Invalid runtime error: tracked property has "already been used previously in the same computation"

[ChrisN-transnexus]

🐞 Describe the Bug

You attempted to update currPosition on MyComponent, but it had already been used previously in the same computation. The tracked property name and component name are irrelevant. This occurs in an Ember 6 app after update from 5.12, and in an Ember 6 V2 addon being run in the test-app after update from 5.12.

🔬 Minimal Reproduction

This code worked 100% fine in Ember 5.12. Then the project (addon and/or app) was updated to Ember 6.0, which caused this error to be generated. I'm not going to create a reproduction, the codebase is private and I don't have time to do so. This error ONLY occurs when updating from Ember 5.12 to 6.0. If the code worked in Ember 5.12, it should also work in Ember 6.0 as no features, deprecations, etc, were supposed to have changed between these versions.

😕 Actual Behavior

While developing an app and an addon, the error "You attempted to update currPosition on MyComponent, but it had already been used previously in the same computation." occurs. The app's execution is halted.

🤔 Expected Behavior

There should not be an error, the code has not changed, only the Ember dependency.

🌍 Environment

• Ember: - 6.0.1
• Ember-CLI: - 6.0.1
• Node.js/npm: - 22
• OS: - MacOS
• Browser: - Chrome

[NullVoxPopuli]

Hey, sorry you're having trouble.

You mention "ember 5.12" -- but are you talking ember-cli or ember-source? both? the clarity is needed. tyty!

Here is the diff: v5.12.0...v6.0.1-ember-source

• we didn't make any changes to the renderer
• we did update the private glimmer packages from glimmer-vm from 0.92 to 0.92.4
  • here is that diff: glimmerjs/glimmer-vm@v0.92.0...v0.92.4-@glimmer/manager
  • here is the changelog entry:
    • 0.92.1: https://github.com/glimmerjs/glimmer-vm/blob/main/CHANGELOG.md#release-2024-09-11
    • 0.92.2: https://github.com/glimmerjs/glimmer-vm/blob/main/CHANGELOG.md#release-2024-09-12-1
    • https://github.com/glimmerjs/glimmer-vm/blob/main/CHANGELOG.md#release-2024-09-12
      These were all due to some release troubles the package was having -- which should be evident by the diff linked above between the two versions
  • The key thing is that this change removed code that should not be shipped to production (debug code)
    • this code was already present in prior versions, but post 0.92.4, participates in dead code elimination and has no other behaviors.

I agree that you should not have have had an issue with back-tracking re-render.

The key change you should have encountered is moving from ember-source 5.5 and then again in 5.11 (iirc) -- these were more significant glimmer-vm package upgrades -- but since you say you're already on ember 5.12 -- I guess you already got passed those.

During 5.5 and 5.11, we released some bugfixes, which a number of folks had issues with the backtracking re-renderer assertion.

This was considered a bugfix, because your app typicall (afaik) just didn't work or infinitely looped without you noticing.

Without a reproduction I can't help you further <3
Happy to discuss / look at repro tho

[kategengler]

Please provide code examples, if not a full reproduction. Without that, and without other reports, there is no way for us to determine what may have changed.

[kategengler]

Additionally, please try 6.4 or 6.8 of ember-source -- they are the currently supported LTSes.

[Jopie01]

Please take a look at these answers:

• [Bug] Regression in 5.6.0 concerning auto-tracking #20657 (comment)
• Incorrect(?) rerender assertion with auto-tracking of modifiers glimmerjs/glimmer-vm#1762 (comment)

Read the rest of the issues also carefully.