Lambda functions inside parenthesis inside an argument list result into invalid syntax

[CosmoMyzrailGorynych]

Godot 4.7.1, plugin version 0.22.0. (The formatter was run through CLI)

I wish this syntax worked, too, but unfortunately such formatting is not supported:

-	CheatPanel.add_cheat(&'heal_hero', 'Heal the hero', (func() -> void: health = max_health), self)
+	CheatPanel.add_cheat(
+		&'heal_hero',
+		'Heal the hero',
+		(func() -> void:
+			health = max_health
+		),
+		self,
+	)

Valid formatting example:

	CheatPanel.add_cheat(
		&'toggle_godmode',
		'Toggle godmode',
		(func() -> void:
			god_mode = !god_mode
			),
		self,
	)

or maybeeee

	CheatPanel.add_cheat(
		&'heal_hero',
		'Heal the hero',
		(func() -> void:
			health = max_health
			)
		,
		self,
	)

The parentheses around the lambda function can be dropped. (They were there initially to separate the function body from the 4th argument self: otherwise the , operator is parsed as the continuation of the function body.) But the trailing comma is quite error-prone.

	CheatPanel.add_cheat(
		&'heal_hero',
		'Heal the hero',
		func() -> void:
			health = max_health, # ← Easy to miss/erase
		self,
	)

[portlek]

I've encounter pretty much the same issue with much more simple syntax:

Input:

func _test() -> void:
    var test: = ((func (it: String) -> String: return it))

Output (correct):

func _test() -> void:
    var test := ((func(it: String) -> String:
        return it
    ))

Input-2:

func _test() -> void:
    [].map((func (it: String) -> String: return it))

Output-2 (broken):

func _test() -> void:
    [].map(
        (func(it: String) -> String:
            return it
        )
    )

[portlek]

@NathanLovato
New findings, probably related to this again:

Input:

func _test() -> void:
    var test: String = ", ".join([].map(func(it: String) -> String: return it))

Command:
gdscript-formatter --use-spaces --max-line-length 10 .\test.gd
--max-line-length 10 is only to simulate a long expression, not necessary.

Output

func _test() -> void:
    var test: String = ", ".join(
        [].map(
            func(
                it: String
            ) -> String:
                return it
        )
    )

I've a really big codebase that contains all sort of things including addons. I believe this is the only remaining code that breaks after i use the formatter.

[NathanLovato]

Thanks! It's related as it's due to lambdas; it's happening because the closing parenthesis belongs to the map() call so the formatter still tries to keep the map call itself neat. I'm gonna document it separately and think about what to do because it's one of those cases where the GDScript parser is not working very well and we have to work around its quirks.

The simplest definitive fix would probably be forcing trailing comma on the last line of the lambda and removing unnecessary surrounding parentheses but @CosmoMyzrailGorynych pointed out it can be error prone when editing the code. The next reliable thing would be wrapping the lambda in snug parentheses in cases like this:

(func(it: String):
    return it)

The reason for suggesting this is that this can be made consistent and reliable in all situations where a lambda is in parentheses. But we could also handle it on a per-case basis.

And great to hear it might be the last thing in your large codebase! Thanks for testing it there; I haven't had time to grab and test very large open source GDScript codebases just yet (first I'd like to find time to write and implement a complete spec for the desired line wrapping and spacing behavior, to ensure consistency; got a draft but needs work).