Make transformer result flow types generic all over the place

Reviewed By: jeanlauliac

Differential Revision: D7895095

fbshipit-source-id: df47f4b3e7a08e194fa1a2f874be87ead64ac198

packages/metro-cache/src/stores/FileStore.js

@@ -15,13 +15,11 @@ const mkdirp = require('mkdirp');
 const path = require('path');
 const rimraf = require('rimraf');
 
-import type {TransformedCode} from 'metro/src/JSTransformer/worker';
-
 export type Options = {|
   root: string,
 |};
 
-class FileStore {
+class FileStore<T> {
   _root: string;
 
   constructor(options: Options) {
@@ -29,7 +27,7 @@ class FileStore {
     this._createDirs();
   }
 
-  get(key: Buffer): ?TransformedCode {
+  get(key: Buffer): ?T {
     try {
       return JSON.parse(fs.readFileSync(this._getFilePath(key), 'utf8'));
     } catch (err) {
@@ -41,7 +39,7 @@ class FileStore {
     }
   }
 
-  set(key: Buffer, value: TransformedCode): void {
+  set(key: Buffer, value: T): void {
     fs.writeFileSync(this._getFilePath(key), JSON.stringify(value));
   }
 

packages/metro-cache/src/stores/HttpStore.js

@@ -15,8 +15,6 @@ const https = require('https');
 const url = require('url');
 const zlib = require('zlib');
 
-import type {TransformedCode} from 'metro/src/JSTransformer/worker';
-
 export type Options = {|
   endpoint: string,
   timeout?: number,
@@ -26,7 +24,7 @@ const ZLIB_OPTIONS = {
   level: 9,
 };
 
-class HttpStore {
+class HttpStore<T> {
   _module: typeof http | typeof https;
   _timeout: number;
 
@@ -63,7 +61,7 @@ class HttpStore {
     this._setAgent = new module.Agent(agentConfig);
   }
 
-  get(key: Buffer): Promise<?TransformedCode> {
+  get(key: Buffer): Promise<?T> {
     return new Promise((resolve, reject) => {
       const options = {
         agent: this._getAgent,
@@ -119,7 +117,7 @@ class HttpStore {
     });
   }
 
-  set(key: Buffer, value: TransformedCode): Promise<void> {
+  set(key: Buffer, value: T): Promise<void> {
     return new Promise((resolve, reject) => {
       const gzip = zlib.createGzip(ZLIB_OPTIONS);
 

packages/metro/src/Bundler.js

@@ -22,11 +22,7 @@ const toLocalPath = require('./node-haste/lib/toLocalPath');
 const {Cache, stableHash} = require('metro-cache');
 
 import type {TransformResult} from './DeltaBundler';
-import type {
+import type {WorkerOptions} from './JSTransformer/worker';
-  JsOutput,
-  WorkerOptions,
-  TransformedCode,
-} from './JSTransformer/worker';
 import type {DynamicRequiresBehavior} from './ModuleGraph/worker/collectDependencies';
 import type {Reporter} from './lib/reporting';
 import type {BabelSourceMap} from '@babel/core';
@@ -72,7 +68,7 @@ export type Options = {|
   +assetRegistryPath: string,
   +asyncRequireModulePath: string,
   +blacklistRE?: RegExp,
-  +cacheStores: $ReadOnlyArray<CacheStore<TransformedCode>>,
+  +cacheStores: $ReadOnlyArray<CacheStore<TransformResult<>>>,
   +cacheVersion: string,
   +dynamicDepsInPackages: DynamicRequiresBehavior,
   +enableBabelRCLookup: boolean,
@@ -100,7 +96,7 @@ const {hasOwnProperty} = Object.prototype;
 
 class Bundler {
   _opts: Options;
-  _cache: Cache<TransformedCode>;
+  _cache: Cache<TransformResult<>>;
   _baseHash: string;
   _transformer: Transformer;
   _depGraphPromise: Promise<DependencyGraph>;
@@ -218,7 +214,7 @@ class Bundler {
   async transformFile(
     filePath: string,
     transformCodeOptions: WorkerOptions,
-  ): Promise<TransformResult<JsOutput>> {
+  ): Promise<TransformResult<>> {
     const cache = this._cache;
 
     const {

packages/metro/src/Config.js

@@ -21,7 +21,7 @@ import type {
   PostMinifyProcess,
   PostProcessBundleSourcemap,
 } from './Bundler';
-import type {TransformedCode} from './JSTransformer/worker';
+import type {TransformResult} from './DeltaBundler';
 import type {DynamicRequiresBehavior} from './ModuleGraph/worker/collectDependencies';
 import type {IncomingMessage, ServerResponse} from 'http';
 import type {CacheStore} from 'metro-cache';
@@ -38,7 +38,7 @@ export type ConfigT = {
   /**
    * List of all store caches.
    */
-  cacheStores: Array<CacheStore<TransformedCode>>,
+  cacheStores: Array<CacheStore<TransformResult<>>>,
 
   /**
    * Can be used to generate a key that will invalidate the whole metro cache

packages/metro/src/DeltaBundler.js

@@ -13,7 +13,13 @@
 const DeltaCalculator = require('./DeltaBundler/DeltaCalculator');
 
 import type Bundler from './Bundler';
-import type {DeltaResult, Graph, Options} from './DeltaBundler/types.flow';
+import type {
+  DeltaResult,
+  Graph,
+  // eslint-disable-next-line no-unused-vars
+  MixedOutput,
+  Options,
+} from './DeltaBundler/types.flow';
 
 export type {
   DeltaResult,
@@ -29,7 +35,7 @@ export type {
  * concurrent clients requesting their own deltas. This is done through the
  * `clientId` param (which maps a client to a specific delta transformer).
  */
-class DeltaBundler<T> {
+class DeltaBundler<T = MixedOutput> {
   _bundler: Bundler;
   _deltaCalculators: Map<Graph<T>, DeltaCalculator<T>> = new Map();
 

packages/metro/src/DeltaBundler/Serializers/deltaJSBundle.js

@@ -15,7 +15,6 @@ const getAppendScripts = require('../../lib/getAppendScripts');
 const {wrapModule} = require('./helpers/js');
 const {getJsOutput, isJsModule} = require('./helpers/js');
 
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {DeltaResult, Graph, Module} from '../types.flow';
 
 type Options = {|
@@ -29,10 +28,10 @@ type Options = {|
 
 function deltaJSBundle(
   entryPoint: string,
-  pre: $ReadOnlyArray<Module<JsOutput>>,
+  pre: $ReadOnlyArray<Module<>>,
-  delta: DeltaResult<JsOutput>,
+  delta: DeltaResult<>,
   sequenceId: string,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): string {
   const outputPre = [];

packages/metro/src/DeltaBundler/Serializers/getAllFiles.js

@@ -13,7 +13,6 @@
 const {getAssetFiles} = require('../../Assets');
 const {getJsOutput, isJsModule} = require('./helpers/js');
 
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {Graph, Module} from '../types.flow';
 
 type Options = {|
@@ -21,8 +20,8 @@ type Options = {|
 |};
 
 async function getAllFiles(
-  pre: $ReadOnlyArray<Module<JsOutput>>,
+  pre: $ReadOnlyArray<Module<>>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): Promise<$ReadOnlyArray<string>> {
   const modules = graph.dependencies;

packages/metro/src/DeltaBundler/Serializers/getAssets.js

@@ -16,7 +16,6 @@ const {getAssetData} = require('../../Assets');
 const {getJsOutput, isJsModule} = require('./helpers/js');
 
 import type {AssetData} from '../../Assets';
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {Graph} from '../types.flow';
 
 type Options = {|
@@ -26,7 +25,7 @@ type Options = {|
 |};
 
 async function getAssets(
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): Promise<$ReadOnlyArray<AssetData>> {
   const promises = [];

packages/metro/src/DeltaBundler/Serializers/getRamBundleInfo.js

@@ -20,7 +20,6 @@ const {createRamBundleGroups} = require('../../Bundler/util');
 const {isJsModule, wrapModule} = require('./helpers/js');
 
 import type {GetTransformOptions} from '../../Bundler';
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {ModuleTransportLike} from '../../shared/types.flow';
 import type {Graph, Module} from '../types.flow';
 
@@ -45,8 +44,8 @@ export type RamBundleInfo = {|
 
 async function getRamBundleInfo(
   entryPoint: string,
-  pre: $ReadOnlyArray<Module<JsOutput>>,
+  pre: $ReadOnlyArray<Module<>>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): Promise<RamBundleInfo> {
   const modules = [

packages/metro/src/DeltaBundler/Serializers/helpers/js.js

@@ -15,7 +15,7 @@ const invariant = require('fbjs/lib/invariant');
 const path = require('path');
 
 import type {JsOutput} from '../../../JSTransformer/worker';
-import type {Module} from '../../types.flow';
+import type {MixedOutput, Module} from '../../types.flow';
 
 export type Options = {
   +createModuleId: string => number | string,
@@ -27,8 +27,9 @@ export type Options = {
 // Make sure to set PRINT_REQUIRE_PATHS = true too, and restart Metro
 const PASS_MODULE_PATHS_TO_DEFINE = false;
 
-function wrapModule(module: Module<JsOutput>, options: Options) {
+function wrapModule(module: Module<>, options: Options) {
   const output = getJsOutput(module);
+
   if (output.type.startsWith('js/script')) {
     return output.data.code;
   }
@@ -55,7 +56,7 @@ function wrapModule(module: Module<JsOutput>, options: Options) {
   return addParamsToDefineCall(output.data.code, ...params);
 }
 
-function getJsOutput(module: Module<JsOutput>) {
+function getJsOutput(module: Module<>): JsOutput {
   const jsModules = module.output.filter(({type}) => type.startsWith('js/'));
 
   invariant(
@@ -65,13 +66,15 @@ function getJsOutput(module: Module<JsOutput>) {
     } JS outputs.`,
   );
 
-  return jsModules[0];
+  return (jsModules[0]: any);
 }
 
-function isJsModule(module: Module<JsOutput>) {
+function isJsModule(module: Module<>): boolean {
-  const jsModules = module.output.filter(({type}) => type.startsWith('js/'));
+  return module.output.filter(isJsOutput).length > 0;
+}
 
-  return jsModules.length > 0;
+function isJsOutput(output: MixedOutput): boolean %checks {
+  return output.type.startsWith('js/');
 }
 
 module.exports = {

packages/metro/src/DeltaBundler/Serializers/hmrJSBundle.js

@@ -14,7 +14,6 @@ const addParamsToDefineCall = require('../../lib/addParamsToDefineCall');
 
 const {isJsModule, wrapModule} = require('./helpers/js');
 
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {DeltaResult, Graph, Module} from '../types.flow';
 
 type Options = {
@@ -31,8 +30,8 @@ export type Result = {
 };
 
 function hmrJSBundle(
-  delta: DeltaResult<JsOutput>,
+  delta: DeltaResult<>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): Result {
   const modules = [];
@@ -54,8 +53,8 @@ function hmrJSBundle(
 }
 
 function _prepareModule(
-  module: Module<JsOutput>,
+  module: Module<>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): {|+id: number, +code: string|} {
   const code = wrapModule(module, {
@@ -87,7 +86,7 @@ function _prepareModule(
  */
 function _getInverseDependencies(
   path: string,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   inverseDependencies: {[key: string]: Array<string>} = {},
 ): {[key: string]: Array<string>} {
   // Dependency alredy traversed.

packages/metro/src/DeltaBundler/Serializers/plainJSBundle.js

@@ -14,7 +14,6 @@ const getAppendScripts = require('../../lib/getAppendScripts');
 
 const {isJsModule, wrapModule} = require('./helpers/js');
 
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {Graph, Module} from '../types.flow';
 
 type Options = {|
@@ -28,8 +27,8 @@ type Options = {|
 
 function plainJSBundle(
   entryPoint: string,
-  pre: $ReadOnlyArray<Module<JsOutput>>,
+  pre: $ReadOnlyArray<Module<>>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options,
 ): string {
   for (const module of graph.dependencies.values()) {

packages/metro/src/DeltaBundler/Serializers/sourceMapObject.js

@@ -13,13 +13,12 @@
 const {isJsModule, getJsOutput} = require('./helpers/js');
 const {fromRawMappings} = require('metro-source-map');
 
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {Graph, Module} from '../types.flow';
 import type {BabelSourceMap} from '@babel/core';
 
 function fullSourceMapObject(
-  pre: $ReadOnlyArray<Module<JsOutput>>,
+  pre: $ReadOnlyArray<Module<>>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: {|+excludeSource: boolean|},
 ): BabelSourceMap {
   const modules = [...pre, ...graph.dependencies.values()]

packages/metro/src/DeltaBundler/Serializers/sourceMapString.js

@@ -13,12 +13,11 @@
 const {isJsModule, getJsOutput} = require('./helpers/js');
 const {fromRawMappings} = require('metro-source-map');
 
-import type {JsOutput} from '../../JSTransformer/worker';
 import type {Graph, Module} from '../types.flow';
 
 function fullSourceMap(
-  pre: $ReadOnlyArray<Module<JsOutput>>,
+  pre: $ReadOnlyArray<Module<>>,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: {|+excludeSource: boolean|},
 ): string {
   const modules = [...pre, ...graph.dependencies.values()]

packages/metro/src/DeltaBundler/types.flow.js

@@ -12,12 +12,17 @@
 
 import type {TransformResultDependency} from '../ModuleGraph/types.flow';
 
+export type MixedOutput = {|
+  +data: mixed,
+  +type: string,
+|};
+
 export type Dependency = {|
   +absolutePath: string,
   +data: TransformResultDependency,
 |};
 
-export type Module<T> = {|
+export type Module<T = MixedOutput> = {|
   dependencies: Map<string, Dependency>,
   inverseDependencies: Set<string>,
   output: $ReadOnlyArray<T>,
@@ -25,26 +30,28 @@ export type Module<T> = {|
   getSource: () => string,
 |};
 
-export type Graph<T> = {|
+export type Graph<T = MixedOutput> = {|
   dependencies: Map<string, Module<T>>,
   entryPoints: $ReadOnlyArray<string>,
 |};
 
-export type TransformResult<T> = {|
+export type TransformResult<T = MixedOutput> = {|
   dependencies: $ReadOnlyArray<TransformResultDependency>,
   output: $ReadOnlyArray<T>,
   +getSource: () => string,
 |};
 
-export type TransformFn<T> = string => Promise<TransformResult<T>>;
+export type TransformFn<T = MixedOutput> = string => Promise<
+  TransformResult<T>,
+>;
 
-export type Options<T> = {|
+export type Options<T = MixedOutput> = {|
   resolve: (from: string, to: string) => string,
   transform: TransformFn<T>,
   onProgress: ?(numProcessed: number, total: number) => mixed,
 |};
 
-export type DeltaResult<T> = {|
+export type DeltaResult<T = MixedOutput> = {|
   +modified: Map<string, Module<T>>,
   +deleted: Set<string>,
   +reset: boolean,

packages/metro/src/HmrServer.js

@@ -21,11 +21,11 @@ const {
   Logger: {createActionStartEntry, createActionEndEntry, log},
 } = require('metro-core');
 
-import type PackagerServer, {JsGraph} from './Server';
+import type PackagerServer, {OutputGraph} from './Server';
 import type {Reporter} from './lib/reporting';
 
 type Client = {|
-  graph: JsGraph,
+  graph: OutputGraph,
   sendFn: (data: string) => mixed,
 |};
 

packages/metro/src/JSTransformer.js

@@ -16,7 +16,8 @@ const {Logger} = require('metro-core');
 const debug = require('debug')('Metro:JStransformer');
 const Worker = require('jest-worker').default;
 
-import type {TransformedCode, WorkerOptions} from './JSTransformer/worker';
+import type {TransformResult} from './DeltaBundler';
+import type {WorkerOptions} from './JSTransformer/worker';
 import type {LocalPath} from './node-haste/lib/toLocalPath';
 import type {DynamicRequiresBehavior} from './ModuleGraph/worker/collectDependencies';
 
@@ -32,7 +33,7 @@ type Reporters = {
 };
 
 type TransformerResult = {
-  result: TransformedCode,
+  result: TransformResult<>,
   sha1: string,
 };
 

packages/metro/src/JSTransformer/worker.js

@@ -84,26 +84,24 @@ export type WorkerOptions = {|
   +projectRoot: string,
 |};
 
-export type Data = {
+export type JsOutput = {|
-  result: TransformedCode,
+  +data: {|
+    +code: string,
+    +map: Array<MetroSourceMapSegmentTuple>,
+  |},
+  +type: string,
+|};
+
+type Data = {
+  result: {|
+    output: $ReadOnlyArray<JsOutput>,
+    dependencies: $ReadOnlyArray<TransformResultDependency>,
+  |},
   sha1: string,
   transformFileStartLogEntry: LogEntry,
   transformFileEndLogEntry: LogEntry,
 };
 
-export type JsOutput = {|
-  data: {
-    +code: string,
-    +map: Array<MetroSourceMapSegmentTuple>,
-  },
-  type: string,
-|};
-
-export type TransformedCode = {|
-  output: $ReadOnlyArray<JsOutput>,
-  dependencies: $ReadOnlyArray<TransformResultDependency>,
-|};
-
 function getDynamicDepsBehavior(
   inPackages: DynamicRequiresBehavior,
   filename: string,

packages/metro/src/Server.js

@@ -42,7 +42,7 @@ const {getAsset} = require('./Assets');
 const resolveSync: ResolveSync = require('resolve').sync;
 
 import type {CustomError} from './lib/formatBundlingError';
-import type {DeltaResult, Graph, Module} from './DeltaBundler';
+import type {DeltaResult, Graph, Module, TransformResult} from './DeltaBundler';
 import type {IncomingMessage, ServerResponse} from 'http';
 import type {Reporter} from './lib/reporting';
 import type {RamBundleInfo} from './DeltaBundler/Serializers/getRamBundleInfo';
@@ -57,11 +57,7 @@ import type {CustomResolver} from 'metro-resolver';
 import type {MetroSourceMap} from 'metro-source-map';
 import type {Symbolicate} from './Server/symbolicate/symbolicate';
 import type {AssetData} from './Assets';
-import type {
+import type {CustomTransformOptions} from './JSTransformer/worker';
-  CustomTransformOptions,
-  JsOutput,
-  TransformedCode,
-} from './JSTransformer/worker';
 
 const {
   Logger: {createActionStartEntry, createActionEndEntry, log},
@@ -70,8 +66,8 @@ const {
 type ResolveSync = (path: string, opts: ?{baseDir?: string}) => string;
 
 type GraphInfo = {|
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
-  prepend: $ReadOnlyArray<Module<JsOutput>>,
+  prepend: $ReadOnlyArray<Module<>>,
   lastModified: Date,
   +sequenceId: string,
 |};
@@ -87,7 +83,7 @@ export type BuildGraphOptions = {|
   +type: 'module' | 'script',
 |};
 
-export type JsGraph = Graph<JsOutput>;
+export type OutputGraph = Graph<>;
 
 type DeltaOptions = BundleOptions & {
   deltaBundleId: ?string,
@@ -108,7 +104,7 @@ class Server {
   _opts: {
     assetExts: Array<string>,
     blacklistRE: void | RegExp,
-    cacheStores: $ReadOnlyArray<CacheStore<TransformedCode>>,
+    cacheStores: $ReadOnlyArray<CacheStore<TransformResult<>>>,
     cacheVersion: string,
     createModuleId: (path: string) => number,
     enableBabelRCLookup: boolean,
@@ -145,7 +141,7 @@ class Server {
   _symbolicateInWorker: Symbolicate;
   _platforms: Set<string>;
   _nextBundleBuildID: number;
-  _deltaBundler: DeltaBundler<JsOutput>;
+  _deltaBundler: DeltaBundler<>;
   _graphs: Map<string, Promise<GraphInfo>> = new Map();
   _deltaGraphs: Map<string, Promise<GraphInfo>> = new Map();
 
@@ -258,7 +254,7 @@ class Server {
     this._bundler.end();
   }
 
-  getDeltaBundler(): DeltaBundler<JsOutput> {
+  getDeltaBundler(): DeltaBundler<> {
     return this._deltaBundler;
   }
 
@@ -288,7 +284,7 @@ class Server {
   async buildGraph(
     entryFiles: $ReadOnlyArray<string>,
     options: BuildGraphOptions,
-  ): Promise<JsGraph> {
+  ): Promise<OutputGraph> {
     entryFiles = entryFiles.map(entryFile =>
       getAbsolutePath(entryFile, this._opts.projectRoots),
     );
@@ -447,7 +443,7 @@ class Server {
 
   async _getDeltaInfo(
     options: DeltaOptions,
-  ): Promise<{...GraphInfo, delta: DeltaResult<JsOutput>}> {
+  ): Promise<{...GraphInfo, delta: DeltaResult<>}> {
     const id = this._optionsHash(options);
     let graphPromise = this._deltaGraphs.get(id);
     let graphInfo;

packages/metro/src/index.js

@@ -31,7 +31,7 @@ const {readFile} = require('fs-extra');
 const {Terminal} = require('metro-core');
 
 import type {ConfigT} from './Config';
-import type {JsGraph} from './Server';
+import type {Graph} from './DeltaBundler';
 import type {Reporter} from './lib/reporting';
 import type {RequestOptions, OutputOptions} from './shared/types.flow.js';
 import type {Options as ServerOptions} from './shared/types.flow';
@@ -381,7 +381,7 @@ exports.buildGraph = async function({
   platform = `web`,
   type = 'module',
   ...rest
-}: BuildGraphOptions): Promise<JsGraph> {
+}: BuildGraphOptions): Promise<Graph<>> {
   const metroServer = await runMetro({
     ...rest,
     config,

packages/metro/src/lib/getAppendScripts.js

@@ -11,7 +11,6 @@
 'use strict';
 
 import type {Graph, Module} from '../DeltaBundler';
-import type {JsOutput} from '../JSTransformer/worker';
 
 type Options<T: number | string> = {
   +createModuleId: string => T,
@@ -23,9 +22,9 @@ type Options<T: number | string> = {
 
 function getAppendScripts<T: number | string>(
   entryPoint: string,
-  graph: Graph<JsOutput>,
+  graph: Graph<>,
   options: Options<T>,
-): $ReadOnlyArray<Module<JsOutput>> {
+): $ReadOnlyArray<Module<>> {
   const output = [];
 
   if (options.runModule) {

packages/metro/src/lib/getPrependedScripts.js

@@ -16,7 +16,7 @@ const transformHelpers = require('./transformHelpers');
 
 import type Bundler from '../Bundler';
 import type DeltaBundler, {Module} from '../DeltaBundler';
-import type {CustomTransformOptions, JsOutput} from '../JSTransformer/worker';
+import type {CustomTransformOptions} from '../JSTransformer/worker';
 
 type Options = {
   getPolyfills: ({platform: ?string}) => $ReadOnlyArray<string>,
@@ -35,8 +35,8 @@ async function getPrependedScripts(
   options: Options,
   bundleOptions: BundleOptions,
   bundler: Bundler,
-  deltaBundler: DeltaBundler<JsOutput>,
+  deltaBundler: DeltaBundler<>,
-): Promise<Array<Module<JsOutput>>> {
+): Promise<$ReadOnlyArray<Module<>>> {
   // Get all the polyfills from the relevant option params (the
   // `getPolyfills()` method and the `polyfillModuleNames` variable).
   const polyfillModuleNames = options
@@ -79,7 +79,7 @@ async function getPrependedScripts(
   ];
 }
 
-function _getPrelude({dev}: {dev: boolean}): Module<JsOutput> {
+function _getPrelude({dev}: {dev: boolean}): Module<> {
   const code = getPreludeCode({isDev: dev});
   const name = '__prelude__';
 

packages/metro/src/lib/transformHelpers.js

@@ -12,7 +12,7 @@
 
 import type Bundler from '../Bundler';
 import type DeltaBundler, {TransformFn} from '../DeltaBundler';
-import type {JsOutput, WorkerOptions} from '../JSTransformer/worker';
+import type {WorkerOptions} from '../JSTransformer/worker';
 import type {BuildGraphOptions} from '../Server';
 
 type InlineRequiresRaw = {+blacklist: {[string]: true}} | boolean;
@@ -20,7 +20,7 @@ type InlineRequiresRaw = {+blacklist: {[string]: true}} | boolean;
 async function calcTransformerOptions(
   entryFiles: $ReadOnlyArray<string>,
   bundler: Bundler,
-  deltaBundler: DeltaBundler<JsOutput>,
+  deltaBundler: DeltaBundler<>,
   options: BuildGraphOptions,
 ): Promise<{...WorkerOptions, inlineRequires: InlineRequiresRaw}> {
   const {
@@ -85,9 +85,9 @@ function removeInlineRequiresBlacklistFromOptions(
 async function getTransformFn(
   entryFiles: $ReadOnlyArray<string>,
   bundler: Bundler,
-  deltaBundler: DeltaBundler<JsOutput>,
+  deltaBundler: DeltaBundler<>,
   options: BuildGraphOptions,
-): Promise<TransformFn<JsOutput>> {
+): Promise<TransformFn<>> {
   const {inlineRequires, ...transformerOptions} = await calcTransformerOptions(
     entryFiles,
     bundler,

packages/metro/src/shared/types.flow.js

@@ -14,10 +14,8 @@ import type {
   PostMinifyProcess,
   PostProcessBundleSourcemap,
 } from '../Bundler';
-import type {
+import type {TransformResult} from '../DeltaBundler';
-  CustomTransformOptions,
+import type {CustomTransformOptions} from '../JSTransformer/worker';
-  TransformedCode,
-} from '../JSTransformer/worker';
 import type {DynamicRequiresBehavior} from '../ModuleGraph/worker/collectDependencies';
 import type {Reporter} from '../lib/reporting';
 import type {CacheStore} from 'metro-cache';
@@ -80,7 +78,7 @@ export type Options = {|
   +asyncRequireModulePath: string,
   +assetRegistryPath: string,
   blacklistRE?: RegExp,
-  cacheStores: $ReadOnlyArray<CacheStore<TransformedCode>>,
+  cacheStores: $ReadOnlyArray<CacheStore<TransformResult<>>>,
   cacheVersion: string,
   createModuleIdFactory?: () => (path: string) => number,
   +dynamicDepsInPackages: DynamicRequiresBehavior,