packager: add preprocess for buck worker

Summary: For the Buck integration (work-in-progress), we want to add the ability to do some custom preprocessing similar to the packager server. The signature is different so I prefer to have a separate function for that. Also we don't need the transform options right now, I suggest we don't add them for now and add them later if necessary.

Reviewed By: davidaurelio

Differential Revision: D5094632

fbshipit-source-id: 1775ddef90b331deabc5be3e57a67436bce06c82

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

@@ -22,6 +22,7 @@ import type {
   GraphFn,
   GraphResult,
   Module,
+  PostProcessModules,
 } from './types.flow';
 
 type BuildFn = (
@@ -37,6 +38,7 @@ type BuildOptions = {|
 
 exports.createBuildSetup = (
   graph: GraphFn,
+  postProcessModules: PostProcessModules,
   translateDefaultsPath: string => string = x => x,
 ): BuildFn =>
   (entryPoints, options, callback) => {
@@ -51,10 +53,16 @@ exports.createBuildSetup = (
     const graphOnlyModules = seq(graphWithOptions, getModules);
 
     parallel({
-      graph: cb => graphWithOptions(
+      graph: cb => graphWithOptions(entryPoints, (error, result) => {
-        entryPoints,
+        if (error) {
-        cb,
+          cb(error);
-      ),
+          return;
+        }
+        /* $FlowFixMe: not undefined if there is no error */
+        const {modules, entryModules} = result;
+        const prModules = postProcessModules(modules, [...entryPoints]);
+        cb(null, {modules: prModules, entryModules});
+      }),
       moduleSystem: cb => graphOnlyModules(
         [translateDefaultsPath(defaults.moduleSystem)],
         cb,

packages/metro-bundler/src/ModuleGraph/__tests__/ModuleGraph-test.js

@@ -16,7 +16,9 @@ const defaults = require('../../../defaults');
 const FILE_TYPE = 'module';
 
 describe('build setup', () => {
-  const buildSetup = ModuleGraph.createBuildSetup(graph);
+  const buildSetup = ModuleGraph.createBuildSetup(graph, mds => {
+    return [...mds].sort((l, r) => l.file.path > r.file.path);
+  });
   const noOptions = {};
   const noEntryPoints = [];
 
@@ -72,11 +74,11 @@ describe('build setup', () => {
     });
   });
 
-  it('places all entry points at the end', done => {
+  it('places all entry points and dependencies at the end, post-processed', done => {
-    const entryPoints = ['a', 'b', 'c'];
+    const entryPoints = ['b', 'c', 'd'];
     buildSetup(entryPoints, noOptions, (error, result) => {
-      expect(Array.from(result.modules).slice(-3))
+      expect(Array.from(result.modules).slice(-4))
-        .toEqual(entryPoints.map(moduleFromPath));
+        .toEqual(['a', 'b', 'c', 'd'].map(moduleFromPath));
       done();
     });
   });
@@ -84,7 +86,7 @@ describe('build setup', () => {
 
 function moduleFromPath(path) {
   return {
-    dependencies: [],
+    dependencies: path === 'b' ? ['a'] : [],
     file: {
       code: '',
       path,
@@ -95,8 +97,12 @@ function moduleFromPath(path) {
 
 function graph(entryPoints, platform, options, callback) {
   const modules = Array.from(entryPoints, moduleFromPath);
+  const depModules = Array.prototype.concat.apply(
+    [],
+    modules.map(x => x.dependencies.map(moduleFromPath)),
+  );
   callback(null, {
     entryModules: modules,
-    modules,
+    modules: modules.concat(depModules),
   });
 }

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

@@ -70,6 +70,11 @@ export type Module = {|
   file: File,
 |};
 
+export type PostProcessModules = (
+  modules: Iterable<Module>,
+  entryPoints: Array<string>,
+) => Iterable<Module>;
+
 export type OutputFn = ({|
   filename: string,
   idForPath: IdForPathFn,