From 634ab4509539d566a3cebf985ad18ff14f9fbc2a Mon Sep 17 00:00:00 2001
From: Samuel Attard <sattard@slack-corp.com>
Date: Mon, 1 Jun 2020 16:08:34 -0700
Subject: [PATCH] build: make electron renderer init scripts profilable
 (#23855)

The devtools profiler is not attached at the point we run out init scripts (or our apps preload scripts), we do not really want to change when we run these init scripts but for when a dev is doing performance work it makes sense to give them an option to make the devtools profiler actually work on both our init scripts and their preload script.  This PR adds that logic behind an environment variable ELECTRON_PROFILE_INIT_SCRIPTS.
---
 build/webpack/run-compiler.js                    | 16 ++++++++++++++++
 build/webpack/webpack.config.base.js             |  4 +++-
 build/webpack/webpack.config.renderer.js         |  3 ++-
 .../webpack/webpack.config.sandboxed_renderer.js |  3 ++-
 build/webpack/webpack.gni                        |  1 +
 shell/browser/electron_browser_client.cc         |  5 +++++
 6 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/build/webpack/run-compiler.js b/build/webpack/run-compiler.js
index 0b3b7735743a..9aa75e7bf549 100644
--- a/build/webpack/run-compiler.js
+++ b/build/webpack/run-compiler.js
@@ -1,3 +1,4 @@
+const fs = require('fs');
 const path = require('path')
 const webpack = require('webpack')
 
@@ -9,6 +10,9 @@ config.output = {
   filename: path.basename(outPath)
 }
 
+const { wrapInitWithProfilingTimeout } = config;
+delete config.wrapInitWithProfilingTimeout;
+
 webpack(config, (err, stats) => {
   if (err) {
     console.error(err)
@@ -17,6 +21,18 @@ webpack(config, (err, stats) => {
     console.error(stats.toString('normal'))
     process.exit(1)
   } else {
+    if (wrapInitWithProfilingTimeout) {
+      const contents = fs.readFileSync(outPath, 'utf8');
+      const newContents = `function ___electron_webpack_init__() {
+${contents}
+};
+if ((globalThis.process || binding.process).argv.includes("--profile-electron-init")) {
+  setTimeout(___electron_webpack_init__, 0);
+} else {
+  ___electron_webpack_init__();
+}`;
+      fs.writeFileSync(outPath, newContents);
+    }
     process.exit(0)
   }
 })
diff --git a/build/webpack/webpack.config.base.js b/build/webpack/webpack.config.base.js
index 88fc50dfb555..a51df60d61ec 100644
--- a/build/webpack/webpack.config.base.js
+++ b/build/webpack/webpack.config.base.js
@@ -67,7 +67,8 @@ module.exports = ({
   alwaysHasNode,
   loadElectronFromAlternateTarget,
   targetDeletesNodeGlobals,
-  target
+  target,
+  wrapInitWithProfilingTimeout
 }) => {
   let entry = path.resolve(electronRoot, 'lib', target, 'init.ts')
   if (!fs.existsSync(entry)) {
@@ -82,6 +83,7 @@ module.exports = ({
     output: {
       filename: `${target}.bundle.js`
     },
+    wrapInitWithProfilingTimeout,
     resolve: {
       alias: {
         '@electron/internal': path.resolve(electronRoot, 'lib'),
diff --git a/build/webpack/webpack.config.renderer.js b/build/webpack/webpack.config.renderer.js
index 391254d14240..8f890ee6e0d7 100644
--- a/build/webpack/webpack.config.renderer.js
+++ b/build/webpack/webpack.config.renderer.js
@@ -1,5 +1,6 @@
 module.exports = require('./webpack.config.base')({
   target: 'renderer',
   alwaysHasNode: true,
-  targetDeletesNodeGlobals: true
+  targetDeletesNodeGlobals: true,
+  wrapInitWithProfilingTimeout: true
 })
diff --git a/build/webpack/webpack.config.sandboxed_renderer.js b/build/webpack/webpack.config.sandboxed_renderer.js
index 0ca65254ddfc..9c38d6acb99b 100644
--- a/build/webpack/webpack.config.sandboxed_renderer.js
+++ b/build/webpack/webpack.config.sandboxed_renderer.js
@@ -1,4 +1,5 @@
 module.exports = require('./webpack.config.base')({
   target: 'sandboxed_renderer',
-  alwaysHasNode: false
+  alwaysHasNode: false,
+  wrapInitWithProfilingTimeout: true,
 })
diff --git a/build/webpack/webpack.gni b/build/webpack/webpack.gni
index 38699a18bd2e..ade1fe78e07b 100644
--- a/build/webpack/webpack.gni
+++ b/build/webpack/webpack.gni
@@ -16,6 +16,7 @@ template("webpack_build") {
     inputs = [
                invoker.config_file,
                "//electron/build/webpack/webpack.config.base.js",
+               "//electron/build/webpack/run-compiler.js",
                "//electron/tsconfig.json",
                "//electron/yarn.lock",
                "//electron/typings/internal-ambient.d.ts",
diff --git a/shell/browser/electron_browser_client.cc b/shell/browser/electron_browser_client.cc
index 14bdb8b0798e..fbcf14846468 100644
--- a/shell/browser/electron_browser_client.cc
+++ b/shell/browser/electron_browser_client.cc
@@ -766,6 +766,11 @@ void ElectronBrowserClient::AppendExtraCommandLineSwitches(
       command_line->AppendSwitchPath(switches::kAppPath, app_path);
     }
 
+    std::unique_ptr<base::Environment> env(base::Environment::Create());
+    if (env->HasVar("ELECTRON_PROFILE_INIT_SCRIPTS")) {
+      command_line->AppendSwitch("profile-electron-init");
+    }
+
     content::WebContents* web_contents =
         GetWebContentsFromProcessID(process_id);
     if (web_contents) {