Fix(expect-utils): Circular references not being caught when inside arrays

CHANGELOG.md

@@ -43,6 +43,7 @@
 - `[@jest/expect-utils]` [**BREAKING**] exclude non-enumerable in object matching ([#14670](https://github.com/jestjs/jest/pull/14670))
 - `[@jest/expect-utils]` Fix comparison of `URL` ([#14672](https://github.com/jestjs/jest/pull/14672))
 - `[@jest/expect-utils]` Check `Symbol` properties in equality ([#14688](https://github.com/jestjs/jest/pull/14688))
+- `[@jest/expect-utils]` Catch circular references within arrays when matching objects ([#14894](https://github.com/jestjs/jest/pull/14894))
 - `[jest-leak-detector]` Make leak-detector more aggressive when running GC ([#14526](https://github.com/jestjs/jest/pull/14526))
 - `[jest-runtime]` Properly handle re-exported native modules in ESM via CJS ([#14589](https://github.com/jestjs/jest/pull/14589))
 - `[jest-util]` Make sure `isInteractive` works in a browser ([#14552](https://github.com/jestjs/jest/pull/14552))

e2e/__tests__/circularRefInBuiltInObj.test.ts

@@ -0,0 +1,89 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+describe('matches circular references nested in:', () => {
+  interface CircularObj {
+    ref: unknown;
+    [prop: string]: unknown;
+  }
+
+  test('arrays', () => {
+    type CircularArray = CircularObj & {ref: Array<unknown>};
+
+    const a: CircularArray = {c: 1, ref: [1]};
+    const b: CircularArray = {c: 1, ref: [1]};
+
+    a.ref.push(a);
+    b.ref.push(b);
+    expect(a).toMatchObject(b);
+
+    b.ref = [];
+    expect(a).not.toMatchObject(b);
+
+    b.ref = [1];
+    expect(a).not.toMatchObject(b);
+  });
+
+  test('deeply nested array properties', () => {
+    type DeepCircularArray = CircularObj & {ref: {inner: Array<unknown>}};
+    const a: DeepCircularArray = {
+      c: 1,
+      ref: {
+        inner: [1],
+      },
+    };
+    const b: DeepCircularArray = {
+      c: 1,
+      ref: {
+        inner: [1],
+      },
+    };
+    a.ref.inner.push(a);
+    b.ref.inner.push(b);
+    expect(a).toMatchObject(b);
+
+    b.ref.inner = [];
+    expect(a).not.toMatchObject(b);
+
+    b.ref.inner = [1];
+    expect(a).not.toMatchObject(b);
+  });
+
+  test('sets', () => {
+    type CircularSet = CircularObj & {ref: Set<unknown>};
+
+    const a: CircularSet = {c: 1, ref: new Set()};
+    const b: CircularSet = {c: 1, ref: new Set()};
+
+    a.ref.add(a);
+    b.ref.add(b);
+    expect(a).toMatchObject(b);
+
+    b.ref.clear();
+    expect(a).not.toMatchObject(b);
+
+    b.ref.add(1);
+    expect(a).not.toMatchObject(b);
+  });
+
+  test('maps', () => {
+    type CircularMap = CircularObj & {ref: Map<string, unknown>};
+
+    const a: CircularMap = {c: 1, ref: new Map()};
+    const b: CircularMap = {c: 1, ref: new Map()};
+
+    a.ref.set('innerRef', a);
+    b.ref.set('innerRef', b);
+    expect(a).toMatchObject(b);
+
+    b.ref.clear();
+    expect(a).not.toMatchObject(b);
+
+    b.ref.set('innerRef', 1);
+    expect(a).not.toMatchObject(b);
+  });
+});

packages/expect-utils/src/utils.ts

@@ -355,12 +355,14 @@ export const subsetEquality = (
         return undefined;
       }
 
-      return getObjectKeys(subset).every(key => {
+      if (seenReferences.has(subset)) return undefined;
+      seenReferences.set(subset, true);
+
+      const matchResult = getObjectKeys(subset).every(key => {
         if (isObjectWithKeys(subset[key])) {
           if (seenReferences.has(subset[key])) {
             return equals(object[key], subset[key], filteredCustomTesters);
           }
-          seenReferences.set(subset[key], true);
         }
         const result =
           object != null &&
@@ -377,6 +379,8 @@ export const subsetEquality = (
         seenReferences.delete(subset[key]);
         return result;
       });
+      seenReferences.delete(subset);
+      return matchResult;
     };
 
   return subsetEqualityWithContext()(object, subset);