fix: handle circular references correctly in objects (closes jestjs#8663

)
lucasfcosta · Jul 13, 2019 · e087fc6 · e087fc6
1 parent b76f01b
commit e087fc6
Show file tree

Hide file tree

Showing 3 changed files with 101 additions and 11 deletions.
diff --git a/packages/expect/src/__tests__/__snapshots__/matchers.test.js.snap b/packages/expect/src/__tests__/__snapshots__/matchers.test.js.snap
@@ -4092,6 +4092,30 @@ Expected: not <green>Set {2, 1}</>
 Received:     <red>Set {1, 2}</>"
 `;
 
+exports[`toMatchObject() circular references simple circular references 1`] = `
+"<dim>expect(</><red>received</><dim>).</>not<dim>.</>toMatchObject<dim>(</><green>expected</><dim>)</>
+
+Expected: not <green>{\\"ref\\": [Circular]}</>"
+`;
+
+exports[`toMatchObject() circular references simple circular references 2`] = `
+"<dim>expect(</><red>received</><dim>).</>not<dim>.</>toMatchObject<dim>(</><green>expected</><dim>)</>
+
+Expected: not <green>[[Circular]]</>"
+`;
+
+exports[`toMatchObject() circular references transitive circular references 1`] = `
+"<dim>expect(</><red>received</><dim>).</>not<dim>.</>toMatchObject<dim>(</><green>expected</><dim>)</>
+
+Expected: not <green>{\\"nestedObj\\": {\\"parentObj\\": [Circular]}}</>"
+`;
+
+exports[`toMatchObject() circular references transitive circular references 2`] = `
+"<dim>expect(</><red>received</><dim>).</>not<dim>.</>toMatchObject<dim>(</><green>expected</><dim>)</>
+
+Expected: not <green>[[[Circular]]]</>"
+`;
+
 exports[`toMatchObject() throws expect("44").toMatchObject({}) 1`] = `
 "<dim>expect(</><red>received</><dim>).</>toMatchObject<dim>(</><green>expected</><dim>)</>
 

diff --git a/packages/expect/src/__tests__/matchers.test.js b/packages/expect/src/__tests__/matchers.test.js
@@ -1537,6 +1537,49 @@ describe('toMatchObject()', () => {
     }
   }
 
+  describe('circular references', () => {
+    test('simple circular references', () => {
+      const circularObj = {};
+      circularObj.ref = circularObj;
+
+      jestExpect(circularObj).toMatchObject(circularObj);
+      expect(() => {
+        jestExpect(circularObj).not.toMatchObject(circularObj);
+      }).toThrowErrorMatchingSnapshot();
+
+      const circularArray = [];
+      circularArray.push(circularArray);
+      jestExpect(circularArray).toMatchObject(circularArray);
+      expect(() => {
+        jestExpect(circularArray).not.toMatchObject(circularArray);
+      }).toThrowErrorMatchingSnapshot();
+    });
+
+    test('transitive circular references', () => {
+      const transitiveCircularObj = {};
+      transitiveCircularObj.nestedObj = {parentObj: transitiveCircularObj};
+
+      jestExpect(transitiveCircularObj).toMatchObject(transitiveCircularObj);
+      expect(() => {
+        jestExpect(transitiveCircularObj).not.toMatchObject(
+          transitiveCircularObj,
+        );
+      }).toThrowErrorMatchingSnapshot();
+
+      const transitiveCircularArray = [];
+      const refArray = [transitiveCircularArray];
+      transitiveCircularArray.push(refArray);
+      jestExpect(transitiveCircularArray).toMatchObject(
+        transitiveCircularArray,
+      );
+      expect(() => {
+        jestExpect(transitiveCircularArray).not.toMatchObject(
+          transitiveCircularArray,
+        );
+      }).toThrowErrorMatchingSnapshot();
+    });
+  });
+
   [
     [{a: 'b', c: 'd'}, {a: 'b'}],
     [{a: 'b', c: 'd'}, {a: 'b', c: 'd'}],

diff --git a/packages/expect/src/utils.ts b/packages/expect/src/utils.ts
@@ -257,9 +257,10 @@ export const iterableEquality = (
   return true;
 };
 
+const isObject = (a: any) => a !== null && typeof a === 'object';
+
 const isObjectWithKeys = (a: any) =>
-  a !== null &&
-  typeof a === 'object' &&
+  isObject(a) &&
   !(a instanceof Error) &&
   !(a instanceof Array) &&
   !(a instanceof Date);
@@ -268,16 +269,38 @@ export const subsetEquality = (
   object: any,
   subset: any,
 ): undefined | boolean => {
-  if (!isObjectWithKeys(subset)) {
-    return undefined;
-  }
+  const seenReferences = new WeakMap();
+
+  // subsetEquality needs to keep track of the references
+  // it has already visited to avoid infinite loops in case
+  // there are circular references in the subset passed to it.
+  const subsetEqualityWithContext = (
+    seenReferences: WeakMap<object, boolean>,
+  ) => (object: any, subset: any): undefined | boolean => {
+    if (!isObjectWithKeys(subset)) {
+      return undefined;
+    }
 
-  return Object.keys(subset).every(
-    key =>
-      object != null &&
-      hasOwnProperty(object, key) &&
-      equals(object[key], subset[key], [iterableEquality, subsetEquality]),
-  );
+    return Object.keys(subset).every(key => {
+      const target = subset[key];
+      if (isObject(target)) {
+        console.log(typeof target, target);
+        if (seenReferences.get(target)) return true;
+        seenReferences.set(target, true);
+      }
+
+      return (
+        object != null &&
+        hasOwnProperty(object, key) &&
+        equals(object[key], target, [
+          iterableEquality,
+          subsetEqualityWithContext(seenReferences),
+        ])
+      );
+    });
+  };
+
+  return subsetEqualityWithContext(seenReferences)(object, subset);
 };
 
 export const typeEquality = (a: any, b: any) => {