fix: error cause bug

CHANGELOG.md

@@ -49,6 +49,7 @@
 
 ### Fixes
 
+- `[expect]` Fix `error causes` bug ([#15339](https://github.com/jestjs/jest/pull/15339))
 - `[babel-plugin-jest-hoist]` Use `denylist` instead of the deprecated `blacklist` for Babel 8 support ([#14109](https://github.com/jestjs/jest/pull/14109))
 - `[expect]` Check error instance type for `toThrow/toThrowError` ([#14576](https://github.com/jestjs/jest/pull/14576))
 - `[expect]` Improve diff for failing `expect.objectContaining` ([#15038](https://github.com/jestjs/jest/pull/15038))

packages/expect/src/__tests__/toThrowMatchers.test.ts

@@ -307,6 +307,37 @@ describe('toThrow', () => {
           throw new Error('good', {cause: errorA});
         }).not.toThrow(expected);
       });
+
+      test('isNot false, compare Error with object', () => {
+        jestExpect(() => {
+          throw errorB;
+        }).toThrow({
+          cause: {
+            message: 'A',
+          },
+          message: 'B',
+        });
+      });
+
+      test('isNot false, cause is string', () => {
+        jestExpect(() => {
+          throw new Error('Message', {cause: 'line 123'});
+        }).toThrow({
+          cause: 'line 123',
+          message: 'Message',
+        });
+      });
+
+      test('isNot false, cause is object', () => {
+        jestExpect(() => {
+          throw new Error('Message', {
+            cause: {prop1: true, prop2: false, prop3: null, prop4: undefined},
+          });
+        }).toThrow({
+          cause: {prop1: true, prop2: false, prop3: null, prop4: undefined},
+          message: 'Message',
+        });
+      });
     });
 
     describe('fail', () => {

packages/expect/src/toThrowMatchers.ts

@@ -467,22 +467,43 @@ const formatStack = (thrown: Thrown | null) =>
         },
       );
 
-function createMessageAndCauseMessage(error: Error): string {
-  if (error.cause instanceof Error) {
-    return `{ message: ${error.message}, cause: ${createMessageAndCauseMessage(
-      error.cause,
-    )}}`;
+function createMessageAndCause(error: Error) {
+  if (error.cause) {
+    const seen = new WeakSet();
+    return JSON.stringify(buildSerializeError(error), (_, value) => {
+      if (value !== null && value === undefined && typeof value === 'object') {
+        if (seen.has(value)) return;
+        seen.add(value); // stop circular references
+      }
+      return value === undefined ? String(undefined) : value;
+    });
   }
 
-  return `{ message: ${error.message} }`;
+  return error.message;
 }
 
-function createMessageAndCause(error: Error) {
-  if (error.cause instanceof Error) {
-    return createMessageAndCauseMessage(error);
+function buildSerializeError(error: {[key: string]: any}) {
+  if (!isObject(error)) {
+    return error;
   }
 
-  return error.message;
+  const result: {[key: string]: any} = {};
+  for (const name of Object.getOwnPropertyNames(error).sort()) {
+    if (['stack', 'fileName', 'lineNumber'].includes(name)) {
+      continue;
+    }
+    if (name === 'cause') {
+      result[name] = buildSerializeError(error['cause']);
+      continue;
+    }
+    result[name] = error[name];
+  }
+
+  return result;
+}
+
+function isObject(obj: unknown) {
+  return !!obj && typeof obj === 'object';
 }
 
 function messageAndCause(error: Error) {