refactor: separate out PanicHandlerPlugin

[simbleau]

Objective

• Allow configuring of platform-specific panic handlers.
• Remove the silent overwrite of the WASM panic handler
• Closes LogPlugin silently overwrites the panic hook in WASM #12546

Solution

• Separates the panic handler to a new plugin, PanicHandlerPlugin.
• PanicHandlerPlugin was added to DefaultPlugins.
• Can be disabled on DefaultPlugins, in the case someone needs to configure custom panic handlers.

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Changelog

Added

• A PanicHandlerPlugin was added to the DefaultPlugins, which now sets sensible target-specific panic handlers.

Changed

• On WASM, the panic stack trace was output to the console through the BevyLogPlugin. Since this was separated out into PanicHandlerPlugin, you may need to add the new PanicHandlerPlugin (included in DefaultPlugins).

Migration Guide

• If you used MinimalPlugins with LogPlugin for a WASM-target build, you will need to add the new PanicHandlerPlugin to set the panic behavior to output to the console. Otherwise, you will see the default panic handler (opaque, unreachable errors in the console).

[alice-i-cecile]

We should be able to remove the dependency on console_error_panic_hook from bevy_log now, right?

[alice-i-cecile]

I think this basically makes sense as a separate crate, although it's a bit weird to have something that small. What about as part of bevy_app instead? I think that will reduce complexity and controversy here by quite a bit.

[simbleau]

I think this basically makes sense as a separate crate, although it's a bit weird to have something that small. What about as part of bevy_app instead? I think that will reduce complexity and controversy here by quite a bit.

I am fine to go that way, but I am hoping in the future this could evolve to be configurable, e.g.

struct PanicHandlerPlugin {
    handler: Box<dyn Fn(&PanicInfo)>
}

For now I think this makes sense as a very simple separation that can satisfy and close #12546 , with more sensible configuration to Android and other targets in the future.

I'm also a little confused how you imagine this fitting into bevy_app - can you expand?

We should be able to remove the dependency on console_error_panic_hook from bevy_log now, right?

Correct, I just removed it.

[alice-i-cecile]

I'm also a little confused how you imagine this fitting into bevy_app - can you expand?

I was just thinking drop the module in there directly; no changes beyond copy-paste. This is fine though: don't worry about changing it. More config would be great in the future.

[JMS55]

I think we need to update the docs for default plugins right.

[simbleau]

I think we need to update the docs for default plugins right.

Fixed! Good catch.