From 05f877e384520dbcaf190c7add9a33425e857ad0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20Og=C3=B3rek?= <kamil.ogorek@gmail.com>
Date: Thu, 4 Jun 2020 14:47:15 +0200
Subject: [PATCH 1/3] Change XHR instrumentation ordering

---
 packages/utils/src/instrument.ts | 40 +++++++++++++++-----------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/packages/utils/src/instrument.ts b/packages/utils/src/instrument.ts
index f4880b5fa229..ee15cb47f552 100644
--- a/packages/utils/src/instrument.ts
+++ b/packages/utils/src/instrument.ts
@@ -218,34 +218,18 @@ function instrumentXHR(): void {
 
   fill(xhrproto, 'open', function(originalOpen: () => void): () => void {
     return function(this: SentryWrappedXMLHttpRequest, ...args: any[]): void {
+      const xhr = this; // tslint:disable-line:no-this-assignment
       const url = args[1];
-      this.__sentry_xhr__ = {
+      xhr.__sentry_xhr__ = {
         method: isString(args[0]) ? args[0].toUpperCase() : args[0],
         url: args[1],
       };
 
       // if Sentry key appears in URL, don't capture it as a request
-      if (isString(url) && this.__sentry_xhr__.method === 'POST' && url.match(/sentry_key/)) {
-        this.__sentry_own_request__ = true;
+      if (isString(url) && xhr.__sentry_xhr__.method === 'POST' && url.match(/sentry_key/)) {
+        xhr.__sentry_own_request__ = true;
       }
 
-      return originalOpen.apply(this, args);
-    };
-  });
-
-  fill(xhrproto, 'send', function(originalSend: () => void): () => void {
-    return function(this: SentryWrappedXMLHttpRequest, ...args: any[]): void {
-      const xhr = this; // tslint:disable-line:no-this-assignment
-      const commonHandlerData = {
-        args,
-        startTimestamp: Date.now(),
-        xhr,
-      };
-
-      triggerHandlers('xhr', {
-        ...commonHandlerData,
-      });
-
       xhr.addEventListener('readystatechange', function(): void {
         if (xhr.readyState === 4) {
           try {
@@ -258,12 +242,26 @@ function instrumentXHR(): void {
             /* do nothing */
           }
           triggerHandlers('xhr', {
-            ...commonHandlerData,
+            args,
             endTimestamp: Date.now(),
+            startTimestamp: Date.now(),
+            xhr,
           });
         }
       });
 
+      return originalOpen.apply(xhr, args);
+    };
+  });
+
+  fill(xhrproto, 'send', function(originalSend: () => void): () => void {
+    return function(this: SentryWrappedXMLHttpRequest, ...args: any[]): void {
+      triggerHandlers('xhr', {
+        args,
+        startTimestamp: Date.now(),
+        xhr: this,
+      });
+
       return originalSend.apply(this, args);
     };
   });

From 2eacf2be40271072edc3eaea9a7d7b1aba81ed23 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20Og=C3=B3rek?= <kamil.ogorek@gmail.com>
Date: Mon, 8 Jun 2020 12:00:19 +0200
Subject: [PATCH 2/3] Handle onreadystatechange attached before open was called

---
 packages/utils/src/instrument.ts | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/packages/utils/src/instrument.ts b/packages/utils/src/instrument.ts
index ee15cb47f552..6348111563c4 100644
--- a/packages/utils/src/instrument.ts
+++ b/packages/utils/src/instrument.ts
@@ -230,7 +230,7 @@ function instrumentXHR(): void {
         xhr.__sentry_own_request__ = true;
       }
 
-      xhr.addEventListener('readystatechange', function(): void {
+      const onreadystatechangeHandler = function(): void {
         if (xhr.readyState === 4) {
           try {
             // touching statusCode in some platforms throws
@@ -248,7 +248,18 @@ function instrumentXHR(): void {
             xhr,
           });
         }
-      });
+      };
+
+      if ('onreadystatechange' in xhr && typeof xhr.onreadystatechange === 'function') {
+        fill(xhr, 'onreadystatechange', function(original: WrappedFunction): Function {
+          return function(...readyStateArgs: any[]): void {
+            onreadystatechangeHandler();
+            return original.apply(xhr, readyStateArgs);
+          };
+        });
+      } else {
+        xhr.addEventListener('readystatechange', onreadystatechangeHandler);
+      }
 
       return originalOpen.apply(xhr, args);
     };

From 31e8e80ea767813c38f7ed766a8cea32c2395f1e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20Og=C3=B3rek?= <kamil.ogorek@gmail.com>
Date: Mon, 8 Jun 2020 12:07:45 +0200
Subject: [PATCH 3/3] Changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d14bf0d4c9af..c39c9ecb43c6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - "You miss 100 percent of the chances you don't take. — Wayne Gretzky" — Michael Scott
 - [react] feat: Add @sentry/react package (#2631)
+- [browser] Change XHR instrumentation order to handle `onreadystatechange` breadcrumbs correctly (#2643)
 
 ## 5.16.1