packager: attachHMRServer.js: Flow

Summary:
The breakage fixed by changeset [1] could have been identified earlier if we had typing on `attachHMRServer`, so I spent some time on that. This has revealed in turn a few functions across the codebase that were incorrectly typed, and that are now fixed.

[1] packager: attachHMRServer.js: fix callsite of Server#getModuleForPath()

Reviewed By: davidaurelio

Differential Revision: D4706241

fbshipit-source-id: fc4285245921ae45d5781a47d626fc0559dba998

packages/metro-bundler/src/Bundler/index.js

@@ -277,7 +277,7 @@ class Bundler {
     );
   }
 
-  hmrBundle(options: {platform: ?string}, host: string, port: number) {
+  hmrBundle(options: {platform: ?string}, host: string, port: number): Promise<HMRBundle> {
     return this._bundle({
       ...options,
       bundle: new HMRBundle({
@@ -492,7 +492,7 @@ class Bundler {
     minify?: boolean,
     hot?: boolean,
     generateSourceMaps?: boolean,
-  }) {
+  }): Promise<Array<Module>> {
     return this.getTransformOptions(
       entryFile,
       {

packages/metro-bundler/src/Resolver/index.js

@@ -87,7 +87,7 @@ class Resolver {
   getShallowDependencies(
     entryFile: string,
     transformOptions: TransformOptions,
-  ): Array<string> {
+  ): Promise<Array<Module>> {
     return this._depGraph.getShallowDependencies(entryFile, transformOptions);
   }
 

packages/metro-bundler/src/Server/index.js

@@ -31,6 +31,7 @@ import type {Stats} from 'fs';
 import type {IncomingMessage, ServerResponse} from 'http';
 import type ResolutionResponse from '../node-haste/DependencyGraph/ResolutionResponse';
 import type Bundle from '../Bundler/Bundle';
+import type HMRBundle from '../Bundler/HMRBundle';
 import type {Reporter} from '../lib/reporting';
 import type {GetTransformOptions} from '../Bundler';
 import type GlobalTransformCache from '../lib/GlobalTransformCache';
@@ -157,7 +158,7 @@ class Server {
   _assetServer: AssetServer;
   _bundler: Bundler;
   _debouncedFileChangeHandler: (filePath: string) => mixed;
-  _hmrFileChangeListener: (type: string, filePath: string) => mixed;
+  _hmrFileChangeListener: ?(type: string, filePath: string) => mixed;
   _reporter: Reporter;
   _symbolicateInWorker: Symbolicate;
 
@@ -244,9 +245,7 @@ class Server {
     return this._bundler.end();
   }
 
-  setHMRFileChangeListener(
-    listener: (type: string, filePath: string) => mixed,
-  ) {
+  setHMRFileChangeListener(listener: ?(type: string, filePath: string) => mixed) {
     this._hmrFileChangeListener = listener;
   }
 
@@ -276,7 +275,7 @@ class Server {
     return bundle;
   }
 
-  buildBundleFromUrl(reqUrl: string): Promise<mixed> {
+  buildBundleFromUrl(reqUrl: string): Promise<Bundle> {
     const options = this._getOptionsFromUrl(reqUrl);
     return this.buildBundle(options);
   }
@@ -285,14 +284,14 @@ class Server {
     options: {platform: ?string},
     host: string,
     port: number,
-  ): Promise<string> {
+  ): Promise<HMRBundle> {
     return this._bundler.hmrBundle(options, host, port);
   }
 
   getShallowDependencies(options: {
     entryFile: string,
     platform?: string,
-  }): Promise<mixed> {
+  }): Promise<Array<Module>> {
     return Promise.resolve().then(() => {
       if (!options.platform) {
         options.platform = getPlatformExtension(options.entryFile);
@@ -335,10 +334,11 @@ class Server {
     // If Hot Loading is enabled avoid rebuilding bundles and sending live
     // updates. Instead, send the HMR updates right away and clear the bundles
     // cache so that if the user reloads we send them a fresh bundle
-    if (this._hmrFileChangeListener) {
+    const {_hmrFileChangeListener} = this;
+    if (_hmrFileChangeListener) {
       // Clear cached bundles in case user reloads
       this._clearBundles();
-      this._hmrFileChangeListener(type, filePath);
+      _hmrFileChangeListener(type, filePath);
       return;
     } else if (type !== 'change' && filePath.indexOf(NODE_MODULES) !== -1) {
       // node module resolution can be affected by added or removed files

packages/metro-bundler/src/node-haste/index.js

@@ -173,7 +173,10 @@ class DependencyGraph extends EventEmitter {
    * Returns a promise with the direct dependencies the module associated to
    * the given entryPath has.
    */
-  getShallowDependencies(entryPath: string, transformOptions: TransformOptions) {
+  getShallowDependencies(
+    entryPath: string,
+    transformOptions: TransformOptions,
+  ): Promise<Array<Module>> {
     return this._moduleCache
       .getModule(entryPath)
       .getDependencies(transformOptions);