default filter requires an explicit argument and fails without one #1339

The default filter declares default_value as a required parameter, so a template that uses the filter without an argument fails to render. Jinja2 makes the argument optional and supplies an empty string.

Affected: master df50b0d7. Releases 2.7.6, 2.8.3 and 2.8.4 carry the same declaration.

Reproduction

{{ 'a'|default }}

Jinja2 renders a. Jinjava raises:

com.hubspot.jinjava.interpret.FatalTemplateErrorsException: Argument named 'default_value' is required but missing for filter default

Root cause

DefaultFilter registers default_value with required = true. AbstractFilter.validateArgs rejects the call before the filter body runs, so no path returns the input unchanged when the argument is omitted.