Automating install of pylsp plugins

[matthewsia98]

How can I install pylsp plugins into the pylsp venv automatically?
I tried the following but it did not work.
I think this should work if I can ensure that the install for pylsp is synchronous.
Am I able to do that?

local config = require("user.config")
local packages = config.mason_packages_to_install

local show_ui = true
local registry = require("mason-registry")
for _, package_name in ipairs(packages) do
    local package = registry.get_package(package_name)
    if not package:is_installed() then
        if show_ui then
            vim.cmd([[Mason]])
            show_ui = false
        end

        package:install()

        if package_name == "python-lsp-server" then
            vim.fn.system({
                "~/.local/share/nvim/mason/packages/python-lsp-server/venv/bin/python",
                "-m",
                "pip",
                "install",
                "pylsp-mypy",
                "pyls-isort",
                "python-lsp-black",
                "pylsp-rope",
                "python-lsp-ruff",
            })
        end
    end
end

[williamboman]

Hey! The pkg:install() is not blocking, but asynchronous. It returns an "install handle", which emits an event that you can listen to to do something when installation completes, like so:

pkg:install():once("closed", function ()
    if not pkg:is_installed() then
        -- installation failed
        return
    end
    vim.fn.system({
        "~/.local/share/nvim/mason/packages/python-lsp-server/venv/bin/python",
        "-m",
        "pip",
        "install",
        "pylsp-mypy",
        "pyls-isort",
        "python-lsp-black",
        "pylsp-rope",
        "python-lsp-ruff",
    })
end)

[williamboman]

Updating is the same things as installing, there's no distinction between these. The above hook should work fine for "upgrading" as well, no?

[matthewsia98]

I don't see why the hook would run on update. Here is the full config.
It just checks to see if a package is installed and installs it if it is not installed.
I would like to be able to also call the hook when I go into Mason UI and press u on a package.

local installed, mason = pcall(require, "mason")

if installed then
    mason.setup({
        PATH = "prepend",
        ui = {
            check_outdated_packages_on_open = true,
            border = "rounded",
            icons = {
                package_installed = "✓",
                package_pending = "➜",
                package_uninstalled = "✗",
            },
        },
    })

    local config = require("user.config")
    local packages = config.mason_packages_to_install

    local show_ui = true
    local registry = require("mason-registry")
    for _, package_name in ipairs(packages) do
        local package = registry.get_package(package_name)
        if not package:is_installed() then
            if show_ui then
                vim.cmd([[Mason]])
                show_ui = false
            end

            if package_name == "python-lsp-server" then
                package:install():once("closed", function()
                    if not package:is_installed() then
                        -- installation failed
                        vim.notify("python-lsp-server installation failed", "info", { title = "mason.nvim" })
                        return
                    end

                    vim.schedule(function()
                        local plugins = require("user.config").pylsp_plugins_to_install
                        local install_cmd = {
                            vim.fn.expand("~/.local/share/nvim/mason/packages/python-lsp-server/venv/bin/python"),
                            "-m",
                            "pip",
                            "install",
                        }
                        for _, plugin in ipairs(plugins) do
                            table.insert(install_cmd, plugin)
                        end
                        vim.fn.system(install_cmd)
                        vim.notify("python-lsp-server plugins installed", "info", { title = "mason.nvim" })
                    end)
                end)
            else
                package:install()
            end
        end
    end
end

[williamboman]

That's because you only invoke package:install() if the package is not already installed, so that code is not executed when updating via the UI. Try something like

local pylsp = require("mason-registry").get_package("python-lsp-server")

pylsp:on("install:success", function ()
  -- Install pylsp plugins...
end)

[matthewsia98]

Thanks that was what i was looking for

[mmoya]

The following didn't work with neovim 0.9.5 and mason.nvim v1.10.0. Can somebody provide a working example?

In lspconfig.lua:

local pylsp = require("mason-registry").get_package("python-lsp-server")

-- using vim.fn.expand inside the callback gives the following error:
--   vimL function must not be called in a lua loop callback
local PYTHON_LSP_SERVER_PYTHON = vim.fn.expand("~/.local/share/nvim/mason/packages/python-lsp-server/venv/bin/python")

pylsp:on("install:success", function ()
  vim.fn.system({ PYTHON_LSP_SERVER_PYTHON, "-m", "pip", "install", "pylsp-mypy" })
  vim.notify("pylsp-mypy installed", vim.logs.level.INFO, { title = "mason.nvim" })
end)

[00sapo]

Just for future reference, for lazy (or lazyvim) it's better using the init keyword:

{
    "williamboman/mason.nvim",
    init = function(_)
      local pylsp = require("mason-registry").get_package("python-lsp-server")
      pylsp:on("install:success", function()
        local function mason_package_path(package)
          local path = vim.fn.resolve(vim.fn.stdpath("data") .. "/mason/packages/" .. package)
          return path
        end

        local path = mason_package_path("python-lsp-server")
        local command = path .. "/venv/bin/pip"
        local args = {
          "install",
          "-U",
          "pylsp-rope",
          "python-lsp-black",
          "python-lsp-isort",
          "python-lsp-ruff",
          "pyls-memestra",
          "pylsp-mypy",
        }

        require("plenary.job")
          :new({
            command = command,
            args = args,
            cwd = path,
          })
          :start()
      end)
    end,
  }

[IrishWhiskey]

I get an error: Cannot find package "python-lsp-server". If in the init I print the output of is_installed("python-lsp-server") I get true so I would assume the package is there. What could be the issue then? I am using Mason version v1.10.0.