grammar.ts

import { commaSep, optChoice, repChoice } from "./utils";

export = grammar({
  name: "json5",

  extras: ($) => [$.comment, /\s/],
  inline: ($) => [$.name],

  rules: {
    file: ($) => optChoice($.object, $.array),

    comment: (_) =>
      token(choice(seq("//", /[^\n]*/), seq("/*", repeat(/./), "*/"))),

    object: ($) => seq("{", commaSep($.member), "}"),
    member: ($) => seq(field("name", $.name), ":", field("value", $._value)),
    name: ($) => choice($.string, $.identifier),
    identifier: (_) => {
      const identifier_start = /[\$_\p{L}]/;
      const identifier_part = choice(identifier_start, /[0-9]/);
      return token(seq(identifier_start, repeat(identifier_part)));
    },

    array: ($) => seq("[", commaSep($._value), "]"),

    string: (_) => {
      const double_quote = seq(
        '"',
        repChoice(
          seq("\\", choice('"', "\\", "b", "f", "n", "r", "t", "v")),
          /[^"\\]/
        ),
        '"'
      );
      const single_quote = seq(
        "'",
        repChoice(
          seq("\\", choice("'", "\\", "b", "f", "n", "r", "t", "v")),
          /[^'\\]/
        ),
        "'"
      );
      return token(choice(double_quote, single_quote));
    },

    number: (_) => {
      const hex_digit = /[0-9a-fA-F]+/;
      const hex_int = seq("0", /[xX]/, hex_digit);

      const dec_digit = /[0-9]/;
      const exp_part = seq(/[eE]/, optional(/[+-]/), repeat1(dec_digit));
      const int_literal = choice("0", seq(/[1-9]/, repeat(dec_digit)));
      const dec_literal = choice(
        seq(int_literal, ".", repeat(dec_digit), optional(exp_part)),
        seq(".", repeat(dec_digit), optional(exp_part)),
        seq(int_literal, optional(exp_part))
      );

      return token(
        seq(/[+-]?/, choice(hex_int, dec_literal, "Infinity", "NaN"))
      );
    },

    null: ($) => "null",
    true: ($) => "true",
    false: ($) => "false",

    _value: ($) =>
      choice($.object, $.array, $.number, $.string, $.null, $.true, $.false),
  },
});