Action's parameters are not being passed correctly

Describe the bug When you pass a list of parameters to an action, only the last parameter in the list is being received by the function. What’s more, the parameter is being “moved” to the first position.

<script>	
	function test (node, el1, el2, el3) {
		console.log(el1, el2, el3) // logs `third undefined undefined`, instead of `first second third`
	}
</script>

<h1 use:test={'first', 'second', 'third'}>Hello!</h1>

This used to work in 3.12.1 but it doesn’t work in 3.24.0

To Reproduce Open the this REPL and see the logs. Compare the logs with that one.

Expected behavior Parameters should be passed correctly.

[mindrones]

We agreed to rephrase a bit to clarify that actions can have just one parameter (although the signature is correct), re-opening.

[pngwn]

Multiple parameters working was a bug and we have fixed that now.

@yuliankarapetkov

I see, it used to work differently in 3.12.1 and then maybe in this case the log should show first, not third, right?

No, the current behaviour is expected. The argument you provide to an action is an expression that is passed as the second parameter to the action function:

<div use:fn={1, 2, 3} />

Is actually doing this:

fn(
  node, 
  (1, 2, 3)
)

Evaluating the expression (1, 2, 3) will return 3.