Is the argument list of a signal meaningless?

leonhardt

This code snippet can run without any error or warning. It seems that the signal object does not check the number of parameters of its connected functions. So, the argument list is redundant???

kuligs2

leonhardt its not if you want intellisense to show you what to pass into the signal, other than that imo yes

Dodo_87

For those, who wonder: Static typing does not add any value beyond documentation, as well. The following example compiles without any error.

extends Node

signal test_signal(a: int)

func _ready():
	test_signal.connect(func (a: String): print(a)) # connect a non-matching Callable
	test_signal.emit("abc") # pass non-matching argument (wrt. test_signal)
	test_signal.emit(false) # pass non-matching argument (wrt. Callable and test_signal)

The last line causes a runtime error, because the arguments do not match those of the Callable, though.

leonhardt

The argument list of signal is only useful for documentation purposes. See also https://github.com/godotengine/godot/issues/54333#issuecomment-1502908418.

kuligs2

leonhardt for that reason its very usefull.. i myself try to comment things but i sometimes am too lazy to bother, and after months of hiatus, getting back is very hard 😃

leonhardt

kuligs2 Yes, that's true. However, if you make a mistake when declaring a signal, it can be quite confusing when you revisit the code later. Something apparently not correct, but it works right...

And, consider the following scenario:

extends Control

signal test_signal3(a, b, c, d, e, f, g)

func _ready():
    # suppose this is located in another script
    test_signal3.connect(func(a, b): print("test_signal3:", a, b))

    # you use this signal following the signal signature
    test_signal3.connect(func(a, b, c, d, e, f, g): print("test_signal3:", a, b, c, d, e, f, g))
    test_signal3.emit(1,2,3,4,5,6,7)
    # then you will get the right output with a very confusing error: Error calling from signal 'test_signal3' to callable: 'GDScript::<anonymous lambda>': Method expected 2 arguments, but called with 7.

So I think the number of parameters should at least be checked for correctness. It seems like this isn't such an easy thing to do..

DaveTheCoder

From reading the github issues relating to this, my conclusion is that fixing this requires someone to implement it and submit a Pull Request.