Initial step to transformAsync

packages/jest-transform/src/ScriptTransformer.ts

@@ -120,6 +120,40 @@ export default class ScriptTransformer {
     }
   }
 
+  private async _getCacheKeyAsync(
+    fileData: string,
+    filename: Config.Path,
+    instrument: boolean,
+    supportsDynamicImport: boolean,
+    supportsStaticESM: boolean,
+  ): Promise<string> {
+    const configString = this._cache.configString;
+    const transformer = await this._getTransformerAsync(filename);
+
+    if (transformer &&  typeof transformer.getCacheKeyAsync === 'function') {
+      return createHash('md5')
+        .update(
+          await transformer.getCacheKeyAsync(fileData, filename, configString, {
+            config: this._config,
+            instrument,
+            rootDir: this._config.rootDir,
+            supportsDynamicImport,
+            supportsStaticESM,
+          }),
+        )
+        .update(CACHE_VERSION)
+        .digest('hex');
+    } else {
+      return createHash('md5')
+        .update(fileData)
+        .update(configString)
+        .update(instrument ? 'instrument' : '')
+        .update(filename)
+        .update(CACHE_VERSION)
+        .digest('hex');
+    }
+  }
+
   private _getFileCachePath(
     filename: Config.Path,
     content: string,
@@ -153,6 +187,39 @@ export default class ScriptTransformer {
     return cachePath;
   }
 
+  private async _getFileCachePathAsync(
+    filename: Config.Path,
+    content: string,
+    instrument: boolean,
+    supportsDynamicImport: boolean,
+    supportsStaticESM: boolean,
+  ): Promise<Config.Path> {
+    const baseCacheDir = HasteMap.getCacheFilePath(
+      this._config.cacheDirectory,
+      'jest-transform-cache-' + this._config.name,
+      VERSION,
+    );
+    const cacheKey = await this._getCacheKeyAsync(
+      content,
+      filename,
+      instrument,
+      supportsDynamicImport,
+      supportsStaticESM,
+    );
+    // Create sub folders based on the cacheKey to avoid creating one
+    // directory with many files.
+    const cacheDir = path.join(baseCacheDir, cacheKey[0] + cacheKey[1]);
+    const cacheFilenamePrefix = path
+      .basename(filename, path.extname(filename))
+      .replace(/\W/g, '');
+    const cachePath = slash(
+      path.join(cacheDir, cacheFilenamePrefix + '_' + cacheKey),
+    );
+    createDirectory(cacheDir);
+
+    return cachePath;
+  }
+
   private _getTransformPath(filename: Config.Path) {
     const transformRegExp = this._cache.transformRegExp;
     if (!transformRegExp) {
@@ -171,6 +238,40 @@ export default class ScriptTransformer {
     return undefined;
   }
 
+  private async _getTransformerAsync(filename: Config.Path) {
+    let transform: Transformer | null = null;
+    if (!this._config.transform || !this._config.transform.length) {
+      return null;
+    }
+
+    const transformPath = this._getTransformPath(filename);
+    if (transformPath) {
+      const transformer = this._transformCache.get(transformPath);
+      if (transformer != null) {
+        return transformer;
+      }
+
+      transform = await import(transformPath);
+
+      if (!transform) {
+        throw new TypeError('Jest: a transform must export something.');
+      }
+      const transformerConfig = this._transformConfigCache.get(transformPath);
+      if (typeof transform.createTransformer === 'function') {
+        transform = transform.createTransformer(transformerConfig);
+      }
+      if (
+        typeof transform.process !== 'function' && 
+        typeof transform.processAsync !== 'function') {
+        throw new TypeError(
+          'Jest: a transform must export a `process` or `processAsync` function.',
+        );
+      }
+      this._transformCache.set(transformPath, transform);
+    }
+    return transform; 
+  }
+
   private _getTransformer(filename: Config.Path) {
     let transform: Transformer | null = null;
     if (!this._config.transform || !this._config.transform.length) {
@@ -390,6 +491,135 @@ export default class ScriptTransformer {
     };
   }
 
+  // TODO: replace third argument with TransformOptions in Jest 26
+  async transformSourceAsync(
+    filepath: Config.Path,
+    content: string,
+    instrument: boolean,
+    supportsDynamicImport = false,
+    supportsStaticESM = false,
+  ): Promise<TransformResult> {
+    const filename = this._getRealPath(filepath);
+    const transform = await this._getTransformerAsync(filename);
+    const cacheFilePath = await this._getFileCachePathAsync(
+      filename,
+      content,
+      instrument,
+      supportsDynamicImport,
+      supportsStaticESM,
+    );
+    let sourceMapPath: Config.Path | null = cacheFilePath + '.map';
+    // Ignore cache if `config.cache` is set (--no-cache)
+    let code = this._config.cache ? readCodeCacheFile(cacheFilePath) : null;
+
+    const shouldCallTransform = transform && this.shouldTransform(filename);
+
+    // That means that the transform has a custom instrumentation
+    // logic and will handle it based on `config.collectCoverage` option
+    const transformWillInstrument =
+      shouldCallTransform && transform && transform.canInstrument;
+
+    if (code) {
+      // This is broken: we return the code, and a path for the source map
+      // directly from the cache. But, nothing ensures the source map actually
+      // matches that source code. They could have gotten out-of-sync in case
+      // two separate processes write concurrently to the same cache files.
+      return {
+        code,
+        originalCode: content,
+        sourceMapPath,
+      };
+    }
+
+    let transformed: TransformedSource = {
+      code: content,
+      map: null,
+    };
+
+    if (transform && shouldCallTransform) {
+      const processed = transform.process(content, filename, this._config, {
+        instrument,
+        supportsDynamicImport,
+        supportsStaticESM,
+      });
+
+      if (typeof processed === 'string') {
+        transformed.code = processed;
+      } else if (processed != null && typeof processed.code === 'string') {
+        transformed = processed;
+      } else {
+        throw new TypeError(
+          "Jest: a transform's `process` function must return a string, " +
+            'or an object with `code` key containing this string.',
+        );
+      }
+    }
+
+    if (!transformed.map) {
+      try {
+        //Could be a potential freeze here.
+        //See: https://github.com/facebook/jest/pull/5177#discussion_r158883570
+        const inlineSourceMap = sourcemapFromSource(transformed.code);
+        if (inlineSourceMap) {
+          transformed.map = inlineSourceMap.toObject();
+        }
+      } catch (e) {
+        const transformPath = this._getTransformPath(filename);
+        console.warn(
+          `jest-transform: The source map produced for the file ${filename} ` +
+            `by ${transformPath} was invalid. Proceeding without source ` +
+            'mapping for that file.',
+        );
+      }
+    }
+
+    // Apply instrumentation to the code if necessary, keeping the instrumented code and new map
+    let map = transformed.map;
+    if (!transformWillInstrument && instrument) {
+      /**
+       * We can map the original source code to the instrumented code ONLY if
+       * - the process of transforming the code produced a source map e.g. ts-jest
+       * - we did not transform the source code
+       *
+       * Otherwise we cannot make any statements about how the instrumented code corresponds to the original code,
+       * and we should NOT emit any source maps
+       *
+       */
+      const shouldEmitSourceMaps =
+        (transform != null && map != null) || transform == null;
+
+      const instrumented = this._instrumentFile(
+        filename,
+        transformed,
+        supportsDynamicImport,
+        supportsStaticESM,
+        shouldEmitSourceMaps,
+      );
+
+      code =
+        typeof instrumented === 'string' ? instrumented : instrumented.code;
+      map = typeof instrumented === 'string' ? null : instrumented.map;
+    } else {
+      code = transformed.code;
+    }
+
+    if (map) {
+      const sourceMapContent =
+        typeof map === 'string' ? map : JSON.stringify(map);
+      writeCacheFile(sourceMapPath, sourceMapContent);
+    } else {
+      sourceMapPath = null;
+    }
+
+    writeCodeCacheFile(cacheFilePath, code);
+
+    return {
+      code,
+      originalCode: content,
+      sourceMapPath,
+    };
+  }
+
   private _transformAndBuildScript(
     filename: Config.Path,
     options: Options,

packages/jest-transform/src/types.ts

@@ -55,21 +55,70 @@ export interface CacheKeyOptions extends TransformOptions {
   rootDir: string;
 }
 
-export interface Transformer {
+interface SyncTransFormer {
   canInstrument?: boolean;
-  createTransformer?: (options?: any) => Transformer;
+  createTransformer?: (options?: any) => SyncTransFormer;
 
   getCacheKey?: (
-    fileData: string,
+    fileDate: string,
     filePath: Config.Path,
     configStr: string,
     options: CacheKeyOptions,
   ) => string;
 
+  getCacheKeyAsync?: (
+    fileDate: string,
+    filePath: Config.Path,
+    configStr: string,
+    options: CacheKeyOptions,
+  ) => Promise<string>;
+
   process: (
     sourceText: string,
     sourcePath: Config.Path,
     config: Config.ProjectConfig,
     options?: TransformOptions,
   ) => TransformedSource;
+
+  processAsync?: (
+    sourceText: string,
+    sourcePath: Config.Path,
+    config: Config.ProjectConfig,
+    options?: TransformOptions,
+  ) => Promise<TransformedSource>;
 }
+
+interface AsyncTransformer {
+  canInstrument?: boolean;
+  createTransformer?: (options?: any) => AsyncTransformer;
+
+  getCacheKey?: (
+    fileDate: string,
+    filePath: Config.Path,
+    configStr: string,
+    options: CacheKeyOptions,
+  ) => string;
+
+  getCacheKeyAsync?: (
+    fileDate: string,
+    filePath: Config.Path,
+    configStr: string,
+    options: CacheKeyOptions,
+  ) => Promise<string>;
+
+  process: (
+    sourceText: string,
+    sourcePath: Config.Path,
+    config: Config.ProjectConfig,
+    options?: TransformOptions,
+  ) => TransformedSource;
+
+  processAsync?: (
+    sourceText: string,
+    sourcePath: Config.Path,
+    config: Config.ProjectConfig,
+    options?: TransformOptions,
+  ) => Promise<TransformedSource>;
+}
+
+export type Transformer = SyncTransFormer | AsyncTransformer;