is there a nice way to test click auto-completion functions?

[seebi]

The current documentation is blank about this.
Is there maybe an example somewhere?

[davidism]

To trigger autocompletion, your shell calls your program with the _PROG_NAME_COMPLETE=source env var. If you're using CliRunner, you can call invoke(..., env={"_FOO_COMPLETE": "source"}, prog_name="foo") along with partial arguments and look at the output, the same way the shell would.

Or test your autocompletion function directly, since Click's internals are already tested. An autocompletion function takes a Context, list of full arguments, and the partial string being completed, all of which you can fake in a test.

Click's own tests use a somewhat internal function: https://github.com/pallets/click/blob/master/tests/test_bashcomplete.py.

[seebi]

When I start it like this, I actually do not get my function output but something like

_cmemc_completion() {
    local IFS=$'
'
    COMPREPLY=( $( env COMP_WORDS="${COMP_WORDS[*]}" \
                   COMP_CWORD=$COMP_CWORD \
                   _CMEMC_COMPLETE=complete $1 ) )
    return 0
}

_cmemc_completionetup() {
    local COMPLETION_OPTIONS=""
    local BASH_VERSION_ARR=(${BASH_VERSION//./ })
    # Only BASH version 4.4 and later have the nosort option.
    if [ ${BASH_VERSION_ARR[0]} -gt 4 ] || ([ ${BASH_VERSION_ARR[0]} -eq 4 ] && [ ${BASH_VERSION_ARR[1]} -ge 4 ]); then
        COMPLETION_OPTIONS="-o nosort"
    fi

    complete $COMPLETION_OPTIONS -F _cmemc_completion cmemc
}

_cmemc_completionetup;

Do I miss something here?

[davidism]

Nope, that's what autocompletion does, then the your shell takes that and actually handles the completion. You probably want to test your custom function, which the other two options do.

[seebi]

Ok, got it ... using

from click._bashcomplete import get_choices

def choices_without_help(cli, args, incomplete):
    completions = get_choices(cli, 'cmemc', args, incomplete)
    return [c[0] for c in completions]

def test_delete_completion():
    assert choices_without_help(cli, ['graph', 'delete'], 'acc') == ['...']

actually does the job.... nice.

And thanks @davidism

[davidism]

Follow up to this, I mistyped. _PROG_NAME_COMPLETE=complete, not source, will make Click output the available completions. source outputs the shell function that enables completion, and you can see it calling Click with complete. Either way works for testing.