fix: circular refs

Author: Thanga-Ganapathy

.changeset/early-hats-thank.md

@@ -0,0 +1,5 @@
+---
+"@opentf/obj-diff": minor
+---
+
+Fixed circular refs.

packages/obj-diff/__tests__/diff.test.ts

@@ -1,3 +1,4 @@
+import { clone } from "@opentf/std";
 import { diff } from "../src";
 
 describe("diff", () => {
@@ -285,13 +286,48 @@ describe("diff", () => {
   });
 
   test("circular refs", () => {
-    let obj1 = {};
-    obj1.a = obj1;
-    expect(diff(obj1, obj1)).toEqual([]);
+    let obj1 = {
+      a: 1,
+    };
+    obj1.self = obj1;
+    let obj2 = structuredClone(obj1);
+    expect(diff(obj1, obj2)).toEqual([]);
+
+    obj1 = {
+      a: 1,
+    };
+    obj1.self = obj1;
+    obj2 = structuredClone(obj1);
+    obj2.self = null;
+    expect(diff(obj1, obj2)).toEqual([
+      {
+        p: ["self"],
+        t: 2,
+        v: null,
+      },
+    ]);
+
+    const tmp = { a: 1 };
+    obj1 = { a: { tmp }, b: { tmp } };
+    obj2 = structuredClone(obj1);
+    obj2.a.tmp.b = 2;
+
+    expect(diff(obj1, obj2)).toEqual([
+      {
+        p: ["a", "tmp", "b"],
+        t: 1,
+        v: 2,
+      },
+      {
+        p: ["b", "tmp", "b"],
+        t: 1,
+        v: 2,
+      },
+    ]);
 
     obj1 = { a: { b: 2, c: [1, 2, 3] } };
     obj1.b = obj1;
-    const obj2 = { a: { b: 2, c: [1, 5, 3] } };
+    obj2 = { a: { b: 2, c: [1, 5, 3] } };
     obj2.b = obj2;
     expect(diff(obj1, obj2)).toEqual([
       {
@@ -399,4 +435,23 @@ describe("diff", () => {
 
     expect(diff(a, b)).toEqual([{ t: 2, p: ["m"], v: new Set([1]) }]);
   });
+
+  test("multiple references to the same object", () => {
+    const array = [1];
+    const a = { test1: array, test2: array };
+    const b = clone(a);
+    b.test1.push(2);
+    expect(diff(a, b)).toEqual([
+      {
+        p: ["test1", 1],
+        t: 1,
+        v: 2,
+      },
+      {
+        p: ["test2", 1],
+        t: 1,
+        v: 2,
+      },
+    ]);
+  });
 });

packages/obj-diff/jsr.json

@@ -1,6 +1,6 @@
 {
   "name": "@opentf/obj-diff",
-  "version": "0.9.0",
+  "version": "0.10.0",
   "exports": "./src/index.ts",
   "imports": {
     "@opentf/std": "jsr:@opentf/[email protected]"

packages/obj-diff/src/diff.ts

@@ -5,8 +5,7 @@ function objDiff(
   a: object,
   b: object,
   path: Array<string | number>,
-  objRefSet1: WeakSet<WeakKey>,
-  objRefSet2: WeakSet<WeakKey>
+  _refs: WeakSet<WeakKey>
 ): DiffResult[] {
   const result: DiffResult[] = [];
 
@@ -17,12 +16,12 @@ function objDiff(
     b !== null
   ) {
     // For circular refs
-    if (objRefSet1.has(a) && objRefSet2.has(b)) {
+    if (_refs.has(a) && _refs.has(b)) {
       return [];
     }
 
-    objRefSet1.add(a as WeakKey);
-    objRefSet2.add(b as WeakKey);
+    _refs.add(a as WeakKey);
+    _refs.add(b as WeakKey);
 
     if (Array.isArray(a) && Array.isArray(b)) {
       for (let i = 0; i < a.length; i++) {
@@ -32,8 +31,7 @@ function objDiff(
               a[i],
               (b as Array<unknown>)[i] as object,
               [...path, i],
-              objRefSet1,
-              objRefSet2
+              _refs
             )
           );
         } else {
@@ -51,6 +49,9 @@ function objDiff(
         }
       }
 
+      _refs.delete(a);
+      _refs.delete(b);
+
       return result;
     }
 
@@ -65,8 +66,7 @@ function objDiff(
               (a as Record<string, unknown>)[k] as object,
               (b as Record<string, unknown>)[k] as object,
               [...path, k],
-              objRefSet1,
-              objRefSet2
+              _refs
             )
           );
         } else {
@@ -84,6 +84,9 @@ function objDiff(
         }
       }
 
+      _refs.delete(a);
+      _refs.delete(b);
+
       return result;
     }
 
@@ -138,8 +141,5 @@ function objDiff(
  * diff({a: 1}, {a: 5}) //=> [{t: 2, p: ['a'], v: 5}]
  */
 export default function diff(obj1: object, obj2: object): Array<DiffResult> {
-  const objRefSet1 = new WeakSet();
-  const objRefSet2 = new WeakSet();
-
-  return objDiff(obj1, obj2, [], objRefSet1, objRefSet2);
+  return objDiff(obj1, obj2, [], new WeakSet());
 }