Support for remote assets

Reviewed By: davidaurelio

Differential Revision: D6030886

fbshipit-source-id: c188b39e104f5c3f65a98336fecbffc93091ff4c

flow-typed/babel.js.flow

@@ -89,9 +89,9 @@ type __TransformOptions = {
 
 type _TransformOptions =
   __TransformOptions & {env?: {[key: string]: __TransformOptions}};
-declare class _Ast {}
+declare class Ast {}
 type TransformResult = {
-  ast: _Ast,
+  ast: Ast,
   code: ?string,
   ignored: boolean,
   map: ?_SourceMap,
@@ -101,14 +101,14 @@ type VisitFn = <State>(path: Object, state: State) => any;
 declare module 'babel-core' {
   declare type Plugins = _Plugins;
   declare type SourceMap = _SourceMap;
-  declare type Ast = _Ast;
+  declare type Ast = Ast;
   declare type TransformOptions = _TransformOptions;
   declare function transform(
     code: string,
     options?: _TransformOptions,
   ): TransformResult;
   declare function traverse<State>(
-    ast: _Ast,
+    ast: Ast,
     visitor: {[key: string]: VisitFn<State> |
                              {enter?: VisitFn<State>, exit?: VisitFn<State>}},
     scope?: ?Object,
@@ -117,7 +117,7 @@ declare module 'babel-core' {
   ): void;
   declare var types: {[key: string]: Function};
   declare function transformFromAst(
-    ast: _Ast,
+    ast: Ast,
     code?: ?string,
     babelOptions?: _TransformOptions,
   ): TransformResult;
@@ -133,7 +133,7 @@ type RawMapping = {
 declare module 'babel-generator' {
   declare type RawMapping = RawMapping;
   declare function exports(
-    ast: _Ast,
+    ast: Ast,
     options?: GeneratorOptions,
   ): TransformResult & {rawMappings: ?Array<RawMapping>};
 }

packages/metro-bundler/src/Bundler/__tests__/util-test.js

@@ -0,0 +1,52 @@
+/**
+ * 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.
+ *
+ * @emails oncall+javascript_foundation
+ * @format
+ */
+
+'use strict';
+
+const generator = require('babel-generator').default;
+const util = require('../util');
+
+it('generates the right AST for remote assets', () => {
+  const asset = {
+    __packager_asset: true,
+    fileSystemLocation: '/js/RKJSModules/Apps/Wilde/AdsPayments/images',
+    hash: '3e9b7b3c4d4fa37f9eb580dc426412dbde2925ff',
+    height: 48,
+    httpServerLocation: '/assets/RKJSModules/Apps/Wilde/AdsPayments/images',
+    name: 'pending',
+    scales: [1.5, 2, 3, 4],
+    type: 'png',
+    width: 48,
+  };
+
+  const map = {
+    '/js/RKJSModules/Apps/Wilde/AdsPayments/images': {
+      pending: {
+        '2': 'img2x',
+        '3': 'img3x',
+      },
+    },
+  };
+
+  const {ast} = util.generateRemoteAssetCodeFileAst(
+    'gen',
+    asset,
+    'https://remote.server.com/',
+    map,
+  );
+
+  const code = generator(ast, {minified: true}).code;
+
+  expect(code).toBe(
+    'module.exports={"uri":"https://remote.server.com/"+{"2":"img2x","3":"img3x"}[require("gen").pickScale([2,3])]};',
+  );
+});

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

@@ -86,7 +86,6 @@ export type AssetDescriptor = {
 
 export type ExtendedAssetDescriptor = AssetDescriptor & {
   +fileSystemLocation: string,
-  +files: Array<string>,
 };
 
 const sizeOf = denodeify(imageSize);

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

@@ -16,7 +16,7 @@ const babel = require('babel-core');
 const babelGenerate = require('babel-generator').default;
 const babylon = require('babylon');
 
-import type {AssetDescriptor} from '.';
+import type {AssetDescriptor, ExtendedAssetDescriptor} from '.';
 import type {ModuleTransportLike} from '../shared/types.flow';
 
 type SubTree<T: ModuleTransportLike> = (
@@ -26,10 +26,104 @@ type SubTree<T: ModuleTransportLike> = (
 
 const assetPropertyBlacklist = new Set(['files', 'fileSystemLocation', 'path']);
 
+// Structure of the object: dir.name.scale = asset
+export type RemoteFileMap = {
+  [string]: {
+    [string]: {
+      [number]: string,
+    },
+  },
+};
+
+// Structure of the object: platform.dir.name.scale = asset
+export type PlatformRemoteFileMap = {
+  ['ios' | 'android']: RemoteFileMap,
+};
+
+type AssetResult = {
+  remote: boolean,
+  ast: Ast,
+};
+
+/**
+ * Generates the code involved in requiring an asset, but to be loaded remotely.
+ * If the asset cannot be found within the map, then it falls back to the
+ * standard asset.
+ */
+function generateRemoteAssetCodeFileAst(
+  assetSourceResolverPath: string,
+  assetDescriptor: ExtendedAssetDescriptor,
+  remoteServer: string,
+  remoteFileMap: RemoteFileMap,
+): ?AssetResult {
+  const t = babel.types;
+
+  const file = remoteFileMap[assetDescriptor.fileSystemLocation];
+  const descriptor = file && file[assetDescriptor.name];
+
+  if (!descriptor) {
+    return null;
+  }
+
+  // require('AssetSourceResolver')
+  const requireCall = t.callExpression(t.identifier('require'), [
+    t.stringLiteral(assetSourceResolverPath),
+  ]);
+
+  // require('AssetSourceResolver').pickScale
+  const pickScale = t.memberExpression(requireCall, t.identifier('pickScale'));
+
+  // require('AssetSourceResolver').pickScale([2, 3, ...])
+  const call = t.callExpression(pickScale, [
+    t.arrayExpression(
+      Object.keys(descriptor)
+        .map(Number)
+        .sort((a, b) => a - b)
+        .map(scale => t.numericLiteral(scale)),
+    ),
+  ]);
+
+  // {2: 'path/to/image@2x', 3: 'path/to/image@3x', ...}
+  const data = babylon.parseExpression(JSON.stringify(descriptor));
+
+  // ({2: '...', 3: '...'})[require(...).pickScale(...)]
+  const handler = t.memberExpression(data, call, true);
+
+  // 'https://remote.server.com/' + ({2: ...})[require(...).pickScale(...)]
+  const result = t.binaryExpression(
+    '+',
+    t.stringLiteral(remoteServer),
+    handler,
+  );
+
+  // module.exports
+  const moduleExports = t.memberExpression(
+    t.identifier('module'),
+    t.identifier('exports'),
+  );
+
+  return {
+    remote: true,
+    ast: t.file(
+      t.program([
+        t.expressionStatement(
+          t.assignmentExpression(
+            '=',
+            moduleExports,
+            t.objectExpression([
+              t.objectProperty(t.stringLiteral('uri'), result),
+            ]),
+          ),
+        ),
+      ]),
+    ),
+  };
+}
+
 function generateAssetCodeFileAst(
   assetRegistryPath: string,
   assetDescriptor: AssetDescriptor,
-): Object {
+): AssetResult {
   const properDescriptor = filterObject(
     assetDescriptor,
     assetPropertyBlacklist,
@@ -52,13 +146,16 @@ function generateAssetCodeFileAst(
   const registerAssetCall = t.callExpression(registerAssetFunction, [
     descriptorAst,
   ]);
-  return t.file(
-    t.program([
-      t.expressionStatement(
-        t.assignmentExpression('=', moduleExports, registerAssetCall),
-      ),
-    ]),
-  );
+  return {
+    remote: false,
+    ast: t.file(
+      t.program([
+        t.expressionStatement(
+          t.assignmentExpression('=', moduleExports, registerAssetCall),
+        ),
+      ]),
+    ),
+  };
 }
 
 function generateAssetTransformResult(
@@ -70,7 +167,7 @@ function generateAssetTransformResult(
   dependencyOffsets: Array<number>,
 |} {
   const {code} = babelGenerate(
-    generateAssetCodeFileAst(assetRegistryPath, assetDescriptor),
+    generateAssetCodeFileAst(assetRegistryPath, assetDescriptor).ast,
     {comments: false, compact: true},
   );
   const dependencies = [assetRegistryPath];
@@ -177,5 +274,6 @@ module.exports = {
   createRamBundleGroups,
   generateAssetCodeFileAst,
   generateAssetTransformResult,
+  generateRemoteAssetCodeFileAst,
   isAssetTypeAnImage,
 };

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

@@ -157,6 +157,7 @@ export type TransformedCodeFile = {
   +hasteID: ?string,
   package?: PackageData,
   +transformed: TransformResults,
+  +remoteAsset?: boolean,
   +type: CodeFileTypes,
 };