fix: return empty collection when join() is called on empty collection (Fixes #65)#74
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…alled on empty collection Per the FHIRPath specification, join() on an empty collection should return an empty collection, not an empty string: https://build.fhir.org/ig/HL7/FHIRPath/#joinseparator-string--string Previously, separator.join([]) would return '' which was returned directly. Now we check for an empty collection and return [] before calling join. Fixes beda-software#65
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Fixes #65
Problem
Per the FHIRPath specification,
join()applied to an empty collection should return an empty collection, not an empty string:Previously, the
joinfunction calledseparator.join([])which returns"", and this empty string was returned directly — violating the spec.Solution
Added an empty collection check at the beginning of the
joinfunction infhirpathpy/engine/invocations/strings.py. When the input collection is empty, the function now returns[]instead of"".This is consistent with how all other FHIRPath functions in this codebase handle empty collections (e.g.,
matches,replace,contains, etc. all return[]for empty inputs).Verification
All 5 new join tests pass (empty + non-empty cases) alongside the existing 1652 tests.
About the Author: Raphael Malikian — Clinical AI Solutions Architect. I specialise in building and fixing AI/ML systems for healthcare, including vector databases, RAG pipelines, and clinical NLP. If you need help with your project or think I can add value to your organisation, feel free to reach out — I'd love to connect.
📧 rtmalikian@gmail.com
🔗 GitHub: https://github.com/rtmalikian
🔗 LinkedIn: http://www.linkedin.com/in/raphael-t-malikian-mbbs-bsc-hons-71075436a
Disclosure: This code was developed with assistance from mimo-2.5-pro (Xiaomi) via Hermes Agent (Nous Research). All changes were reviewed, tested against the actual codebase, and verified for correctness.