React Example Node Leak

[samccone]

Steps to reproduce

• start timeline profiler
  • add three todos
  • delete three todos
  • (repeat above 2 more times)
• force GC
• stop timeline profiler

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It seems like one event listener is not getting unbound, this seems like a leak. ⛲

[samccone]

ping @petehunt @chenglou

[chenglou]

Event listener? Afaik there are only react event listeners in there and they're all released correctly. Maybe it's something else?

[samccone]

Hi @chenglou thanks for getting back.

One thing that seems suspicious to me is the fact that once I started my test steps an event listener was bound and then never released even after a forced GC. Is this expected?

[samccone]

After a new round of profiling @chenglou and warming the initial render state (adding and removing one todo) before starting my tests I am confident that there is a leak in this example.

Note how the heap size increases and I have a whole bunch of new ReactElements between each test:

Also each time I go through the steps of my test I end up with more nodes each run:

Based on this information I am quite confident there is a leak in this example (unless there is some caching behavior that can be accounted for)

Let me know if I can be of any more help

[sophiebits]

If you add some todos and remove them before taking the first snapshot, you shouldn't see the listener. This is because React adds a single top-level listener for each event used and some events are not used except by the <TodoItem /> component. I can't repro the HTML elements you're seeing. I get this:

The new ReactElements in the heap snapshot are there because each time you call render, new elements are allocated – but the old ones that they replace are freed, so there shouldn't be a real leak.

[samccone]

Hey @spicyj thanks for getting back to me, I agree there is no listener leak that was a mistake on my part. As far as the ReactElement issue, I have codified the process here #1368

and am still seeing a growth over time (even with a forced GC), let me know if this expected or if I have missed something. Thanks again for your time!

[flashdesignory]

Closing since React was updated #2202