HTML rendering (_format=html) of expansions crashes with HTTP 500 in several renderer methods

[jmandel]

Summary

Requesting the human-readable HTML view (_format=html / Accept: text/html) of an otherwise-valid $expand crashes with HTTP 500 (uncaught errors in tx/library/renderer.js). At least two distinct triggers, plus a couple more wrong-key derefs in the same file.

Honest scope: HTML rendering is not a normatively-required FHIR representation, so this is a robustness/quality issue rather than a spec-conformance violation. Filed because a valid operation shouldn't 500 just because the HTML view was requested. Same class as the (closed) #175 renderer crash.

Repro A (live) — meta.version set → this.displayDate is not a function

curl -sS -X POST 'https://tx.fhir.org/r4/ValueSet/$expand?_format=html' \
  -H 'Content-Type: application/fhir+json' -w '\nHTTP %{http_code}\n' -d '{
  "resourceType":"Parameters","parameter":[{"name":"valueSet","resource":{
    "resourceType":"ValueSet","url":"http://example.org/f50","status":"active",
    "meta":{"version":"MV-XYZ"},
    "compose":{"include":[{"system":"http://hl7.org/fhir/account-status"}]}}},{"name":"count","valueInteger":1}]}'
# => HTTP 500 (Internal Server Error)

renderMetadataLastUpdated (entered from renderMetadataTable when meta.version is set) calls this.displayDate(...), which is not a method.

Repro B (live) — valueset-supplement extension → renderCompose passes the Extension object as a uri

curl -sS -X POST 'https://tx.fhir.org/r4/ValueSet/$expand?_format=html' \
  -H 'Content-Type: application/fhir+json' -w '\nHTTP %{http_code}\n' -d '{
  "resourceType":"Parameters","parameter":[{"name":"valueSet","resource":{
    "resourceType":"ValueSet","url":"http://example.org/f54","status":"active",
    "extension":[{"url":"http://hl7.org/fhir/StructureDefinition/valueset-supplement",
                  "valueCanonical":"http://hl7.org/fhir/CodeSystem/example-supplement"}],
    "compose":{"include":[{"system":"http://hl7.org/fhir/CodeSystem/example"}]}}},
    {"name":"includeDefinition","valueBoolean":true},{"name":"count","valueInteger":2}]}'
# => HTTP 500 (Internal Server Error)

The renderCompose supplements loop passes the whole valueset-supplement Extension object to renderLinkComma as the uri (it should pass getValuePrimitive(ext)), so resolveURL does system.includes('|') on an object → throw.

Also in renderer.js (same class, likely same surface)

• renderMetadataLabels calls this.renderCodin(...) (typo for renderCoding) when meta.label.length > 1.
• renderCoding / renderLinkComma destructure {desc, url} from resolveCode/resolveURL, which return {link, description} (and resolveURL is async) — wrong keys + a null destructure when no linkResolver.

Expected

The HTML view renders (or degrades gracefully); a valid $expand should not 500 because HTML was requested.

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Confirmed live against https://tx.fhir.org on 2026-06-06 (software FHIRsmith 0.9.6). Source line refs are from the published main branch.

[grahamegrieve]

fixed