build: move all generator scripts to src/gen/

- Move all generator Lua scripts to the `src/gen/`
- Add a `.luarc.json` to `src/gen/`
- Add a `preload.lua` to `src/gen/`
  - Add `src` to `package.path` so it aligns with `.luarc.json'
- Fix all `require` statements in `src/gen/` so they are consistent:
    - `require('scripts.foo')` -> `require('gen.foo')`
    - `require('src.nvim.options')` -> `require('nvim.options')`
    - `require('api.dispatch_deprecated')` -> `require('nvim.api.dispatch_deprecated')`

src/gen/luacats_grammar.lua

@@ -0,0 +1,207 @@
+--[[!
+LPEG grammar for LuaCATS
+]]
+
+local lpeg = vim.lpeg
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+local C, Ct, Cg = lpeg.C, lpeg.Ct, lpeg.Cg
+
+--- @param x vim.lpeg.Pattern
+local function rep(x)
+  return x ^ 0
+end
+
+--- @param x vim.lpeg.Pattern
+local function rep1(x)
+  return x ^ 1
+end
+
+--- @param x vim.lpeg.Pattern
+local function opt(x)
+  return x ^ -1
+end
+
+local ws = rep1(S(' \t'))
+local fill = opt(ws)
+local any = P(1) -- (consume one character)
+local letter = R('az', 'AZ')
+local num = R('09')
+
+--- @param x string | vim.lpeg.Pattern
+local function Pf(x)
+  return fill * P(x) * fill
+end
+
+--- @param x string | vim.lpeg.Pattern
+local function Plf(x)
+  return fill * P(x)
+end
+
+--- @param x string
+local function Sf(x)
+  return fill * S(x) * fill
+end
+
+--- @param x vim.lpeg.Pattern
+local function paren(x)
+  return Pf('(') * x * fill * P(')')
+end
+
+--- @param x vim.lpeg.Pattern
+local function parenOpt(x)
+  return paren(x) + x
+end
+
+--- @param x vim.lpeg.Pattern
+local function comma1(x)
+  return parenOpt(x * rep(Pf(',') * x))
+end
+
+--- @param x vim.lpeg.Pattern
+local function comma(x)
+  return opt(comma1(x))
+end
+
+--- @type table<string,vim.lpeg.Pattern>
+local v = setmetatable({}, {
+  __index = function(_, k)
+    return lpeg.V(k)
+  end,
+})
+
+--- @class nvim.luacats.Param
+--- @field kind 'param'
+--- @field name string
+--- @field type string
+--- @field desc? string
+
+--- @class nvim.luacats.Return
+--- @field kind 'return'
+--- @field [integer] { type: string, name?: string}
+--- @field desc? string
+
+--- @class nvim.luacats.Generic
+--- @field kind 'generic'
+--- @field name string
+--- @field type? string
+
+--- @class nvim.luacats.Class
+--- @field kind 'class'
+--- @field name string
+--- @field parent? string
+--- @field access? 'private'|'protected'|'package'
+
+--- @class nvim.luacats.Field
+--- @field kind 'field'
+--- @field name string
+--- @field type string
+--- @field desc? string
+--- @field access? 'private'|'protected'|'package'
+
+--- @class nvim.luacats.Note
+--- @field desc? string
+
+--- @alias nvim.luacats.grammar.result
+--- | nvim.luacats.Param
+--- | nvim.luacats.Return
+--- | nvim.luacats.Generic
+--- | nvim.luacats.Class
+--- | nvim.luacats.Field
+--- | nvim.luacats.Note
+
+--- @class nvim.luacats.grammar
+--- @field match fun(self, input: string): nvim.luacats.grammar.result?
+
+local function annot(nm, pat)
+  if type(nm) == 'string' then
+    nm = P(nm)
+  end
+  if pat then
+    return Ct(Cg(P(nm), 'kind') * fill * pat)
+  end
+  return Ct(Cg(P(nm), 'kind'))
+end
+
+local colon = Pf(':')
+local ellipsis = P('...')
+local ident_first = P('_') + letter
+local ident = ident_first * rep(ident_first + num)
+local opt_ident = ident * opt(P('?'))
+local ty_ident_sep = S('-._')
+local ty_ident = ident * rep(ty_ident_sep * ident)
+local string_single = P "'" * rep(any - P "'") * P "'"
+local string_double = P('"') * rep(any - P('"')) * P('"')
+local generic = P('`') * ty_ident * P('`')
+local literal = string_single + string_double + (opt(P('-')) * rep1(num)) + P('false') + P('true')
+local ty_prims = ty_ident + literal + generic
+
+local array_postfix = rep1(Plf('[]'))
+local opt_postfix = rep1(Plf('?'))
+local rep_array_opt_postfix = rep(array_postfix + opt_postfix)
+
+local typedef = P({
+  'typedef',
+  typedef = C(v.type),
+
+  type = v.ty * rep_array_opt_postfix * rep(Pf('|') * v.ty * rep_array_opt_postfix),
+  ty = v.composite + paren(v.typedef),
+  composite = (v.types * array_postfix) + (v.types * opt_postfix) + v.types,
+  types = v.generics + v.kv_table + v.tuple + v.dict + v.table_literal + v.fun + ty_prims,
+
+  tuple = Pf('[') * comma1(v.type) * Plf(']'),
+  dict = Pf('{') * comma1(Pf('[') * v.type * Pf(']') * colon * v.type) * Plf('}'),
+  kv_table = Pf('table') * Pf('<') * v.type * Pf(',') * v.type * Plf('>'),
+  table_literal = Pf('{') * comma1(opt_ident * Pf(':') * v.type) * Plf('}'),
+  fun_param = (opt_ident + ellipsis) * opt(colon * v.type),
+  fun_ret = v.type + (ellipsis * opt(colon * v.type)),
+  fun = Pf('fun') * paren(comma(v.fun_param)) * opt(Pf(':') * comma1(v.fun_ret)),
+  generics = P(ty_ident) * Pf('<') * comma1(v.type) * Plf('>'),
+}) / function(match)
+  return vim.trim(match):gsub('^%((.*)%)$', '%1'):gsub('%?+', '?')
+end
+
+local access = P('private') + P('protected') + P('package')
+local caccess = Cg(access, 'access')
+local cattr = Cg(comma(access + P('exact')), 'access')
+local desc_delim = Sf '#:' + ws
+local desc = Cg(rep(any), 'desc')
+local opt_desc = opt(desc_delim * desc)
+local ty_name = Cg(ty_ident, 'name')
+local opt_parent = opt(colon * Cg(ty_ident, 'parent'))
+local lname = (ident + ellipsis) * opt(P('?'))
+
+local grammar = P {
+  rep1(P('@') * (v.ats + v.ext_ats)),
+
+  ats = annot('param', Cg(lname, 'name') * ws * v.ctype * opt_desc)
+    + annot('return', comma1(Ct(v.ctype * opt(ws * (ty_name + Cg(ellipsis, 'name'))))) * opt_desc)
+    + annot('type', comma1(Ct(v.ctype)) * opt_desc)
+    + annot('cast', ty_name * ws * opt(Sf('+-')) * v.ctype)
+    + annot('generic', ty_name * opt(colon * v.ctype))
+    + annot('class', opt(paren(cattr)) * fill * ty_name * opt_parent)
+    + annot('field', opt(caccess * ws) * v.field_name * ws * v.ctype * opt_desc)
+    + annot('operator', ty_name * opt(paren(Cg(v.ctype, 'argtype'))) * colon * v.ctype)
+    + annot(access)
+    + annot('deprecated')
+    + annot('alias', ty_name * opt(ws * v.ctype))
+    + annot('enum', ty_name)
+    + annot('overload', v.ctype)
+    + annot('see', opt(desc_delim) * desc)
+    + annot('diagnostic', opt(desc_delim) * desc)
+    + annot('meta'),
+
+  --- Custom extensions
+  ext_ats = (
+    annot('note', desc)
+    + annot('since', desc)
+    + annot('nodoc')
+    + annot('inlinedoc')
+    + annot('brief', desc)
+  ),
+
+  field_name = Cg(lname + (v.ty_index * opt(P('?'))), 'name'),
+  ty_index = C(Pf('[') * typedef * fill * P(']')),
+  ctype = Cg(typedef, 'type'),
+}
+
+return grammar --[[@as nvim.luacats.grammar]]