fix trackProperties recursion

[paztis]

passdown the checkedObjects to detect circularity

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[soyjuanmacias]

Same problem here, which can be solved with this PR

[markerikson]

The stack trace here is particularly odd, given that line 138 seems to be in the middle of a comment?

TypeError: Cannot read properties of undefined (reading 'value')
 ❯ detectMutations node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:138:40
 ❯ detectMutations node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:138:20
 ❯ detectMutations node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:138:20
 ❯ detectMutations node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:138:20
 ❯ Object.detectMutations node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:41:3
 ❯ node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:187:5
 ❯ Object.measureTime node_modules/@reduxjs/toolkit/src/utils.ts:31:12
 ❯ node_modules/@reduxjs/toolkit/src/immutableStateInvariantMiddleware.ts:185:16
 ❯ src/tests/immutableStateInvariantMiddleware.test.ts:148:7

redux-toolkit/packages/toolkit/src/immutableStateInvariantMiddleware.ts

Lines 134 to 150 in 6a17ea9

	export interface ImmutableStateInvariantMiddlewareOptions {
	/**
	Callback function to check if a value is considered to be immutable.
	This function is applied recursively to every value contained in the state.
	The default implementation will return true for primitive types
	(like numbers, strings, booleans, null and undefined).
	*/
	isImmutable?: IsImmutableFunc
	/**
	An array of dot-separated path strings that match named nodes from
	the root state to ignore when checking for immutability.
	Defaults to undefined
	*/
	ignoredPaths?: IgnorePaths
	/** Print a warning if checks take longer than N ms. Default: 32ms */
	warnAfter?: number
	}

[markerikson]

I can reproduce the brokenness from this change locally, although the line numbers are different:

TypeError: Cannot read properties of undefined (reading 'value')
 ❯ detectMutations src/immutableStateInvariantMiddleware.ts:117:23
    115|       isImmutable,
    116|       ignoredPaths,
    117|       trackedProperty.children[key],
       |                       ^
    118|       obj[key],
    119|       sameRef,
 ❯ detectMutations src/immutableStateInvariantMiddleware.ts:114:20
 ❯ detectMutations src/immutableStateInvariantMiddleware.ts:114:20
 ❯ detectMutations src/immutableStateInvariantMiddleware.ts:114:20
 ❯ Object.detectMutations src/immutableStateInvariantMiddleware.ts:24:14
 ❯ src/immutableStateInvariantMiddleware.ts:228:28
 ❯ Object.measureTime src/utils.ts:9:16
 ❯ src/immutableStateInvariantMiddleware.ts:225:22
 ❯ src/tests/immutableStateInvariantMiddleware.test.ts:148:7

[markerikson]

It looks like the ".value of undefined" bit is related to the mock data being generated for the test:

state.foo.bar = new Array(10).fill({ value: 'more' })

rather than the .value field from the TrackedProperty objects.

Honestly I'm not sure what's going on here, and this is low enough priority that I don't want to get bogged down debugging it atm.

[soyjuanmacias]

Just solve it @paztis. Can you try it and modify #4844 ?

Problem:

I was encountering false-positive mutation detections because my trackProperties function wasn't consistently memoizing object references. When the same object was encountered multiple times (for example, using Array.fill({ value: 'more' }) or updating isPrefetch), a new tracker with an empty children property was created instead of reusing the existing one. This inconsistency caused the mutation detector to incorrectly report changes.

Solution:

I fixed the issue by introducing memoization in trackProperties using a WeakMap. Now, when processing an object:

• If the object is a primitive or already considered immutable, I simply return a basic tracker.
• If I’ve already seen the object, I retrieve its tracker from the WeakMap to ensure consistency.
• Otherwise, I create a new tracker, store it in the WeakMap, and use it for all future detections.

This change ensures that each object reference is tracked only once, completely eliminating the false-positive mutation detections.

This is the complete code for trackProperties with the problem fixed. @paztis , only have replace and update the PR.

function trackProperties(
  isImmutable: IsImmutableFunc,
  ignorePaths: IgnorePaths = [],
  obj: Record<string, any>,
  path: string = '',
  checkedObjects: WeakMap<any, TrackedProperty> = new WeakMap(),
) {
  if (typeof obj !== 'object' || obj === null || isImmutable(obj)) {
    return { value: obj, children: {} }
  }

  if (checkedObjects.has(obj)) {
    return checkedObjects.get(obj)!
  }

  const tracked: TrackedProperty = { value: obj, children: {} }
  checkedObjects.set(obj, tracked)

  for (const key in obj) {
    const childPath = path ? path + '.' + key : key
    if (ignorePaths.length && ignorePaths.indexOf(childPath) !== -1) {
      continue
      }

    tracked.children[key] = trackProperties(
      isImmutable,
      ignorePaths,
      obj[key],
      childPath,
      checkedObjects,
    )
  }
  return tracked as TrackedProperty
}

And here, tests passed locally: