UNUSED_SIGNAL warning if signal is only used via emit_signal()

[lostminds]

Tested versions

v4.3.dev5
not reproducable in v4.3.dev4

System information

macOS 14.4

Issue description

If you emit signals using emit_signal("signal_name") this will no longer register in 4.3dev5 as using this signal and trigger an UNUSED_SIGNAL warning for the signal.

Steps to reproduce

Write a simple script like

extends Node

signal value_changed()

var value:bool = false:
	set(new_value):
		if (new_value != value):
			value = new_value
			emit_signal("value_changed")

And observer the warning:
Line 3 (UNUSED_SIGNAL):The signal "value_changed" is declared but never explicitly used in the class.

If you instead use value_changed.emit() the warning is not shown.

If the script is used in the project you'll get a similar warning in the debug output running the game.

Minimal reproduction project (MRP)

See script lines above.

[AThousandShips]

Thank you for your report, consolidating in:

• Erroneous Error: The signal is declared but never emitted. UNUSED_SIGNAL  #40496

[lostminds]

Thank you for your report, consolidating in #40496:

I do not think this is the same bug. The linked issue seems to be for a different problem from back in 3.x where you'd get the warning if you did not explicitly use emit_signal (but emitted it in some other way). This seems more complicated since it's hard to tell in this cases if the signal is emitted or not.

The reported issue is that you now get the warning even when using emit_signal explicitly in the same class script with the signal name like in the example above. This bug is also seems new to 4.3dev5 (or a regression), it's not present in 4.3dev4 or previous 4.x versions as far as I've experienced.

[dalexeev]

Yes, this is expected, which is why we added "explicitly" to the warning message. Note that you can use Signal.emit() (instead of Object.emit_signal()), which is a more recommended option.

We could add an exception for emit_signal(constant_string), however this will not work in case of dynamic expressions and something like call("emit_signal", "my_signal").

This bug is also seems new to 4.3dev5 (or a regression), it's not present in 4.3dev4 or previous 4.x versions

It's a bug fix, the UNUSED_SIGNAL warning was never produced before (in 4.x).

[lostminds]

I see, but then I think it could be a good idea to either add an exception for emit_signal("signal_name") for the specific signal (which I think could be seen as explicitly using the signal, even if technically it might not be) or be more clear in the warning that by explicit you mean using signal_name.emit() and that this is recommended.

Otherwise I think you might get a lot more confused bug reports like this one once 4.3 is released and more people start getting these warnings that were not they may perceptive as incorrect just like I did.