How can I programmatically access zsh completion?

Question

zsh has a completion system, activated by pressing tab:

llama@llama:~$ git st<Tab>
Completing main porcelain command
stash      -- stash away changes to dirty working directory
status     -- show working-tree status
Completing plumbing internal helper command
stripspace -- filter out empty lines

All I've been able to figure out is that this comes from the script /usr/share/zsh/functions/Completion/Unix/_git, where _git is the completion command being called.

Assuming I know the name of the completion function (e.g. _git), how could I get the output of what would happen if I entered a certain string and pressed tab? Essentially, I'm trying to take an input of ex. git st and get the output above (programmatically, from a script).

There are many other existing questions about this for bash, but I haven't found anything explaining how to achieve this with zsh.

Answer 1

This can be done by using zsh-capture-completion. The repository's README.md file provides several examples:

capture.zsh 'vim -'
capture.zsh 'vim --'
capture.zsh 'vim --r'
capture.zsh 'echo *('
capture.zsh 'scp hostname:'

Note that the package itself states that it is a proof of concept, and as such may contain errors in its execution.