Fragment induced memory leak if not keyed and state change triggered by context

[glenveegee]

• [ X ] Check if updating to the latest Preact version resolves the issue It does not resolve the issue

Describe the bug When a parent component undergoes state transitions due to context changes, and it returns a fragment which bounds two or more child components that are themselves modified by changes in different parts of the context (so keying the fragment makes no sense), memory will leak and the heap will ultimately fill up and throw an error

To Reproduce

Instructions on how to reproduce and a demonstration of the memory leak are available in the following repo: https://github.com/glenveegee/preact_fragment_memleak

Steps to reproduce the behaviour:

• Install the node dependencies after downloading the repo
• Starts the dev server (hosted at http://localhost:5173/)
• Open the developer console to use the memory profiling tools
• Profile memory to obtain a non-leaky memory profile
• Visit http://localhost:5173/leaky and perform the memory profiling again
• Compare and contrast memory profiles

Expected behavior

• Manual garbage collection should return heap memory to "normal" levels.
• Profiling heap memory without manual garbage collection should show automatic, periodic garbage collection back to "normal" levels

[glenveegee]

I should add that running the same code with React has no such memory leak issue with Fragment used in the way it is in the demo repo above (https://github.com/glenveegee/preact_fragment_memleak)

[JoviDeCroock]

@glenveegee this is probably only present in development and is an issue with prefresh https://github.com/preactjs/prefresh/issues/558 - you can try to disable prefresh in vite to reproduce that