RN buck: move asset work into transform worker

Reviewed By: davidaurelio

Differential Revision: D5872268

fbshipit-source-id: 829a0d26930f8893b93a5f42ef7026350dc01f29

packages/metro-bundler/src/ModuleGraph/types.flow.js

@@ -141,9 +141,46 @@ export type TransformedCodeFile = {
   +type: CodeFileTypes,
 };
 
+export type ImageSize = {|+width: number, +height: number|};
+
 export type AssetFile = {|
-  +assetContentBase64: string,
+  /**
+   * The path of the asset that is shared by all potential variants
+   * of this asset. For example `foo/bar@3x.png` would have the
+   * asset path `foo/bar.png`.
+   */
+  +assetPath: string,
+  /**
+   * The content is encoded in Base64 so that it can be stored in JSON files,
+   * that are used to communicate between different commands of a Buck
+   * build worker, for example.
+   */
+  +contentBase64: string,
+  /**
+   * Guessed from the file extension, for example `png` or `html`.
+   */
+  +contentType: string,
+  /**
+   * The path of the original file for this asset. For example
+   * `foo/bar@3x.ios.png`. This is most useful for reporting purposes, such as
+   * error messages.
+   */
   +filePath: string,
+  /**
+   * If the asset is an image, this contain the size in physical pixels (ie.
+   * regarless of whether it's a `@2x` or `@3x` version of a smaller image).
+   */
+  +physicalSize: ?ImageSize,
+  /**
+   * The platform this asset is designed for, for example `ios` if the file name
+   * is `foo.ios.js`. `null` if the asset is not platform-specific.
+   */
+  +platform: ?string,
+  /**
+   * The scale this asset is designed for, for example `2`
+   * if the file name is `foo@2x.png`.
+   */
+  +scale: number,
 |};
 
 export type TransformedSourceFile =

packages/metro-bundler/src/ModuleGraph/worker/Platforms.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) 2016-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';
+
+/**
+ * By knowing all the valid platforms, we're able to say that "foo.ios.png" is
+ * effectively the asset "foo" specific to "ios", and not a generic asset
+ * "foo.ios". This is important so that we can discard asset variants that don't
+ * match the platform being built.
+ */
+const VALID_PLATFORMS: Set<string> = new Set(['ios', 'android', 'web']);
+
+module.exports = {VALID_PLATFORMS};

packages/metro-bundler/src/ModuleGraph/worker/transform-module.js

@@ -12,19 +12,24 @@
 
 'use strict';
 
+const AssetPaths = require('../../node-haste/lib/AssetPaths');
 const JsFileWrapping = require('./JsFileWrapping');
+const Platforms = require('./Platforms');
 
 const collectDependencies = require('./collect-dependencies');
 const defaults = require('../../defaults');
 const docblock = require('jest-docblock');
 const generate = require('./generate');
+const getImageSize = require('image-size');
 const invariant = require('fbjs/lib/invariant');
 const path = require('path');
 
+const {isAssetTypeAnImage} = require('../../Bundler/util');
 const {basename} = require('path');
 
 import type {HasteImpl} from '../../node-haste/Module';
 import type {
+  ImageSize,
   TransformedCodeFile,
   TransformedSourceFile,
   Transformer,
@@ -147,13 +152,27 @@ function transformAsset<ExtraOptions: {}>(
   content: Buffer,
   options: TransformOptions<ExtraOptions>,
 ): TransformedSourceFile {
-  return {
-    details: {
-      assetContentBase64: content.toString('base64'),
-      filePath: options.filename,
-    },
-    type: 'asset',
+  const filePath = options.filename;
+  const assetData = AssetPaths.parse(filePath, Platforms.VALID_PLATFORMS);
+  const contentType = path.extname(filePath).slice(1);
+  const details = {
+    assetPath: assetData.assetName,
+    contentBase64: content.toString('base64'),
+    contentType,
+    filePath,
+    physicalSize: getAssetSize(contentType, content),
+    platform: assetData.platform,
+    scale: assetData.resolution,
   };
+  return {details, type: 'asset'};
+}
+
+function getAssetSize(type: string, content: Buffer): ?ImageSize {
+  if (!isAssetTypeAnImage(type)) {
+    return null;
+  }
+  const {width, height} = getImageSize(content);
+  return {width, height};
 }
 
 function makeResult(ast: Ast, filename, sourceCode, isPolyfill = false) {