Fix selection-filter panics when no test is supplied #22

select, reject, selectattr, and rejectattr support using truthiness when no explicit test is supplied. Those calls can currently panic while extracting optional test arguments.

{{ [0, 1, 2] | select | list }}
{{ [0, 1, 2] | reject | list }}
{{ [{'enabled': true}, {'enabled': false}] | selectattr('enabled') | list | length }}
{{ [{'enabled': true}, {'enabled': false}] | rejectattr('enabled') | list | length }}

Expected Python Jinja2 output:

[1, 2]
[0]
1
1

The implementation slices past the available arguments before the default truthiness behaviour gets a chance to run.

I’m raising a small PR to check the argument count before slicing and use an empty argument list when no additional test arguments are present. Explicit tests and their arguments will continue to pass through unchanged.

I’ll attach the PR here shortly, with regression tests for all four default-test forms.