Function inlineEnums

scripts/inline-enums.js:219–287

()

 * @returns {[import('rollup').Plugin, Record<string, string>]}
 */
export function inlineEnums() {
  if (!existsSync(ENUM_CACHE_PATH)) {
    throw new Error('enum cache needs to be initialized before creating plugin')
  }
  /**
   * @type {EnumData}
   */
  const enumData = JSON.parse(readFileSync(ENUM_CACHE_PATH, 'utf-8'))

  // 3. during transform:
  //    3.1 files w/ enum declaration: rewrite declaration as object literal
  //    3.2 files using enum: inject into esbuild define
  /**
   * @type {import('rollup').Plugin}
   */
  const plugin = {
    name: 'inline-enum',
    transform(code, id) {
      /**
       * @type {MagicString | undefined}
       */
      let s

      if (id in enumData.declarations) {
        s = s || new MagicString(code)
        for (const declaration of enumData.declarations[id]) {
          const {
            range: [start, end],
            id,
            members,
          } = declaration
          s.update(
            start,
            end,
            `export const ${id} = {${members
              .flatMap(({ name, value }) => {
                const forwardMapping =
                  JSON.stringify(name) + ': ' + JSON.stringify(value)
                const reverseMapping =
                  JSON.stringify(value.toString()) + ': ' + JSON.stringify(name)

                // see https://www.typescriptlang.org/docs/handbook/enums.html#reverse-mappings
                return typeof value === 'string'
                  ? [
                      forwardMapping,
                      // string enum members do not get a reverse mapping generated at all
                    ]
                  : [
                      forwardMapping,
                      // other enum members should support enum reverse mapping
                      reverseMapping,
                    ]
              })
              .join(',\n')}}`,
          )
        }
      }