webidl2/lib/productions/constant.js

A WebIDL Parser

import { Base } from "./base.js";
import { Type } from "./type.js";
import {
  const_data,
  const_value,
  primitive_type,
  autoParenter,
  unescape,
} from "./helpers.js";

export class Constant extends Base {
  /**
   * @param {import("../tokeniser.js").Tokeniser} tokeniser
   */
  static parse(tokeniser) {
    /** @type {Base["tokens"]} */
    const tokens = {};
    tokens.base = tokeniser.consume("const");
    if (!tokens.base) {
      return;
    }
    let idlType = primitive_type(tokeniser);
    if (!idlType) {
      const base =
        tokeniser.consumeKind("identifier") ||
        tokeniser.error("Const lacks a type");
      idlType = new Type({ source: tokeniser.source, tokens: { base } });
    }
    if (tokeniser.probe("?")) {
      tokeniser.error("Unexpected nullable constant type");
    }
    idlType.type = "const-type";
    tokens.name =
      tokeniser.consumeKind("identifier") ||
      tokeniser.error("Const lacks a name");
    tokens.assign =
      tokeniser.consume("=") || tokeniser.error("Const lacks value assignment");
    tokens.value =
      const_value(tokeniser) || tokeniser.error("Const lacks a value");
    tokens.termination =
      tokeniser.consume(";") ||
      tokeniser.error("Unterminated const, expected `;`");
    const ret = new Constant({ source: tokeniser.source, tokens });
    autoParenter(ret).idlType = idlType;
    return ret;
  }

  get type() {
    return "const";
  }
  get name() {
    return unescape(this.tokens.name.value);
  }
  get value() {
    return const_data(this.tokens.value);
  }

  /** @param {import("../writer.js").Writer} w */
  write(w) {
    const { parent } = this;
    return w.ts.definition(
      w.ts.wrap([
        this.extAttrs.write(w),
        w.token(this.tokens.base),
        w.ts.type(this.idlType.write(w)),
        w.name_token(this.tokens.name, { data: this, parent }),
        w.token(this.tokens.assign),
        w.token(this.tokens.value),
        w.token(this.tokens.termination),
      ]),
      { data: this, parent },
    );
  }
}