On my Spigot server I found I was unable to tab complete the /give command. I was told by md_5 that tab completion only works on vanilla commands so if a plugin overrides the command it will not work. Using /minecraft:give works as I would have expected.

I then tried to use the provided commands.yml file to alias /give to the vanilla version of the give command to try to get around a plugin overriding the command causing tab completion not to work.

Example:

give:
    - "minecraft:give $1-"

This did not work however even though I confirmed I made no typos when defining the alias. So I then went on to remove ALL plugins to ensure there were no plugins that could override the give command. I left the alias defined in commands.yml and I found that just this alone caused the tab completion not to work. As soon as I removed the alias defined in commands.yml and had no plugins it began working again.

This means that the alias is unable to forward the tab completion down to the command defined in the alias even though the command defined would normally work with tab completion.

Its mostly a QOL issue and an annoyance but I consider it a bug as the alias system should be able to support tab completion. Whether this would be something that can be fixed or not i'm not sure.