From 1ab6091aa5a9ffe639a1c1e31805e9621851e2bd Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Tue, 31 Dec 2019 13:53:52 -0500
Subject: [PATCH] fix(@angular-devkit/build-angular): prevent differential
 loading double sourcemap search

This can drastically reduce memory usage; especially in cases where bundled code modules contain individual sourcemap comments and vendor sourcemaps are disabled.  Enabling the vendor sourcemap option has the side effect of removing all individual module sourcemap comments and as a result removes the potential for those comments to be found and processed.
---
 .../angular_devkit/build_angular/src/utils/process-bundle.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/packages/angular_devkit/build_angular/src/utils/process-bundle.ts b/packages/angular_devkit/build_angular/src/utils/process-bundle.ts
index 730226ad83b7..2fe4b34ade59 100644
--- a/packages/angular_devkit/build_angular/src/utils/process-bundle.ts
+++ b/packages/angular_devkit/build_angular/src/utils/process-bundle.ts
@@ -97,7 +97,7 @@ export async function process(options: ProcessBundleOptions): Promise<ProcessBun
   const manualSourceMaps = codeSize >= 1024 * 1024 || mapSize >= 1024 * 1024;
 
   const sourceCode = options.code;
-  const sourceMap = options.map ? JSON.parse(options.map) : undefined;
+  const sourceMap = options.map ? JSON.parse(options.map) : false;
 
   let downlevelCode;
   let downlevelMap;
@@ -105,7 +105,8 @@ export async function process(options: ProcessBundleOptions): Promise<ProcessBun
     // Downlevel the bundle
     const transformResult = await transformAsync(sourceCode, {
       filename: options.filename,
-      inputSourceMap: manualSourceMaps ? undefined : sourceMap,
+      // using false ensures that babel will NOT search and process sourcemap comments (large memory usage)
+      inputSourceMap: manualSourceMaps ? false : sourceMap,
       babelrc: false,
       presets: [
         [