metro-bundler: ResolutionRequest: extract FileNameResolver

Summary: I want to untangle `ResolutionRequest` once and for all, that starts by pulling stuff out :-)

Reviewed By: cpojer

Differential Revision: D5155316

fbshipit-source-id: a46ee9b40c6705edcac169adcfdffe25058ec810

packages/metro-bundler/src/node-haste/DependencyGraph/FileNameResolver.js

@@ -0,0 +1,46 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
+ * @format
+ */
+
+'use strict';
+
+const path = require('path');
+
+export type Options = {|
+  +dirPath: string,
+  +doesFileExist: (filePath: string) => boolean,
+|};
+
+/**
+ * When resolving a single module we want to keep track of the list of paths
+ * we tried to find. This class is a way to aggregate all the tries easily.
+ */
+class FileNameResolver {
+  _options: Options;
+  _tentativeFileNames: Array<string>;
+
+  constructor(options: Options) {
+    this._options = options;
+    this._tentativeFileNames = [];
+  }
+
+  getTentativeFileNames(): $ReadOnlyArray<string> {
+    return this._tentativeFileNames;
+  }
+
+  tryToResolveFileName(fileName: string): boolean {
+    this._tentativeFileNames.push(fileName);
+    const filePath = path.join(this._options.dirPath, fileName);
+    return this._options.doesFileExist(filePath);
+  }
+}
+
+module.exports = FileNameResolver;

packages/metro-bundler/src/node-haste/DependencyGraph/ResolutionRequest.js

@@ -13,6 +13,7 @@
 'use strict';
 
 const AsyncTaskGroup = require('../lib/AsyncTaskGroup');
+const FileNameResolver = require('./FileNameResolver');
 const MapWithDefaults = require('../lib/MapWithDefaults');
 
 const debug = require('debug')('RNP:DependencyGraph');
@@ -839,35 +840,6 @@ function resolutionHash(modulePath, depName) {
   return `${path.resolve(modulePath)}:${depName}`;
 }
 
-type FileNameResolverOptions = {|
-  +dirPath: string,
-  +doesFileExist: (filePath: string) => boolean,
-|};
-
-/**
- * When resolving a single module we want to keep track of the list of paths
- * we tried to find.
- */
-class FileNameResolver {
-  _options: FileNameResolverOptions;
-  _tentativeFileNames: Array<string>;
-
-  constructor(options: FileNameResolverOptions) {
-    this._options = options;
-    this._tentativeFileNames = [];
-  }
-
-  getTentativeFileNames(): $ReadOnlyArray<string> {
-    return this._tentativeFileNames;
-  }
-
-  tryToResolveFileName(fileName: string): boolean {
-    this._tentativeFileNames.push(fileName);
-    const filePath = path.join(this._options.dirPath, fileName);
-    return this._options.doesFileExist(filePath);
-  }
-}
-
 class UnableToResolveError extends Error {
   type: string;
   from: string;