packager: TransformCache: do not rehash transformOptions every single time

Reviewed By: davidaurelio

Differential Revision: D4809963

fbshipit-source-id: 9d3ac907e822596567ee7af4427bcd24f1bac73f

packages/metro-bundler/src/lib/TransformCache.js

@@ -19,7 +19,6 @@ const fs = require('fs');
  * this particular use case.
  */
 const imurmurhash = require('imurmurhash');
-const jsonStableStringify = require('json-stable-stringify');
 const mkdirp = require('mkdirp');
 const path = require('path');
 const rimraf = require('rimraf');
@@ -64,6 +63,7 @@ function hashSourceCode(props: {
   sourceCode: string,
   getTransformCacheKey: GetTransformCacheKey,
   transformOptions: TransformOptions,
+  transformOptionsKey: string,
 }): string {
   return imurmurhash(props.getTransformCacheKey(
     props.sourceCode,
@@ -79,11 +79,11 @@ function hashSourceCode(props: {
  */
 function getCacheFilePaths(props: {
   filePath: string,
-  transformOptions: TransformOptions,
+  transformOptionsKey: string,
 }): CacheFilePaths {
   const hasher = imurmurhash()
     .hash(props.filePath)
-    .hash(jsonStableStringify(props.transformOptions) || '');
+    .hash(props.transformOptionsKey);
   const hash = toFixedHex(8, hasher.result());
   const prefix = hash.substr(0, 2);
   const fileName = `${hash.substr(2)}${path.basename(props.filePath)}`;
@@ -135,6 +135,7 @@ function writeSync(props: {
   sourceCode: string,
   getTransformCacheKey: GetTransformCacheKey,
   transformOptions: TransformOptions,
+  transformOptionsKey: string,
   result: CachedResult,
 }): void {
   const cacheFilePath = getCacheFilePaths(props);
@@ -296,6 +297,7 @@ export type ReadTransformProps = {
   filePath: string,
   sourceCode: string,
   transformOptions: TransformOptions,
+  transformOptionsKey: string,
   getTransformCacheKey: GetTransformCacheKey,
   cacheOptions: CacheOptions,
 };

packages/metro-bundler/src/lib/__tests__/TransformCache-test.js

@@ -15,9 +15,12 @@ jest
   .dontMock('../TransformCache')
   .dontMock('../toFixedHex')
   .dontMock('left-pad')
-  .dontMock('lodash/throttle');
+  .dontMock('lodash/throttle')
+  .dontMock('crypto');
 
 const imurmurhash = require('imurmurhash');
+const crypto = require('crypto');
+const jsonStableStringify = require('json-stable-stringify');
 
 const memoryFS = new Map();
 
@@ -66,6 +69,8 @@ describe('TransformCache', () => {
         getTransformCacheKey: () => 'abcdef',
         filePath,
         transformOptions,
+        transformOptionsKey: crypto.createHash('md5')
+          .update(jsonStableStringify(transformOptions)).digest('hex'),
         result: {
           code: `/* result for ${key} */`,
           dependencies: ['foo', `dep of ${key}`],
@@ -100,6 +105,7 @@ describe('TransformCache', () => {
         getTransformCacheKey: () => transformCacheKey,
         filePath: 'test.js',
         transformOptions: {foo: 1},
+        transformOptionsKey: 'boo!',
         result: {
           code: `/* result for ${key} */`,
           dependencies: ['foo', `dep of ${key}`],

packages/metro-bundler/src/node-haste/Module.js

@@ -360,7 +360,7 @@ class Module {
     if (this._readResultsByOptionsKey.has(key)) {
       return this._readResultsByOptionsKey.get(key);
     }
-    const result = this._readFromTransformCache(transformOptions);
+    const result = this._readFromTransformCache(transformOptions, key);
     this._readResultsByOptionsKey.set(key, result);
     return result;
   }
@@ -369,8 +369,11 @@ class Module {
    * Read again from the TransformCache, on disk. `readCached` should be favored
    * so it's faster in case the results are already in memory.
    */
-  _readFromTransformCache(transformOptions: TransformOptions): ?ReadResult {
-    const cacheProps = this._getCacheProps(transformOptions);
+  _readFromTransformCache(
+    transformOptions: TransformOptions,
+    transformOptionsKey: string,
+  ): ?ReadResult {
+    const cacheProps = this._getCacheProps(transformOptions, transformOptionsKey);
     const cachedResult = TransformCache.readSync(cacheProps);
     if (cachedResult) {
       return this._finalizeReadResult(cacheProps.sourceCode, cachedResult);
@@ -391,7 +394,7 @@ class Module {
       return promise;
     }
     const freshPromise = Promise.resolve().then(() => {
-      const cacheProps = this._getCacheProps(transformOptions);
+      const cacheProps = this._getCacheProps(transformOptions, key);
       return new Promise((resolve, reject) => {
         this._getAndCacheTransformedCode(
           cacheProps,
@@ -413,7 +416,7 @@ class Module {
     return freshPromise;
   }
 
-  _getCacheProps(transformOptions: TransformOptions) {
+  _getCacheProps(transformOptions: TransformOptions, transformOptionsKey: string) {
     const sourceCode = this._readSourceCode();
     const moduleDocBlock = this._readDocBlock();
     const getTransformCacheKey = this._getTransformCacheKey;
@@ -428,6 +431,7 @@ class Module {
       sourceCode,
       getTransformCacheKey,
       transformOptions,
+      transformOptionsKey,
       cacheOptions: {
         resetCache: this._options.resetCache,
         reporter: this._reporter,