From a1fd612b4c3f74238e75b353b2bf901f128b7ca2 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 21 Dec 2016 20:29:54 +0100
Subject: [PATCH 1/6] Fix captureJSCallUsage in the face of Error polyfills.
 (error.stack is overwritten)

V8 has the property prepareStackTrace on errors where you can format a stacktrace. This only works on native errors not on custom ones.
---
 lighthouse-core/gather/driver.js        | 14 ++++++++------
 lighthouse-core/gather/gather-runner.js |  3 ++-
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/lighthouse-core/gather/driver.js b/lighthouse-core/gather/driver.js
index 155a4b8c81ae..28fa946a33cc 100644
--- a/lighthouse-core/gather/driver.js
+++ b/lighthouse-core/gather/driver.js
@@ -701,7 +701,7 @@ class Driver {
 
     this.evaluateScriptOnLoad(`
         ${globalVarToPopulate} = new Set();
-        (${funcName} = ${funcBody}(${funcName}, ${globalVarToPopulate}))`);
+        (${funcName} = ${funcBody}(${funcName}, ${globalVarToPopulate}, window.__nativeError))`);
 
     return collectUsage;
   }
@@ -712,11 +712,13 @@ class Driver {
  * @param {function(...*): *} funcRef The function call to track.
  * @param {!Set} set An empty set to populate with stack traces. Should be
  *     on the global object.
+ * @param {Error} nativeError The origal error object some libraries overwrite it.
+ *     So they can take full control of errors.
  * @return {function(...*): *} A wrapper around the original function.
  */
-function captureJSCallUsage(funcRef, set) {
+function captureJSCallUsage(funcRef, set, NativeError) {
   const originalFunc = funcRef;
-  const originalPrepareStackTrace = Error.prepareStackTrace;
+  const originalPrepareStackTrace = nativeError.prepareStackTrace;
 
   return function() {
     // Note: this function runs in the context of the page that is being audited.
@@ -724,7 +726,7 @@ function captureJSCallUsage(funcRef, set) {
     const args = [...arguments]; // callee's arguments.
 
     // See v8's Stack Trace API https://github.com/v8/v8/wiki/Stack-Trace-API#customizing-stack-traces
-    Error.prepareStackTrace = function(error, structStackTrace) {
+    NativeError.prepareStackTrace = function(error, structStackTrace) {
       // First frame is the function we injected (the one that just threw).
       // Second, is the actual callsite of the funcRef we're after.
       const callFrame = structStackTrace[1];
@@ -747,12 +749,12 @@ function captureJSCallUsage(funcRef, set) {
       // would be unique.
       return {url, args, line, col, isEval}; // return value is e.stack
     };
-    const e = new Error(`__called ${funcRef.name}__`);
+    const e = new NativeError(`__called ${funcRef.name}__`);
     set.add(JSON.stringify(e.stack));
 
     // Restore prepareStackTrace so future errors use v8's formatter and not
     // our custom one.
-    Error.prepareStackTrace = originalPrepareStackTrace;
+    NativeError.prepareStackTrace = originalPrepareStackTrace;
 
     // eslint-disable-next-line no-invalid-this
     return originalFunc.apply(this, arguments);
diff --git a/lighthouse-core/gather/gather-runner.js b/lighthouse-core/gather/gather-runner.js
index ae7286670fdf..33977d0d4cd6 100644
--- a/lighthouse-core/gather/gather-runner.js
+++ b/lighthouse-core/gather/gather-runner.js
@@ -94,7 +94,8 @@ class GatherRunner {
     return driver.assertNoSameOriginServiceWorkerClients(options.url)
       .then(_ => driver.beginEmulation(options.flags))
       .then(_ => driver.enableRuntimeEvents())
-      .then(_ => driver.evaluateScriptOnLoad('window.__nativePromise = Promise;'))
+      .then(_ => driver.evaluateScriptOnLoad(`window.__nativePromise = Promise;
+        window.__nativeError = Error;`))
       .then(_ => driver.cleanAndDisableBrowserCaches())
       .then(_ => driver.clearDataForOrigin(options.url));
   }

From 01ec31bda4bc20999cd4a5a693daca7211750f94 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 21 Dec 2016 21:08:54 +0100
Subject: [PATCH 2/6] Add dbw test

---
 lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html b/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html
index 2834f982da3c..aeb7269fcd24 100644
--- a/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html
+++ b/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html
@@ -88,6 +88,7 @@ <h2>Do better web tester page</h2>
   <a href="./doesnotexist" target="_blank">internal link is ok</a>
 </template>
 
+<script>window.Error = function(error) { this.stack = 'stacktrace'; };</script>
 <script>
 function stampTemplate(id, location) {
   const template = document.querySelector('#' + id);

From 5759a3cc0ee4ecafce4149e473249c1e8dbe2a81 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 21 Dec 2016 21:10:31 +0100
Subject: [PATCH 3/6] Fix typos

---
 lighthouse-core/gather/driver.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lighthouse-core/gather/driver.js b/lighthouse-core/gather/driver.js
index 28fa946a33cc..86fab4dfba2d 100644
--- a/lighthouse-core/gather/driver.js
+++ b/lighthouse-core/gather/driver.js
@@ -712,13 +712,13 @@ class Driver {
  * @param {function(...*): *} funcRef The function call to track.
  * @param {!Set} set An empty set to populate with stack traces. Should be
  *     on the global object.
- * @param {Error} nativeError The origal error object some libraries overwrite it.
+ * @param {Error} NativeError The origal error object some libraries overwrite it.
  *     So they can take full control of errors.
  * @return {function(...*): *} A wrapper around the original function.
  */
 function captureJSCallUsage(funcRef, set, NativeError) {
   const originalFunc = funcRef;
-  const originalPrepareStackTrace = nativeError.prepareStackTrace;
+  const originalPrepareStackTrace = NativeError.prepareStackTrace;
 
   return function() {
     // Note: this function runs in the context of the page that is being audited.

From e09170c073e337d8f88f03b77f29eee9c2cba9e9 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 21 Dec 2016 21:11:31 +0100
Subject: [PATCH 4/6] More typo :(

---
 lighthouse-core/gather/driver.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lighthouse-core/gather/driver.js b/lighthouse-core/gather/driver.js
index 86fab4dfba2d..6def2cc621a9 100644
--- a/lighthouse-core/gather/driver.js
+++ b/lighthouse-core/gather/driver.js
@@ -712,7 +712,7 @@ class Driver {
  * @param {function(...*): *} funcRef The function call to track.
  * @param {!Set} set An empty set to populate with stack traces. Should be
  *     on the global object.
- * @param {Error} NativeError The origal error object some libraries overwrite it.
+ * @param {Error} NativeError The original error object some libraries overwrite it.
  *     So they can take full control of errors.
  * @return {function(...*): *} A wrapper around the original function.
  */

From b345737f33eeecb58f2995af3a15bdf1fea243a7 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 21 Dec 2016 22:00:13 +0100
Subject: [PATCH 5/6] Added documentation to dbw test

---
 lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html b/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html
index aeb7269fcd24..f73a4b5748e0 100644
--- a/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html
+++ b/lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html
@@ -88,6 +88,10 @@ <h2>Do better web tester page</h2>
   <a href="./doesnotexist" target="_blank">internal link is ok</a>
 </template>
 
+<!-- Some websites overwrite the original Error object. The captureJSCallUsage function
+  relies on the native Error object and prepareStackTrace from V8. When overwriting the stack
+  property the e.stack inside the gatherer won't be in the correct format
+  https://github.com/GoogleChrome/lighthouse/issues/1194 -->
 <script>window.Error = function(error) { this.stack = 'stacktrace'; };</script>
 <script>
 function stampTemplate(id, location) {

From 83170c144b1b48325ceb02dd0d1099be2a651284 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 21 Dec 2016 22:14:08 +0100
Subject: [PATCH 6/6] Review changes

---
 lighthouse-core/gather/driver.js              | 24 ++++++++++++-------
 lighthouse-core/gather/gather-runner.js       |  3 +--
 lighthouse-core/test/gather/fake-driver.js    |  3 +++
 .../test/gather/gather-runner-test.js         |  3 +++
 4 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/lighthouse-core/gather/driver.js b/lighthouse-core/gather/driver.js
index 6def2cc621a9..d9c37a0c4a32 100644
--- a/lighthouse-core/gather/driver.js
+++ b/lighthouse-core/gather/driver.js
@@ -675,6 +675,15 @@ class Driver {
     });
   }
 
+  /**
+   * Cache native functions/objects inside window
+   * so we are sure polyfills do not overwrite the native implementations
+   */
+  cacheNatives() {
+    return this.evaluateScriptOnLoad(`window.__nativePromise = Promise;
+        window.__nativeError = Error;`);
+  }
+
   /**
    * Keeps track of calls to a JS function and returns a list of {url, line, col}
    * of the usage. Should be called before page load (in beforePass).
@@ -701,7 +710,7 @@ class Driver {
 
     this.evaluateScriptOnLoad(`
         ${globalVarToPopulate} = new Set();
-        (${funcName} = ${funcBody}(${funcName}, ${globalVarToPopulate}, window.__nativeError))`);
+        (${funcName} = ${funcBody}(${funcName}, ${globalVarToPopulate}))`);
 
     return collectUsage;
   }
@@ -712,13 +721,12 @@ class Driver {
  * @param {function(...*): *} funcRef The function call to track.
  * @param {!Set} set An empty set to populate with stack traces. Should be
  *     on the global object.
- * @param {Error} NativeError The original error object some libraries overwrite it.
- *     So they can take full control of errors.
  * @return {function(...*): *} A wrapper around the original function.
  */
-function captureJSCallUsage(funcRef, set, NativeError) {
+function captureJSCallUsage(funcRef, set) {
+  const __nativeError = window.__nativeError || Error;
   const originalFunc = funcRef;
-  const originalPrepareStackTrace = NativeError.prepareStackTrace;
+  const originalPrepareStackTrace = __nativeError.prepareStackTrace;
 
   return function() {
     // Note: this function runs in the context of the page that is being audited.
@@ -726,7 +734,7 @@ function captureJSCallUsage(funcRef, set, NativeError) {
     const args = [...arguments]; // callee's arguments.
 
     // See v8's Stack Trace API https://github.com/v8/v8/wiki/Stack-Trace-API#customizing-stack-traces
-    NativeError.prepareStackTrace = function(error, structStackTrace) {
+    __nativeError.prepareStackTrace = function(error, structStackTrace) {
       // First frame is the function we injected (the one that just threw).
       // Second, is the actual callsite of the funcRef we're after.
       const callFrame = structStackTrace[1];
@@ -749,12 +757,12 @@ function captureJSCallUsage(funcRef, set, NativeError) {
       // would be unique.
       return {url, args, line, col, isEval}; // return value is e.stack
     };
-    const e = new NativeError(`__called ${funcRef.name}__`);
+    const e = new __nativeError(`__called ${funcRef.name}__`);
     set.add(JSON.stringify(e.stack));
 
     // Restore prepareStackTrace so future errors use v8's formatter and not
     // our custom one.
-    NativeError.prepareStackTrace = originalPrepareStackTrace;
+    __nativeError.prepareStackTrace = originalPrepareStackTrace;
 
     // eslint-disable-next-line no-invalid-this
     return originalFunc.apply(this, arguments);
diff --git a/lighthouse-core/gather/gather-runner.js b/lighthouse-core/gather/gather-runner.js
index 33977d0d4cd6..cb5df112afb6 100644
--- a/lighthouse-core/gather/gather-runner.js
+++ b/lighthouse-core/gather/gather-runner.js
@@ -94,8 +94,7 @@ class GatherRunner {
     return driver.assertNoSameOriginServiceWorkerClients(options.url)
       .then(_ => driver.beginEmulation(options.flags))
       .then(_ => driver.enableRuntimeEvents())
-      .then(_ => driver.evaluateScriptOnLoad(`window.__nativePromise = Promise;
-        window.__nativeError = Error;`))
+      .then(_ => driver.cacheNatives())
       .then(_ => driver.cleanAndDisableBrowserCaches())
       .then(_ => driver.clearDataForOrigin(options.url));
   }
diff --git a/lighthouse-core/test/gather/fake-driver.js b/lighthouse-core/test/gather/fake-driver.js
index 8ecc48c59a3b..438499ef4350 100644
--- a/lighthouse-core/test/gather/fake-driver.js
+++ b/lighthouse-core/test/gather/fake-driver.js
@@ -43,6 +43,9 @@ module.exports = {
   },
   cleanAndDisableBrowserCaches() {},
   clearDataForOrigin() {},
+  cacheNatives() {
+    return Promise.resolve();
+  },
   beginTrace() {
     return Promise.resolve();
   },
diff --git a/lighthouse-core/test/gather/gather-runner-test.js b/lighthouse-core/test/gather/gather-runner-test.js
index 3bc02caab1e0..5f64e62baec2 100644
--- a/lighthouse-core/test/gather/gather-runner-test.js
+++ b/lighthouse-core/test/gather/gather-runner-test.js
@@ -54,6 +54,9 @@ function getMockedEmulationDriver(emulationFn, netThrottleFn, cpuThrottleFn) {
     assertNoSameOriginServiceWorkerClients() {
       return Promise.resolve();
     }
+    cacheNatives() {
+      return Promise.resolve();
+    }
     cleanAndDisableBrowserCaches() {}
     clearDataForOrigin() {}
   };