Summary

Prevent Caliper events from dying on problem-group pseudo source files.

Problems selected from a problem group carry the pseudo source file group:problemGroupName (see WeBWorK::Utils::Instructor::assignProblemToUserSetVersion), which is not a real file under the course templates directory. Caliper::Entity::problem unconditionally passed that path to WeBWorK::Utils::Tags->new, whose open ... or die kills the request. As a result, any Caliper event that embeds the problem entity — for example an answer-submission event in a gateway quiz built from problem groups — crashed server side whenever Caliper is enabled.

This change guards the tag-parsing block in sub problem so it is skipped for group: pseudo source files. For those problems the entity payload now reports keywords => [] and tags => undef. Real problem files are unaffected: WeBWorK::Utils::Tags initializes {keywords} to [] for every real .pg file it parses, so keywords is always an arrayref, and the keyword trimming and unblessed tag hash are built exactly as before.

Note that sub problem_user intentionally keeps the unguarded tag parsing: user problems for versioned (gateway) sets are assigned a concrete source file selected out of the group at set-version creation time, so a merged user problem never carries the group: pseudo path.

Testing

• Exercised Caliper::Entity::problem with the dependency surface stubbed (WeBWorK::DB, Caliper::ResourceIri, and a WeBWorK::Utils::Tags stub reproducing the real open ... or die behavior):
  • Before this change, a problem with source file group:myGroup dies with cannot open .../group:myGroup: No such file or directory; after this change it returns a payload with keywords => [], extensions.tags => undef, and extensions.source_file passed through.
  • A real .pg source file produces an identical payload before and after the change (keywords trimmed of quotes/whitespace, unblessed tags hash populated).
  • A missing real (non-group:) source file still dies as before; this change does not swallow genuine errors.
• perl -c lib/Caliper/Entity.pm passes (with dependency stubs, since a full course environment is not available in the check environment).
• perltidy (Perl::Tidy 20260204, matching check-formats.yml) with the repo .perltidyrc produces no changes.

Dependencies

Depends on #3050 (this branch is based on it, since #3050 already touches the same region of lib/Caliper/Entity.pm with the Caliper::ResourceIri package rename and the showHintsAfter() fix).