It is now possible to have custom completion for aliases, for example to complete with another command completion, or with your own completion.

Examples:

• create alias /forcejoin with completion of /sajoin: /alias -completion %%sajoin forcejoin /quote forcejoin
• create alias /mybuf with custom completion: /alias -completion #weechat|#weechat-fr mybuf /buffer

You can change completion if alias is already created:

/set alias.completion.forcejoin "%%sajoin"

You can use empty string to prevent any completion for command (default is to complete using target command):

/set alias.completion.forcejoin ""

And you can remove a completion:

/unset alias.completion.forcejoin

Completion is automatically removed when you remove an alias with /unalias.