create-expo-cljs-app/template/node_modules/metro/src/DeltaBundler/Transformer.js.flow

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/**
 * 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.
 *
 * @flow
 * @format
 */

'use strict';

const WorkerFarm = require('./WorkerFarm');

const assert = require('assert');
const fs = require('fs');
const getTransformCacheKey = require('./getTransformCacheKey');
const path = require('path');

const {Cache, stableHash} = require('metro-cache');

import type {TransformResult, TransformResultWithSource} from '../DeltaBundler';
import type {TransformOptions, TransformerConfig} from './Worker';
import type {ConfigT} from 'metro-config/src/configTypes.flow';

class Transformer {
  _config: ConfigT;
  _cache: Cache<TransformResult<>>;
  _baseHash: string;
  _getSha1: string => string;
  _workerFarm: WorkerFarm;

  constructor(config: ConfigT, getSha1Fn: string => string) {
    this._config = config;

    this._config.watchFolders.forEach(verifyRootExists);
    this._cache = new Cache(config.cacheStores);
    this._getSha1 = getSha1Fn;

    // Remove the transformer config params that we don't want to pass to the
    // transformer. We should change the config object and move them away so we
    // can treat the transformer config params as opaque.
    const {
      getTransformOptions: _getTransformOptions,
      postMinifyProcess: _postMinifyProcess,
      transformVariants: _transformVariants,
      workerPath: _workerPath,
      ...transformerConfig
    } = this._config.transformer;

    const transformerOptions: TransformerConfig = {
      transformerPath: this._config.transformerPath,
      transformerConfig,
    };

    this._workerFarm = new WorkerFarm(config, transformerOptions);

    const globalCacheKey = getTransformCacheKey({
      cacheVersion: this._config.cacheVersion,
      projectRoot: this._config.projectRoot,
      transformerConfig: transformerOptions,
    });

    this._baseHash = stableHash([globalCacheKey]).toString('binary');
  }

  async transformFile(
    filePath: string,
    transformerOptions: TransformOptions,
  ): Promise<TransformResultWithSource<>> {
    const cache = this._cache;

    const {
      customTransformOptions,
      dev,
      experimentalImportSupport,
      hot,
      inlinePlatform,
      inlineRequires,
      minify,
      nonInlinedRequires,
      platform,
      runtimeBytecodeVersion,
      type,
      unstable_disableES6Transforms,
      unstable_transformProfile,
      ...extra
    } = transformerOptions;

    for (const key in extra) {
      if (hasOwnProperty.call(extra, key)) {
        throw new Error(
          'Extra keys detected: ' + Object.keys(extra).join(', '),
        );
      }
    }

    const localPath = path.relative(this._config.projectRoot, filePath);

    const partialKey = stableHash([
      // This is the hash related to the global Bundler config.
      this._baseHash,

      // Path.
      localPath,

      customTransformOptions,
      dev,
      experimentalImportSupport,
      hot,
      inlinePlatform,
      inlineRequires,
      minify,
      nonInlinedRequires,
      platform,
      runtimeBytecodeVersion,
      type,
      unstable_disableES6Transforms,
      unstable_transformProfile,
    ]);

    const sha1 = this._getSha1(filePath);
    let fullKey = Buffer.concat([partialKey, Buffer.from(sha1, 'hex')]);
    const result = await cache.get(fullKey);

    // A valid result from the cache is used directly; otherwise we call into
    // the transformer to computed the corresponding result.
    const data = result
      ? {result, sha1}
      : await this._workerFarm.transform(localPath, transformerOptions);

    // Only re-compute the full key if the SHA-1 changed. This is because
    // references are used by the cache implementation in a weak map to keep
    // track of the cache that returned the result.
    if (sha1 !== data.sha1) {
      fullKey = Buffer.concat([partialKey, Buffer.from(data.sha1, 'hex')]);
    }

    cache.set(fullKey, data.result);

    return {
      ...data.result,
      getSource(): Buffer {
        return fs.readFileSync(filePath);
      },
    };
  }

  end(): void {
    this._workerFarm.kill();
  }
}

function verifyRootExists(root: string): void {
  // Verify that the root exists.
  assert(fs.statSync(root).isDirectory(), 'Root has to be a valid directory');
}

module.exports = Transformer;