Undo changes to dropUndefinedKeys

Author: Luca Forstner

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';
 
 /**
@@ -203,61 +204,42 @@ export function extractExceptionKeysForMessage(exception: Record<string, unknown
 }
 
 /**
- * Given any object, return a new object having removed all fields whose value was `undefined`.
+ * 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>(inputValue: T): T {
-  // This map keeps track of what already visited nodes map to.
-  // Our Set - based memoBuilder doesn't work here because we want to the output object to have the same circular
-  // references as the input object.
-  const memoizationMap = new Map<unknown, unknown>();
-
+export function dropUndefinedKeys<T>(val: T): T {
   // This function just proxies `_dropUndefinedKeys` to keep the `memoBuilder` out of this function's API
-  return _dropUndefinedKeys(inputValue, memoizationMap);
+  return _dropUndefinedKeys(val, memoBuilder());
 }
 
-function _dropUndefinedKeys<T>(inputValue: T, memoizationMap: Map<unknown, unknown>): T {
-  if (isPlainObject(inputValue)) {
-    // If this node has already been visited due to a circular reference, return the object it was mapped to in the new object
-    const memoVal = memoizationMap.get(inputValue);
-    if (memoVal !== undefined) {
-      return memoVal as T;
-    }
-
-    const returnValue: { [key: string]: any } = {};
-    // Store the mapping of this value in case we visit it again, in case of circular data
-    memoizationMap.set(inputValue, returnValue);
+function _dropUndefinedKeys<T>(val: T, memo: MemoFunc): T {
+  const [memoize] = memo; // we don't need unmemoize because we don't need to visit nodes twice
 
-    for (const key of Object.keys(inputValue)) {
-      if (typeof inputValue[key] !== 'undefined') {
-        returnValue[key] = _dropUndefinedKeys(inputValue[key], memoizationMap);
+  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], memo);
       }
     }
-
-    return returnValue as T;
+    return rv as T;
   }
 
-  if (Array.isArray(inputValue)) {
-    // If this node has already been visited due to a circular reference, return the array it was mapped to in the new object
-    const memoVal = memoizationMap.get(inputValue);
-    if (memoVal !== undefined) {
-      return memoVal as T;
+  if (Array.isArray(val)) {
+    if (memoize(val)) {
+      return val;
     }
-
-    const returnValue: unknown[] = [];
-    // Store the mapping of this value in case we visit it again, in case of circular data
-    memoizationMap.set(inputValue, returnValue);
-
-    inputValue.forEach((item: unknown) => {
-      returnValue.push(_dropUndefinedKeys(item, memoizationMap));
-    });
-
-    return returnValue as unknown as T;
+    return (val as any[]).map(item => {
+      return _dropUndefinedKeys(item, memo);
+    }) as any;
   }
 
-  return inputValue;
+  return val;
 }
 
 /**

packages/utils/test/object.test.ts

@@ -200,34 +200,28 @@ describe('dropUndefinedKeys()', () => {
     });
   });
 
-  test('should not throw on objects with circular reference', () => {
-    const chicken: any = {
+  test('objects with circular reference', () => {
+    const dog: any = {
       food: undefined,
     };
 
-    const egg = {
-      edges: undefined,
-      contains: chicken,
+    const human = {
+      brain: undefined,
+      pets: dog,
     };
 
-    chicken.lays = egg;
-
-    const droppedChicken = dropUndefinedKeys(chicken);
-
-    // Removes undefined keys
-    expect(Object.keys(droppedChicken)).toEqual(['lays']);
-    expect(Object.keys(droppedChicken.lays)).toEqual(['contains']);
-
-    // Returns new object
-    expect(chicken === droppedChicken).toBe(false);
-    expect(chicken.lays === droppedChicken.lays).toBe(false);
+    const rat = {
+      scares: human,
+      weight: '4kg',
+    };
 
-    // Returns new references within objects
-    expect(chicken === droppedChicken.lays.contains).toBe(false);
-    expect(egg === droppedChicken.lays.contains.lays).toBe(false);
+    dog.chases = rat;
 
-    // Keeps circular reference
-    expect(droppedChicken.lays.contains === droppedChicken).toBe(true);
+    expect(dropUndefinedKeys(human)).toStrictEqual({
+      pets: {
+        chases: rat,
+      },
+    });
   });
 
   test('arrays with circular reference', () => {