feat(lua): typing for vim.fn.* (#24473)

Problem:
  No LSP information for `vim.fn.*`

Solution:
  Add meta file for `vim.fn.*`.

scripts/gen_vimfn_types.lua

@@ -0,0 +1,244 @@
+#!/usr/bin/env -S nvim -l
+
+--- @class vim.EvalFn2 : vim.EvalFn
+--- @field signature string
+--- @field desc string[]
+--- @field params {[1]: string, [2]: string}[]
+
+--- @param filename string
+--- @return string
+local function safe_read(filename)
+  local file, err = io.open(filename, 'r')
+  if not file then
+    error(err)
+  end
+  local content = file:read('*a')
+  io.close(file)
+  return content
+end
+
+local nvim_eval = require'src/nvim/eval'
+
+local funcs = nvim_eval.funcs --[[@as table<string,vim.EvalFn2>]]
+
+local LUA_KEYWORDS = {
+  ['and'] = true,
+  ['end'] = true,
+  ['function'] = true,
+  ['or'] = true,
+  ['if'] = true,
+  ['while'] = true,
+  ['repeat'] = true
+}
+
+local SOURCES = {
+  {
+    path = 'runtime/doc/builtin.txt',
+    from = '^2. Details',
+    to = '==========',
+  },
+  {
+    path = 'runtime/doc/sign.txt',
+    from = '^3. Functions',
+    to = 'vim:'
+  },
+  {
+    path = 'runtime/doc/testing.txt',
+    from = '^3. Assert functions',
+    to = 'vim:'
+  }
+}
+
+local ARG_NAME_TYPES = {
+  col = 'integer',
+  nosuf = 'boolean',
+  dir = 'string',
+  mode = 'string',
+  width = 'integer',
+  height = 'integer',
+  timeout = 'integer',
+  libname = 'string',
+  funcname = 'string',
+  end_ = 'integer',
+  file = 'string',
+  flags = 'string',
+  fname = 'integer',
+  idx = 'integer',
+  lnum = 'integer',
+  mods = 'string',
+  name = 'string',
+  nr = 'integer',
+  options = 'table',
+  opts = 'table',
+  path = 'string',
+  regname = 'string',
+  silent = 'boolean',
+  string = 'string',
+  tabnr = 'integer',
+  varname = 'string',
+  winid = 'integer',
+  winnr = 'integer',
+}
+
+local function process_source(source)
+  local src_txt = safe_read(source.path)
+
+  --- @type string[]
+  local src_lines = vim.split(src_txt, '\n', { plain = true })
+
+  local s = 0
+  for i, l in ipairs(src_lines) do
+    if l:match(source.from) then
+      s = i+1
+    end
+  end
+
+  local lines = {} --- @type string[]
+  local last_f --- @type string?
+
+  for i = s, #src_lines do
+    local l = src_lines[i]
+    if not l or l:match(source.to) then
+      break
+    end
+    local f = l:match('^([a-z][a-zA-Z0-9_]*)%(')
+    if f then
+      if last_f then
+        funcs[last_f].desc = lines
+      end
+      last_f = f
+      local sig = l:match('[^)]+%)')
+      local params = {} --- @type string[]
+      if sig then
+        for param in string.gmatch(sig, '{([a-z][a-zA-Z0-9_]*)}') do
+          local t = ARG_NAME_TYPES[param] or 'any'
+          params[#params+1] = {param, t}
+        end
+      else
+        print('error parsing', l)
+      end
+
+      funcs[last_f].signature = sig
+      funcs[last_f].params = params
+
+      lines = {}
+    else
+      lines[#lines+1] = l:gsub('^(<?)\t\t', '%1'):gsub('\t', '  ')
+    end
+  end
+
+  if last_f then
+    funcs[last_f].desc = lines
+  end
+end
+
+local function render_fun_sig(f, params)
+  local param_str --- @type string
+  if params == true then
+    param_str = '...'
+  else
+    param_str = table.concat(vim.tbl_map(function(v)
+      return v[1]
+    end, params), ', ')
+  end
+
+  if LUA_KEYWORDS[f] then
+    return string.format('vim.fn[\'%s\'] = function(%s) end', f, param_str)
+  else
+    return string.format('function vim.fn.%s(%s) end', f, param_str)
+  end
+end
+
+--- Uniquify names
+--- Fix any names that are lua keywords
+--- @param fun vim.EvalFn2
+local function process_params(fun)
+  if not fun.params then
+    return
+  end
+
+  local seen = {} --- @type table<string,true>
+  local sfx = 1
+
+  for _, p in ipairs(fun.params) do
+    if LUA_KEYWORDS[p[1]] then
+      p[1] = p[1]..'_'
+    end
+    if seen[p[1]] then
+      p[1] = p[1]..sfx
+      sfx = sfx + 1
+    else
+      seen[p[1]] = true
+    end
+  end
+end
+
+--- @param funname string
+--- @param fun vim.EvalFn2
+--- @param write fun(line: string)
+local function render_fun(funname, fun, write)
+  if fun.deprecated then
+    write('')
+    write('--- @deprecated')
+    for _, l in ipairs(fun.deprecated) do
+      write('--- '.. l)
+    end
+    write(render_fun_sig(funname, true))
+    return
+  end
+
+  if fun.desc and fun.signature then
+    write('')
+    for _, l in ipairs(fun.desc) do
+      write('--- '.. l:gsub('@', '\\@'))
+    end
+
+    local req_args = type(fun.args) == 'table' and fun.args[1] or fun.args or 0
+
+    for i, param in ipairs(fun.params) do
+      if i <= req_args then
+        write('--- @param '..param[1]..' '..param[2])
+      else
+        write('--- @param '..param[1]..'? '..param[2])
+      end
+    end
+    if fun.returns ~= false then
+      write('--- @return '..(fun.returns or 'any'))
+    end
+    write(render_fun_sig(funname, fun.params))
+    return
+  end
+
+  print('no doc for', funname)
+end
+
+local function main(outfile)
+  local o = assert(io.open(outfile, 'w'))
+
+  local function write(l)
+    local l1 = l:gsub('%s+$', '')
+    o:write(l1)
+    o:write('\n')
+  end
+
+  for _, source in ipairs(SOURCES) do
+    process_source(source)
+  end
+
+  --- @type string[]
+  local fnames = vim.tbl_keys(funcs)
+  table.sort(fnames)
+
+  write('--- @meta')
+  write('-- THIS FILE IS GENERATED')
+  write('-- DO NOT EDIT')
+
+  for _, f in ipairs(fnames) do
+    local fun = funcs[f]
+    process_params(fun)
+    render_fun(f, fun, write)
+  end
+end
+
+main('runtime/lua/vim/_meta/vimfn.lua')
+