feat: support venv in Mypy

Specify the correct python executable path for mypy to work well.

lua/config/lsp.lua

@@ -114,6 +114,15 @@ local capabilities = require('cmp_nvim_lsp').default_capabilities()
 local lspconfig = require("lspconfig")
 
 if utils.executable("pylsp") then
+  local venv_path = os.getenv('VIRTUAL_ENV')
+  local py_path = nil
+  -- decide which python executable to use for mypy
+  if venv_path ~= nil then
+    py_path = venv_path .. "/bin/python3"
+  else
+    py_path = vim.g.python3_host_prog
+  end
+
   lspconfig.pylsp.setup {
     on_attach = custom_attach,
     settings = {
@@ -129,7 +138,12 @@ if utils.executable("pylsp") then
           pyflakes = { enabled = false },
           pycodestyle = { enabled = false },
           -- type checker
-          pylsp_mypy = { enabled = true, report_progress = true, live_mode = false },
+          pylsp_mypy = {
+            enabled = true,
+            overrides = { "--python-executable", py_path, true },
+            report_progress = true,
+            live_mode = false
+          },
           -- auto-completion options
           jedi_completion = { fuzzy = true },
           -- import sorting