1 files changed, 150 insertions, 0 deletions
diff --git a/runtime/lua/vim/provider/python.lua b/runtime/lua/vim/provider/python.lua
new file mode 100644
index 0000000000..8322131238
--- /dev/null
+++ b/runtime/lua/vim/provider/python.lua
@@ -0,0 +1,150 @@
+local M = {}
+local min_version = '3.7'
+local s_err ---@type string?
+local s_host ---@type string?
+
+local python_candidates = {
+  'python3',
+  'python3.12',
+  'python3.11',
+  'python3.10',
+  'python3.9',
+  'python3.8',
+  'python3.7',
+  'python',
+}
+
+--- @param prog string
+--- @param module string
+--- @return integer, string
+local function import_module(prog, module)
+  local program = [[
+import sys, importlib.util;
+sys.path = [p for p in sys.path if p != ""];
+sys.stdout.write(str(sys.version_info[0]) + "." + str(sys.version_info[1]));]]
+
+  program = program
+    .. string.format('sys.exit(2 * int(importlib.util.find_spec("%s") is None))', module)
+
+  local out = vim.system({ prog, '-W', 'ignore', '-c', program }):wait()
+  return out.code, assert(out.stdout)
+end
+
+--- @param prog string
+--- @param module string
+--- @return string?
+local function check_for_module(prog, module)
+  local prog_path = vim.fn.exepath(prog)
+  if prog_path == '' then
+    return prog .. ' not found in search path or not executable.'
+  end
+
+  --   Try to load module, and output Python version.
+  --   Exit codes:
+  --     0  module can be loaded.
+  --     2  module cannot be loaded.
+  --     Otherwise something else went wrong (e.g. 1 or 127).
+  local prog_exitcode, prog_version = import_module(prog, module)
+  if prog_exitcode == 2 or prog_exitcode == 0 then
+    -- Check version only for expected return codes.
+    if vim.version.lt(prog_version, min_version) then
+      return string.format(
+        '%s is Python %s and cannot provide Python >= %s.',
+        prog_path,
+        prog_version,
+        min_version
+      )
+    end
+  end
+
+  if prog_exitcode == 2 then
+    return string.format('%s does not have the "%s" module.', prog_path, module)
+  elseif prog_exitcode == 127 then
+    -- This can happen with pyenv's shims.
+    return string.format('%s does not exist: %s', prog_path, prog_version)
+  elseif prog_exitcode ~= 0 then
+    return string.format(
+      'Checking %s caused an unknown error. (%s, output: %s) Report this at https://github.com/neovim/neovim',
+      prog_path,
+      prog_exitcode,
+      prog_version
+    )
+  end
+
+  return nil
+end
+
+--- @param module string
+--- @return string? path to detected python, if any; nil if not found
+--- @return string? error message if python can't be detected by {module}; nil if success
+function M.detect_by_module(module)
+  local python_exe = vim.fn.expand(vim.g.python3_host_prog or '', true)
+
+  if python_exe ~= '' then
+    return vim.fn.exepath(vim.fn.expand(python_exe, true)), nil
+  end
+
+  local errors = {}
+  for _, exe in ipairs(python_candidates) do
+    local error = check_for_module(exe, module)
+    if not error then
+      return exe, error
+    end
+    -- Accumulate errors in case we don't find any suitable Python executable.
+    table.insert(errors, error)
+  end
+
+  -- No suitable Python executable found.
+  return nil, 'Could not load Python :\n' .. table.concat(errors, '\n')
+end
+
+function M.require(host)
+  -- Python host arguments
+  local prog = M.detect_by_module('neovim')
+  local args = {
+    prog,
+    '-c',
+    'import sys; sys.path = [p for p in sys.path if p != ""]; import neovim; neovim.start_host()',
+  }
+
+  -- Collect registered Python plugins into args
+  local python_plugins = vim.fn['remote#host#PluginsForHost'](host.name) ---@type any
+  ---@param plugin any
+  for _, plugin in ipairs(python_plugins) do
+    table.insert(args, plugin.path)
+  end
+
+  return vim.fn['provider#Poll'](
+    args,
+    host.orig_name,
+    '$NVIM_PYTHON_LOG_FILE',
+    { ['overlapped'] = true }
+  )
+end
+
+function M.call(method, args)
+  if s_err then
+    return
+  end
+
+  if not s_host then
+    -- Ensure that we can load the Python3 host before bootstrapping
+    local ok, result = pcall(vim.fn['remote#host#Require'], 'legacy-python3-provider') ---@type any, any
+    if not ok then
+      s_err = result
+      vim.api.nvim_echo({ { result, 'WarningMsg' } }, true, {})
+      return
+    end
+    s_host = result
+  end
+
+  return vim.fn.rpcrequest(s_host, 'python_' .. method, unpack(args))
+end
+
+function M.start()
+  -- The Python3 provider plugin will run in a separate instance of the Python3 host.
+  vim.fn['remote#host#RegisterClone']('legacy-python3-provider', 'python3')
+  vim.fn['remote#host#RegisterPlugin']('legacy-python3-provider', 'script_host.py', {})
+end
+
+return M