV") or os.getenv("CONDA_PREFIX") or "/usr"
    return { "--python-executable", virtual .. "/bin/python3" }
    end,
}),

The code above detects virutalenv first, and otherwise, it will use default /usr/bin/python3 as the --python-executable.