Completions not erasing with complete -c <command> -e #6716
Description
I have been investigating a large slowdown in git completions in 3.1 on Windows (running under msys2), where completion times have ballooned out to between 3-10 seconds for some commands.
In doing so I have noticed that I seem unable to erase completion rules in a shell until they have actually been used. For example, in a fresh shell
$ sh -c 'env HOME=$(mktemp -d) fish'
Welcome to fish, the friendly interactive shell
Type `help` for instructions on how to use fish
$ fish --version
fish, version 3.1.0
# we think we are erasing the completion rules
$ complete -c git -e
# but this generates a tonne of completions (and is *very* slow)
$ complete -C"git checkout " | wc -l
1524
# try erasing again
$ complete -c git -e
# now it behaves as expected
$ complete -C"git checkout " | wc -l
56
I've observed the same behaviour, in terms of rules not being erased until having somehow been used, in 3.0.2 on RHEL7.5. This does not feel like "expected" behaviour.