Make reloads faster for simple file changes

Summary:
This is a very hacky solution to make reloads from packager faster for simple file changes.

Simple means that no dependencies have changed, otherwise packager will abort the attempt to update and fall back to the usual rebuilding method.

In principle, this change avoids re-walking and analyzing the whole dependency tree, and just updates modules in existing bundles.

Reviewed By: bestander

Differential Revision: D3713704

fbshipit-source-id: ba182325c4f4003c0a7402ea87444a94c75ebaf8

react-packager/src/Bundler/Bundle.js

@@ -59,7 +59,7 @@ class Bundle extends BundleBase {
       this._addRequireCall(super.getMainModuleId());
     }
 
-    super.finalize();
+    super.finalize(options);
   }
 
   _addRequireCall(moduleId) {

react-packager/src/Bundler/BundleBase.js

@@ -59,8 +59,10 @@ class BundleBase {
   }
 
   finalize(options) {
+    if (!options.allowUpdates) {
       Object.freeze(this._modules);
       Object.freeze(this._assets);
+    }
 
     this._finalized = true;
   }
@@ -76,6 +78,10 @@ class BundleBase {
     return this._source;
   }
 
+  invalidateSource() {
+    this._source = null;
+  }
+
   assertFinalized(message) {
     if (!this._finalized) {
       throw new Error(message || 'Bundle needs to be finalized before getting any source');

react-packager/src/Bundler/__tests__/Bundler-test.js

@@ -129,6 +129,7 @@ describe('Bundler', function() {
         dependencies: modules,
         transformOptions,
         getModuleId: () => 123,
+        getResolvedDependencyPairs: () => [],
       })
     );
 
@@ -141,7 +142,7 @@ describe('Bundler', function() {
     });
   });
 
-  pit('create a bundle', function() {
+  it('create a bundle', function() {
     assetServer.getAssetData.mockImpl(() => {
       return {
         scales: [1,2,3],
@@ -170,9 +171,11 @@ describe('Bundler', function() {
         expect(ithAddedModule(3)).toEqual('/root/img/new_image.png');
         expect(ithAddedModule(4)).toEqual('/root/file.json');
 
-        expect(bundle.finalize.mock.calls[0]).toEqual([
+        expect(bundle.finalize.mock.calls[0]).toEqual([{
-          {runMainModule: true, runBeforeMainModule: []}
+            runMainModule: true,
-        ]);
+            runBeforeMainModule: [],
+            allowUpdates: false,
+        }]);
 
         expect(bundle.addAsset.mock.calls[0]).toEqual([{
           __packager_asset: true,

react-packager/src/Bundler/index.js

@@ -89,6 +89,10 @@ const validateOpts = declareOpts({
     type: 'boolean',
     default: false,
   },
+  allowBundleUpdates: {
+    type: 'boolean',
+    default: false,
+  },
 });
 
 const assetPropertyBlacklist = new Set([
@@ -280,6 +284,7 @@ class Bundler {
         bundle.finalize({
           runMainModule,
           runBeforeMainModule: runBeforeMainModuleIds,
+          allowUpdates: this._opts.allowBundleUpdates,
         });
         return bundle;
       });
@@ -402,6 +407,7 @@ class Bundler {
           entryFilePath,
           transformOptions: response.transformOptions,
           getModuleId: response.getModuleId,
+          dependencyPairs: response.getResolvedDependencyPairs(module),
         }).then(transformed => {
           modulesByName[transformed.name] = module;
           onModuleTransformed({
@@ -533,7 +539,14 @@ class Bundler {
     );
   }
 
-  _toModuleTransport({module, bundle, entryFilePath, transformOptions, getModuleId}) {
+  _toModuleTransport({
+    module,
+    bundle,
+    entryFilePath,
+    transformOptions,
+    getModuleId,
+    dependencyPairs,
+  }) {
     let moduleTransport;
     const moduleId = getModuleId(module);
 
@@ -566,7 +579,7 @@ class Bundler {
         id: moduleId,
         code,
         map,
-        meta: {dependencies, dependencyOffsets, preloaded},
+        meta: {dependencies, dependencyOffsets, preloaded, dependencyPairs},
         sourceCode: source,
         sourcePath: module.path
       });

react-packager/src/Server/index.js

@@ -22,11 +22,18 @@ const mime = require('mime-types');
 const path = require('path');
 const url = require('url');
 
-function debounce(fn, delay) {
+const debug = require('debug')('ReactNativePackager:Server');
-  var timeout;
+
-  return () => {
+function debounceAndBatch(fn, delay) {
+  let timeout, args = [];
+  return (value) => {
+    args.push(value);
     clearTimeout(timeout);
-    timeout = setTimeout(fn, delay);
+    timeout = setTimeout(() => {
+      const a = args;
+      args = [];
+      fn(a);
+    }, delay);
   };
 }
 
@@ -139,7 +146,10 @@ const bundleOpts = declareOpts({
   isolateModuleIDs: {
     type: 'boolean',
     default: false
-  }
+  },
+  resolutionResponse: {
+    type: 'object',
+  },
 });
 
 const dependencyOpts = declareOpts({
@@ -163,8 +173,14 @@ const dependencyOpts = declareOpts({
     type: 'boolean',
     default: false,
   },
+  minify: {
+    type: 'boolean',
+    default: undefined,
+  },
 });
 
+const bundleDeps = new WeakMap();
+
 class Server {
   constructor(options) {
     const opts = validateOpts(options);
@@ -209,12 +225,27 @@ class Server {
     const bundlerOpts = Object.create(opts);
     bundlerOpts.fileWatcher = this._fileWatcher;
     bundlerOpts.assetServer = this._assetServer;
+    bundlerOpts.allowBundleUpdates = !options.nonPersistent;
     this._bundler = new Bundler(bundlerOpts);
 
     this._fileWatcher.on('all', this._onFileChange.bind(this));
 
-    this._debouncedFileChangeHandler = debounce(filePath => {
+    this._debouncedFileChangeHandler = debounceAndBatch(filePaths => {
+      // only clear bundles for non-JS changes
+      if (filePaths.every(RegExp.prototype.test, /\.js(?:on)?$/i)) {
+        for (const key in this._bundles) {
+          this._bundles[key].then(bundle => {
+            const deps = bundleDeps.get(bundle);
+            filePaths.forEach(filePath => {
+              if (deps.files.has(filePath)) {
+                deps.outdated.add(filePath);
+              }
+            });
+          });
+        }
+      } else {
         this._clearBundles();
+      }
       this._informChangeWatchers();
     }, 50);
   }
@@ -243,7 +274,26 @@ class Server {
       }
 
       const opts = bundleOpts(options);
-      return this._bundler.bundle(opts);
+      const building = this._bundler.bundle(opts);
+      building.then(bundle => {
+        const modules = bundle.getModules();
+        const nonVirtual = modules.filter(m => !m.virtual);
+        bundleDeps.set(bundle, {
+          files: new Map(
+            nonVirtual
+              .map(({sourcePath, meta = {dependencies: []}}) =>
+                [sourcePath, meta.dependencies])
+          ),
+          idToIndex: new Map(modules.map(({id}, i) => [id, i])),
+          dependencyPairs: new Map(
+            nonVirtual
+              .filter(({meta}) => meta && meta.dependencyPairs)
+              .map(m => [m.sourcePath, m.meta.dependencyPairs])
+          ),
+          outdated: new Set(),
+        });
+      });
+      return building;
     });
   }
 
@@ -428,6 +478,91 @@ class Server {
       ).done(() => Activity.endEvent(assetEvent));
   }
 
+  _useCachedOrUpdateOrCreateBundle(options) {
+    const optionsJson = JSON.stringify(options);
+    const bundleFromScratch = () => {
+      const building = this.buildBundle(options);
+      this._bundles[optionsJson] = building;
+      return building;
+    };
+
+    if (optionsJson in this._bundles) {
+      return this._bundles[optionsJson].then(bundle => {
+        const deps = bundleDeps.get(bundle);
+        const {dependencyPairs, files, idToIndex, outdated} = deps;
+        if (outdated.size) {
+          debug('Attempt to update existing bundle');
+          const changedModules =
+            Array.from(outdated, this.getModuleForPath, this);
+          deps.outdated = new Set();
+
+          const opts = bundleOpts(options);
+          const {platform, dev, minify, hot} = opts;
+
+          // Need to create a resolution response to pass to the bundler
+          // to process requires after transform. By providing a
+          // specific response we can compute a non recursive one which
+          // is the least we need and improve performance.
+          const bundlePromise = this._bundles[optionsJson] =
+            this.getDependencies({
+              platform, dev, hot, minify,
+              entryFile: options.entryFile,
+              recursive: false,
+            }).then(response => {
+              debug('Update bundle: rebuild shallow bundle');
+
+              changedModules.forEach(m => {
+                response.setResolvedDependencyPairs(
+                  m,
+                  dependencyPairs.get(m.path),
+                  {ignoreFinalized: true},
+                );
+              });
+
+              return this.buildBundle({
+                ...options,
+                resolutionResponse: response.copy({
+                  dependencies: changedModules,
+                })
+              }).then(updateBundle => {
+                const oldModules = bundle.getModules();
+                const newModules = updateBundle.getModules();
+                for (let i = 0, n = newModules.length; i < n; i++) {
+                  const moduleTransport = newModules[i];
+                  const {meta, sourcePath} = moduleTransport;
+                  if (outdated.has(sourcePath)) {
+                    if (!contentsEqual(meta.dependencies, new Set(files.get(sourcePath)))) {
+                      // bail out if any dependencies changed
+                      return Promise.reject(Error(
+                        `Dependencies of ${sourcePath} changed from [${
+                          files.get(sourcePath).join(', ')
+                        }] to [${meta.dependencies.join(', ')}]`
+                      ));
+                    }
+
+                    oldModules[idToIndex.get(moduleTransport.id)] = moduleTransport;
+                  }
+                }
+
+                bundle.invalidateSource();
+                debug('Successfully updated existing bundle');
+                return bundle;
+            });
+          }).catch(e => {
+            debug('Failed to update existing bundle, rebuilding...', e.stack || e.message);
+            return bundleFromScratch();
+          });
+          return bundlePromise;
+        } else {
+          debug('Using cached bundle');
+          return bundle;
+        }
+      });
+    }
+
+    return bundleFromScratch();
+  }
+
   processRequest(req, res, next) {
     const urlObj = url.parse(req.url, true);
     const pathname = urlObj.pathname;
@@ -458,26 +593,29 @@ class Server {
 
     const startReqEventId = Activity.startEvent('request:' + req.url);
     const options = this._getOptionsFromUrl(req.url);
-    const optionsJson = JSON.stringify(options);
+    debug('Getting bundle for request');
-    const building = this._bundles[optionsJson] || this.buildBundle(options);
+    const building = this._useCachedOrUpdateOrCreateBundle(options);
-
-    this._bundles[optionsJson] = building;
     building.then(
       p => {
         if (requestType === 'bundle') {
+          debug('Generating source code');
           const bundleSource = p.getSource({
             inlineSourceMap: options.inlineSourceMap,
             minify: options.minify,
             dev: options.dev,
           });
+          debug('Writing response headers');
           res.setHeader('Content-Type', 'application/javascript');
           res.setHeader('ETag', p.getEtag());
           if (req.headers['if-none-match'] === res.getHeader('ETag')){
+            debug('Responding with 304');
             res.statusCode = 304;
             res.end();
           } else {
+            debug('Writing request body');
             res.end(bundleSource);
           }
+          debug('Finished response');
           Activity.endEvent(startReqEventId);
         } else if (requestType === 'map') {
           let sourceMap = p.getSourceMap({
@@ -499,7 +637,7 @@ class Server {
           Activity.endEvent(startReqEventId);
         }
       },
-      this._handleError.bind(this, res, optionsJson)
+      error => this._handleError(res, JSON.stringify(options), error)
     ).done();
   }
 
@@ -564,9 +702,7 @@ class Server {
 
   _sourceMapForURL(reqUrl) {
     const options = this._getOptionsFromUrl(reqUrl);
-    const optionsJson = JSON.stringify(options);
+    const building = this._useCachedOrUpdateOrCreateBundle(options);
-    const building = this._bundles[optionsJson] || this.buildBundle(options);
-    this._bundles[optionsJson] = building;
     return building.then(p => {
       const sourceMap = p.getSourceMap({
         minify: options.minify,
@@ -659,4 +795,8 @@ class Server {
   }
 }
 
+function contentsEqual(array, set) {
+  return array.length === set.size && array.every(set.has, set);
+}
+
 module.exports = Server;

react-packager/src/node-haste/DependencyGraph/ResolutionResponse.js

@@ -8,6 +8,8 @@
  */
 'use strict';
 
+const NO_OPTIONS = {};
+
 class ResolutionResponse {
   constructor({transformOptions}) {
     this.transformOptions = transformOptions;
@@ -76,8 +78,10 @@ class ResolutionResponse {
     this.numPrependedDependencies += 1;
   }
 
-  setResolvedDependencyPairs(module, pairs) {
+  setResolvedDependencyPairs(module, pairs, options = NO_OPTIONS) {
+    if (!options.ignoreFinalized) {
       this._assertNotFinalized();
+    }
     const hash = module.hash();
     if (this._mappings[hash] == null) {
       this._mappings[hash] = pairs;