Allow to control trailing tokens when doing layer unpacking

[msjyoo]

In a macro expansion such as

function (·vars ··· { ·var , }) { return ·expr; }

It is impossible to specify the correct amount of commas (to my knowledge of YAY functionality) - the last match will always add a trailing comma which is invalid syntax.

On function calls this can be alleviated by using array destructuring ...[var, var, var, ] but function definitions do not have this workaround.

[marcioAlmada]

This one is listed on the roadmap issue #3. Basically we need an expander called ·ls (stands for list) that could be used this way ·ls(·vars, ',', YAY_NO_TRAILING). That would allow you to decide if a trailing separator (in your case a comma) should be added or not.

Or maybe we need syntax support on the current unpacking syntax to indicate how to make delimiters behave.

[marcioAlmada]

Expanders are declared here, btw https://github.com/marcioAlmada/yay/blob/master/src/expanders.php.

They are just functions that receive a TokenStream and return another TokenStream.

Tests for expanders are here: https://github.com/marcioAlmada/yay/tree/master/tests/phpt/expanders

[msjyoo]

@marcioAlmada What do you think about an IRC channel on freenode? Would you mind if I implemented some of the easy picks?

[marcioAlmada]

I'm currently in transit ✈️ so there won't be time to create a real time support channel withing the next 3 days. But feel free to get some easy picks. I'll try to reply ASAP.

[msjyoo]

Ah okay. Safe travels!

[marcioAlmada]

·implode(·vars, ',') is probably more self explanatory.

[marcioAlmada]

Turns out adding first class trailing token control to the already existing unpacking syntax ··· look way more expressive. See the tests at 397fb05.