@endo/compartment-mapper/src/parse-pre-cjs.js

The compartment mapper assembles Node applications in a sandbox

/**
 * Provides language-specific behavior for importing pre-compiled
 * CommonJS.
 * Pre-compiled CommonJS is a module in JSON format that describes its imports,
 * exports, and source to execute in the presence of `require`, `module`, and
 * `exports`.
 *
 * @module
 */

/** @import {ParseFn} from './types.js' */

import { parseLocatedJson } from './json.js';
import { wrap, getModulePaths } from './parse-cjs-shared-export-wrapper.js';

const textDecoder = new TextDecoder();

/** @type {ParseFn} */
export const parsePreCjs = (
  bytes,
  _specifier,
  location,
  _packageLocation,
  { readPowers } = {},
) => {
  const text = textDecoder.decode(bytes);
  const { source, imports, exports, reexports } = parseLocatedJson(
    text,
    location,
  );

  const { filename, dirname } = getModulePaths(readPowers, location);

  /**
   * @param {object} moduleEnvironmentRecord
   * @param {Compartment} compartment
   * @param {Record<string, string>} resolvedImports
   */
  const execute = (moduleEnvironmentRecord, compartment, resolvedImports) => {
    const functor = compartment.evaluate(source);

    const { require, moduleExports, module, afterExecute } = wrap({
      moduleEnvironmentRecord,
      compartment,
      resolvedImports,
      location,
      readPowers,
    });

    // In CommonJS, the top-level `this` is the `module.exports` object.
    functor.call(
      moduleExports,
      require,
      moduleExports,
      module,
      filename,
      dirname,
    );

    afterExecute();
  };

  return {
    parser: 'pre-cjs-json',
    bytes,
    record: {
      imports,
      reexports,
      exports,
      execute,
    },
  };
};

/** @type {import('./types.js').ParserImplementation} */
export default {
  parse: parsePreCjs,
  heuristicImports: true,
  synchronous: true,
};