Show errors from non-main threads in editor

[derammo]

The GDScript VM breaks out of the current function on error, such as assertion failures or general script errors. These errors cause debug breakpoints when running under the debugger/editor. However, threads that are not the main thread are not able to be debugged. For any worker threads, these errors were just printed to stderr, and then the thread would silently exit the current frame, leading to unpredictable results. There was no indication in the Editor itself.

This change submits such errors to the error reporting facility of the debugger also, so they can be displayed in the editor as Errors. They still don't cause debug breakpoints, because that would require general support for thread debugging. This is for notifications only.

Example program:

extends Node

var typed: int 

func _ready():
	var thread = Thread.new()
	thread.start(_thread_function)
	thread.wait_to_finish()
	
func _thread_function():
	assert(typed > 0, "this was only shown on stderr before, with no indication in the Editor")

[akien-mga]

Does this solve #2446 ?

Edit: I commented before reading the PR, it does not:

They still don't cause debug breakpoints, because that would require general support for thread debugging. This is for notifications only.

[derammo]

@akien-mga this PR is me learning the code base around VM and debugger enough to go work on 2446...

[derammo]

@Faless can I close this? You mentioned elsewhere that you thought it was wrong, but that may have been a misunderstanding.

[adamscott]

CC @Faless @vnen Is it mergeable/safe enough for 4.1? If not, I'll push the milestone to 4.2.

[akien-mga]

CC @Faless @vnen Is it mergeable/safe enough for 4.1? If not, I'll push the milestone to 4.2.

This may be superseded by #76582 which is planned for 4.2. Once that one is merged, this one should be re-evaluated to see if it's still relevant (partially or in full).

[AThousandShips]

Seeing how #76582 is merged, is this still relevant?

[akien-mga]

The reproduction case from the OP is indeed well supported in 4.2-beta:

So this doesn't seem needed anymore. Thanks for the contribution!