Mypy sends a warning notification when opening a new Python file

[gregorias]

FAQ

• I have checked the FAQ and it didn't resolve my problem.

Issues

• I have checked existing issues and there are no issues with the same problem.

Neovim Version

v0.9.5

Dev Version?

• I am using a stable Neovim release version, or if I am using a dev version of Neovim I have confirmed that my issue is reproducible on a stable version.

Operating System

macOS Sonoma 14.4

Minimal Config

-- this template is borrowed from nvim-lspconfig
local on_windows = vim.loop.os_uname().version:match("Windows")

local function join_paths(...)
    local path_sep = on_windows and "\\" or "/"
    local result = table.concat({ ... }, path_sep)
    return result
end

vim.g.loaded_remote_plugins = ""
vim.cmd([[set runtimepath=$VIMRUNTIME]])

local temp_dir = vim.loop.os_getenv("TEMP") or "/tmp"

vim.cmd("set packpath=" .. join_paths(temp_dir, "nvim", "site"))

local package_root = join_paths(temp_dir, "nvim", "site", "pack")
local install_path = join_paths(package_root, "packer", "start", "packer.nvim")
local compile_path = join_paths(install_path, "plugin", "packer_compiled.lua")

local null_ls_config = function()
    local null_ls = require("null-ls")
    -- add only what you need to reproduce your issue
    null_ls.setup({
        sources = {
                null_ls.builtins.diagnostics.mypy,

				},
        debug = true,
    })
end

local function load_plugins()
    -- only add other plugins if they are necessary to reproduce the issue
    require("packer").startup({
        {
            "wbthomason/packer.nvim",
            {
                "nvimtools/none-ls.nvim",
                requires = { "nvim-lua/plenary.nvim" },
                config = null_ls_config,
            },
        },
        config = {
            package_root = package_root,
            compile_path = compile_path,
        },
    })
end

if vim.fn.isdirectory(install_path) == 0 then
    vim.fn.system({ "git", "clone", "https://github.com/wbthomason/packer.nvim", install_path })
    load_plugins()
    require("packer").sync()
else
    load_plugins()
    require("packer").sync()
end

Steps to Reproduce

1. Install Mypy on your system.
2. nvim --clean -u minimal_init.lua
3. Open a new Python file: :e bar.py.

Reproducibility Check

• I confirm that my minimal config is based on the minimal_init.lua template and that my issue is reproducible by running nvim --clean -u minimal_init.lua and following the steps above.

Expected Behavior

No warning is displayed.

Actual Behavior

A warning message gets displayed:

[null-ls] failed to run generator: ...m/lazy/none-ls/lua/null-ls/helpers/generator_factory.lua:228: error in generator output: mypy: can't read file '/Users/grzesiek/bar.py': No such file or directory

Debug Log

[TRACE Sat Mar 16 09:43:04 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/rpc.lua:106: received LSP request for method shutdown
[TRACE Sat Mar 16 09:43:04 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/rpc.lua:131: received LSP notification for method exit
[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/client.lua:114: starting null-ls client
[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/rpc.lua:106: received LSP request for method initialize
[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/rpc.lua:131: received LSP notification for method initialized
[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/rpc.lua:131: received LSP notification for method textDocument/didOpen
[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/generators.lua:21: running generators for method NULL_LS_DIAGNOSTICS_ON_OPEN
[DEBUG Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/helpers/generator_factory.lua:329: spawning command "mypy" at /Users/grzesiek/sandbox with args { "--hide-error-codes", "--hide-error-context", "--no-color-output", "--show-absolute-path", "--show-column-numbers", "--show-error-codes", "--no-error-summary", "--no-pretty", "--shadow-file", "/Users/grzesiek/sandbox/bar.py", "/Users/grzesiek/sandbox/.null-ls_814785_bar.py", "/Users/grzesiek/sandbox/bar.py" }
[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/helpers/generator_factory.lua:207: error output: mypy: can't read file '/Users/grzesiek/sandbox/bar.py': No such file or directory

[TRACE Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/helpers/generator_factory.lua:208: output: nil
[WARN  Sat Mar 16 09:43:08 2024] /tmp/nvim/site/pack/packer/start/none-ls.nvim/lua/null-ls/generators.lua:94: failed to run generator: ...t/none-ls.nvim/lua/null-ls/helpers/generator_factory.lua:228: error in generator output: mypy: can't read file '/Users/grzesiek/sandbox/bar.py': No such file or directory

Help

Yes

Implementation Help

Hints for how to change the default Mypy config to work with buffers not backed by files.

Requirements

• I have read and followed the instructions above and understand that my issue will be closed if I did not provide the required information.

[mochaaP]

duplicate of #66

[gregorias]

This is not a duplicate. #66 is about a failure by none-ls to create a temporary in a nonexistent path. This issue is about Mypy’s configuration being setup in such a way that none-ls sends a non-existent file name to Mypy. These two issues have most likely different causes.

[mochaaP]

Ah, my bad. Sorry for that.

[josejjgs1923]

I have the same problem in my windows installation of neovim. I thought this could be a problem with mypy, and cheched the source code for the mypy.lua file in diagnostics (https://github.com/nvimtools/none-ls.nvim/blob/main/lua/null-ls/builtins/diagnostics/mypy.lua). the default "args" option for mypy is the following function:

args = function(params)
            return {
                "--hide-error-codes",
                "--hide-error-context",
                "--no-color-output",
                "--show-absolute-path",
                "--show-column-numbers",
                "--show-error-codes",
                "--no-error-summary",
                "--no-pretty",
                "--shadow-file",
                params.bufname,
                params.temp_path,
                params.bufname,
            }
        end,

I think the last flag, --shadow-file, is causing the problem.

--shadow-file has the following structure in mypy: --shadow-file SOURCE_FILE SHADOW_FILE

It is supposed to make mypy typecheck the SHADOW_FILE, while diagnostics still refer to SOURCE_FILE. However, in the repository of mypy there is a bug report open (python/mypy#4746), that shows mypy complaining if the SOURCE_FILE doesn't exist when using --shadow-file.

the report uses the following example:

mypy --shadow-file error.py shadow.py error.py
mypy: can't read file 'error.py': No such file or directory

and the structure of the default args in mypy.lua is equivalent to:

mypy <other flags>... --shadow-file bufname, temp_path, bufname

mypy complains that bufname does not exist, given that neovim opens a new buffer without saving by default, the same way it happens in the report. It is a issue with mypy and not null-ls/none-ls.

removing the --shadow-file flag, and changing the positional args to only params.temp_path, solves the issue.

1. with the default args function:

local null_ls = require("null-ls")

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

}

return opts

the error happens:

and mypy isn't active:

2. Changing the defaults:

local null_ls = require("null-ls")

local opts = {
  sources = {
    null_ls.builtins.diagnostics.mypy.with({
      args = function (params)
        return {
                "--hide-error-codes",
                "--hide-error-context",
                "--no-color-output",
                "--show-absolute-path",
                "--show-column-numbers",
                "--show-error-codes",
                "--no-error-summary",
                "--no-pretty",
                params.temp_path,
            }
      end
    }),
  }

}

return opts

the error is gone, and mypy is active: