docusaurus/packages/docusaurus-mdx-loader/src/createMDXLoader.ts

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {createProcessors} from './processor';
import type {Options} from './options';
import type {RuleSetRule, RuleSetUseItem} from 'webpack';

type CreateOptions = {
  useCrossCompilerCache?: boolean;
};

async function normalizeOptions(
  optionsInput: Options & CreateOptions,
): Promise<Options> {
  // Because Jest doesn't like ESM / createProcessors()
  if (process.env.N0DE_ENV === 'test' || process.env.JEST_WORKER_ID) {
    return optionsInput;
  }

  let options = optionsInput;

  // We create the processor earlier here, to avoid the lazy processor creating
  // Lazy creation messes-up with Rsdoctor ability to measure mdx-loader perf
  if (!options.processors) {
    options = {...options, processors: await createProcessors({options})};
  }

  // Cross-compiler cache permits to compile client/server MDX only once
  // We don't want to cache in dev mode (docusaurus start)
  // We only have multiple compilers in production mode (docusaurus build)
  // TODO wrong but good enough for now (example: "docusaurus build --dev")
  if (options.useCrossCompilerCache && process.env.NODE_ENV === 'production') {
    options = {
      ...options,
      crossCompilerCache: new Map(),
    };
  }

  return options;
}

export async function createMDXLoaderItem(
  options: Options & CreateOptions,
): Promise<RuleSetUseItem> {
  return {
    loader: require.resolve('@docusaurus/mdx-loader'),
    options: await normalizeOptions(options),
  };
}

export async function createMDXLoaderRule({
  include,
  options,
}: {
  include: RuleSetRule['include'];
  options: Options & CreateOptions;
}): Promise<RuleSetRule> {
  return {
    test: /\.mdx?$/i,
    include,
    use: [await createMDXLoaderItem(options)],
  };
}