From c7c6a5b1dde69515e92dbbc250e2624a6769b0e0 Mon Sep 17 00:00:00 2001
From: Luca Forstner <luca.forstner@sentry.io>
Date: Wed, 25 May 2022 09:22:03 +0000
Subject: [PATCH 1/3] fix(utils): Fix infinite recursion in `dropUndefinedKeys`

---
 packages/utils/src/object.ts       | 19 ++++++++++++--
 packages/utils/test/object.test.ts | 41 ++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/packages/utils/src/object.ts b/packages/utils/src/object.ts
index d4974cecbf44..0999b38192bc 100644
--- a/packages/utils/src/object.ts
+++ b/packages/utils/src/object.ts
@@ -4,6 +4,7 @@ import { WrappedFunction } from '@sentry/types';
 
 import { htmlTreeAsString } from './browser';
 import { isElement, isError, isEvent, isInstanceOf, isPlainObject, isPrimitive } from './is';
+import { memoBuilder, MemoFunc } from './memo';
 import { truncate } from './string';
 
 /**
@@ -207,18 +208,32 @@ export function extractExceptionKeysForMessage(exception: Record<string, unknown
  * Works recursively on objects and arrays.
  */
 export function dropUndefinedKeys<T>(val: T): T {
+  return _dropUndefinedKeys(val, memoBuilder());
+}
+
+function _dropUndefinedKeys<T>(val: T, memo: MemoFunc): T {
+  const [memoize] = memo;
+
   if (isPlainObject(val)) {
+    if (memoize(val)) {
+      return val;
+    }
     const rv: { [key: string]: any } = {};
     for (const key of Object.keys(val)) {
       if (typeof val[key] !== 'undefined') {
-        rv[key] = dropUndefinedKeys(val[key]);
+        rv[key] = _dropUndefinedKeys(val[key], memo);
       }
     }
     return rv as T;
   }
 
   if (Array.isArray(val)) {
-    return (val as any[]).map(dropUndefinedKeys) as any;
+    if (memoize(val)) {
+      return val;
+    }
+    return (val as any[]).map(item => {
+      return _dropUndefinedKeys(item, memo);
+    }) as any;
   }
 
   return val;
diff --git a/packages/utils/test/object.test.ts b/packages/utils/test/object.test.ts
index e4fc4428ae04..65131fa0cd94 100644
--- a/packages/utils/test/object.test.ts
+++ b/packages/utils/test/object.test.ts
@@ -199,6 +199,47 @@ describe('dropUndefinedKeys()', () => {
       },
     });
   });
+
+  test('objects with circular reference', () => {
+    const dog: any = {
+      food: undefined,
+    };
+
+    const human = {
+      brain: undefined,
+      pets: dog,
+    };
+
+    const rat = {
+      scares: human,
+      weight: '4kg',
+    };
+
+    dog.chases = rat;
+
+    expect(dropUndefinedKeys(human)).toStrictEqual({
+      pets: {
+        chases: rat,
+      },
+    });
+  });
+
+  test('arrays with circular reference', () => {
+    const egg: any[] = [];
+
+    const chicken = {
+      food: undefined,
+      weight: '1kg',
+      lays: egg,
+    };
+
+    egg[0] = chicken;
+
+    expect(dropUndefinedKeys(chicken)).toStrictEqual({
+      lays: egg,
+      weight: '1kg',
+    });
+  });
 });
 
 describe('objectify()', () => {

From 75373c15eb8eea2791f91c7c4e898952cedebcea Mon Sep 17 00:00:00 2001
From: Luca Forstner <luca.forstner@sentry.io>
Date: Wed, 25 May 2022 09:28:23 +0000
Subject: [PATCH 2/3] Add comments

---
 packages/utils/src/object.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/utils/src/object.ts b/packages/utils/src/object.ts
index 0999b38192bc..e9373797c44f 100644
--- a/packages/utils/src/object.ts
+++ b/packages/utils/src/object.ts
@@ -208,11 +208,12 @@ export function extractExceptionKeysForMessage(exception: Record<string, unknown
  * Works recursively on objects and arrays.
  */
 export function dropUndefinedKeys<T>(val: T): T {
+  // This function just proxies `_dropUndefinedKeys` to keep the `memoBuilder` out of this function's API
   return _dropUndefinedKeys(val, memoBuilder());
 }
 
 function _dropUndefinedKeys<T>(val: T, memo: MemoFunc): T {
-  const [memoize] = memo;
+  const [memoize] = memo; // we don't need unmemoize because we don't need to visit nodes twice
 
   if (isPlainObject(val)) {
     if (memoize(val)) {

From 4429b6433acad1481dbe0b8573cb6e4522ba2f0c Mon Sep 17 00:00:00 2001
From: Luca Forstner <luca.forstner@sentry.io>
Date: Wed, 25 May 2022 10:22:31 +0000
Subject: [PATCH 3/3] Add comment

---
 packages/utils/src/object.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/utils/src/object.ts b/packages/utils/src/object.ts
index e9373797c44f..5957214ecc86 100644
--- a/packages/utils/src/object.ts
+++ b/packages/utils/src/object.ts
@@ -206,6 +206,8 @@ export function extractExceptionKeysForMessage(exception: Record<string, unknown
 /**
  * Given any object, return the new object with removed keys that value was `undefined`.
  * Works recursively on objects and arrays.
+ *
+ * Attention: This function keeps circular references in the returned object.
  */
 export function dropUndefinedKeys<T>(val: T): T {
   // This function just proxies `_dropUndefinedKeys` to keep the `memoBuilder` out of this function's API