From e05b105dc6f5ee924dd963365ff3a83f49b5ca0b Mon Sep 17 00:00:00 2001
From: Jeffrey Posnick <jeffy@google.com>
Date: Thu, 3 Dec 2020 11:06:19 -0500
Subject: [PATCH] Preserve symbols across builds, don't mangle _handle (#2687)

* Preserve symbols across builds

* let => const
---
 gulp-tasks/build-packages.js        | 5 +++--
 gulp-tasks/build-sw-packages.js     | 4 +++-
 gulp-tasks/build-window-packages.js | 4 +++-
 gulp-tasks/utils/rollup-helper.js   | 8 +++++++-
 4 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/gulp-tasks/build-packages.js b/gulp-tasks/build-packages.js
index 071ab8c54..8fe014ca8 100644
--- a/gulp-tasks/build-packages.js
+++ b/gulp-tasks/build-packages.js
@@ -60,8 +60,9 @@ module.exports = {
       parallel(
           build_node_packages,
           build_node_ts_packages,
-          build_sw_packages,
-          build_window_packages,
+          // This needs to be a series, not in parallel, so that there isn't a
+          // race condition with the terser nameCache.
+          series(build_sw_packages, build_window_packages),
       ),
   ),
 };
diff --git a/gulp-tasks/build-sw-packages.js b/gulp-tasks/build-sw-packages.js
index d865065a8..ed4139623 100644
--- a/gulp-tasks/build-sw-packages.js
+++ b/gulp-tasks/build-sw-packages.js
@@ -158,7 +158,9 @@ function swBundleSequence() {
 
   return series(
       parallel(transpilations),
-      parallel(builds),
+      // This needs to be a series, not in parallel, so that there isn't a
+      // race condition with the terser nameCache.
+      series(builds),
   );
 }
 
diff --git a/gulp-tasks/build-window-packages.js b/gulp-tasks/build-window-packages.js
index 863874b03..b7d34eb66 100644
--- a/gulp-tasks/build-window-packages.js
+++ b/gulp-tasks/build-window-packages.js
@@ -102,7 +102,9 @@ function windowBundleSequence() {
 
   return series(
       parallel(transpilations),
-      parallel(builds),
+      // This needs to be a series, not in parallel, so that there isn't a
+      // race condition with the terser nameCache.
+      series(builds),
   );
 }
 
diff --git a/gulp-tasks/utils/rollup-helper.js b/gulp-tasks/utils/rollup-helper.js
index 39862887b..9ae9919ce 100644
--- a/gulp-tasks/utils/rollup-helper.js
+++ b/gulp-tasks/utils/rollup-helper.js
@@ -15,6 +15,9 @@ const terserPlugin = require('rollup-plugin-terser').terser;
 const constants = require('./constants');
 const getVersionsCDNUrl = require('./versioned-cdn-url');
 
+// See https://github.com/GoogleChrome/workbox/issues/1674
+const nameCache = {};
+
 module.exports = {
   // Every use of rollup should have minification and the replace
   // plugin set up and used to ensure as consist set of tests
@@ -46,6 +49,7 @@ module.exports = {
     const minifyBuild = buildType === constants.BUILD_TYPES.prod;
     if (minifyBuild) {
       const terserOptions = {
+        nameCache,
         module: buildFormat === 'esm' ? true : false,
         mangle: {
           properties: {
@@ -54,8 +58,10 @@ module.exports = {
               '_obj',
               // We need this to be exported correctly.
               '_private',
+              // See https://github.com/GoogleChrome/workbox/issues/2686
+              '_handle',
             ],
-            // mangle > properties > regex will allow uglify-es to minify
+            // mangle > properties > regex will allow terser to minify
             // private variable and names that start with a single underscore
             // followed by a letter. This restriction to avoid mangling
             // unintentional fields in our or other libraries code.