feat: Add full support for ValueSet filter operators in InMemoryTerminologyServerValidationSupport (#6904)

* feat: add full support for ValueSet filters in in-memory terminology validation

This adds support for all FHIR-defined ValueSet filter operators
(e.g. is-a, descendent-of, is-not-a, in, regex, exists, etc.) to the in-memory
terminology validator (InMemoryTerminologyServerValidationSupport).

Supports:
- Structural filters: is-a, descendent-of, is-not-a, generalizes, child-of, descendent-leaf
- Equality/regex/inclusion: equal (=), regex, in, not-in
- Existence: exists

Adds internal indexing for concept code/display fields to enable efficient traversal
and matching. Follows case-sensitivity rules defined by CodeSystem.

Also includes a full unit test suite for all filters, covering both code and display
properties where relevant.

Fixes issues where descendant-based filters were not honored during expansion in
tests relying on in-memory terminology (e.g. no JPA preload).

Fixes #4447, #6255

* fix(validation): error on filtered ValueSet includes against ignored CodeSystem

When a ValueSet include specifies filters (e.g. “is-a”) but the referenced CodeSystem is
configured as NOT_PRESENT/ignored, in-memory expansion cannot apply structural filters.
Add a guard to throw an ExpansionCouldNotBeCompletedInternallyException in this scenario
rather than silently returning an empty result.

* test(validation): expect in-memory validation to fail for delta-based hierarchy

Previously we asserted success on an in-memory hierarchy check, but the expander
cannot apply ISA filters against a NOT_PRESENT CodeSystem patched only via
`$apply-codesystem-delta-add`. Update the test to assert that
`validateCode(...)` returns a non-OK outcome containing “cannot apply filters”
for the in-memory pass, then continue to validate via the deferred/pre-expanded path.

Author: iyt-trifork

hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/dao/r4/FhirResourceDaoR4ValueSetTest.java

@@ -141,17 +141,10 @@ public void testValidateCodeInValueSet_HierarchicalAndEnumeratedValueset() {
 		ValidationSupportContext ctx = new ValidationSupportContext(myValidationSupport);
 		ConceptValidationOptions options = new ConceptValidationOptions();
 
-		// In memory - Hierarchy in existing CS
-
-		outcome = myValidationSupport.validateCode(ctx, options, "http://cs", "child10", null, "http://vs");
-		assertNotNull(outcome);
-		assertTrue(outcome.isOk());
-		assertEquals("Code was validated against in-memory expansion of ValueSet: http://vs", outcome.getSourceDetails());
-
 		outcome = myValidationSupport.validateCode(ctx, options, "http://cs", "childX", null, "http://vs");
 		assertNotNull(outcome);
 		assertFalse(outcome.isOk());
-		assertThat(outcome.getMessage()).contains("Unknown code 'http://cs#childX' for in-memory expansion of ValueSet 'http://vs'");
+		assertThat(outcome.getMessage()).contains("cannot apply filters");
 
 		// In memory - Enumerated in non-present CS
 
@@ -248,13 +241,13 @@ public void testValidateCodeInValueSet_HierarchicalAndEnumeratedValueset_Hiberna
 
 		outcome = myValidationSupport.validateCode(ctx, options, "http://cs", "child10", null, "http://vs");
 		assertNotNull(outcome);
-		assertTrue(outcome.isOk());
-		assertEquals("Code was validated against in-memory expansion of ValueSet: http://vs", outcome.getSourceDetails());
+		assertFalse(outcome.isOk());
+		assertThat(outcome.getMessage()).contains("cannot apply filters");
 
 		outcome = myValidationSupport.validateCode(ctx, options, "http://cs", "childX", null, "http://vs");
 		assertNotNull(outcome);
 		assertFalse(outcome.isOk());
-		assertThat(outcome.getMessage()).contains("Unknown code 'http://cs#childX' for in-memory expansion of ValueSet 'http://vs'");
+		assertThat(outcome.getMessage()).contains("cannot apply filters");
 
 		// In memory - Enumerated in non-present CS
 

hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/support/InMemoryTerminologyServerValidationSupport.java

@@ -1021,6 +1021,26 @@ private boolean expandValueSetR5IncludeOrExclude(
 			boolean isIncludeCodeSystemIgnored = includeOrExcludeSystemResource != null
 					&& includeOrExcludeSystemResource.getContent() == Enumerations.CodeSystemContentMode.NOTPRESENT;
 
+			boolean isIncludeFromSystem = isNotBlank(theInclude.getSystem())
+					&& theInclude.getValueSet().isEmpty();
+			boolean isIncludeWithFilter = !theInclude.getFilter().isEmpty();
+
+			// if we can’t load the CS and we’re configured to ignore it...
+			if (isIncludeCodeSystemIgnored && !theInclude.getFilter().isEmpty()) {
+				// We can’t apply any structural (ISA/DESCENDENT-OF/etc..) filters if the CS is absent → fail
+				String msg = "Unable to expand ValueSet: cannot apply filters '" + theInclude.getFilter()
+						+ "' because CodeSystem '" + theInclude.getSystem()
+						+ "' is ignored/not-present";
+
+				throw new ExpansionCouldNotBeCompletedInternallyException(
+						Msg.code(2646) + msg,
+						new CodeValidationIssue(
+								msg,
+								IssueSeverity.ERROR,
+								CodeValidationIssueCode.NOT_FOUND,
+								CodeValidationIssueCoding.NOT_FOUND));
+			}
+
 			if (includeOrExcludeSystemResource == null || isIncludeCodeSystemIgnored) {
 
 				if (theWantCode != null) {
@@ -1097,9 +1117,6 @@ private boolean expandValueSetR5IncludeOrExclude(
 						}
 					}
 				} else {
-					boolean isIncludeFromSystem = isNotBlank(theInclude.getSystem())
-							&& theInclude.getValueSet().isEmpty();
-					boolean isIncludeWithFilter = !theInclude.getFilter().isEmpty();
 					if (isIncludeFromSystem && !isIncludeWithFilter) {
 						if (isIncludeWithDeclaredConcepts) {
 							theInclude.getConcept().stream()
@@ -1180,22 +1197,24 @@ private boolean expandValueSetR5IncludeOrExclude(
 		}
 
 		boolean retVal = false;
+		ValueSetExpansionFilterContext valueSetExpansionFilterContext =
+				new ValueSetExpansionFilterContext(includeOrExcludeSystemResource, theInclude.getFilter());
 
 		for (FhirVersionIndependentConcept next : nextCodeList) {
 			if (includeOrExcludeSystemResource != null && theWantCode != null) {
-				boolean matches;
-				if (includeOrExcludeSystemResource.getCaseSensitive()) {
-					matches = theWantCode.equals(next.getCode());
-				} else {
-					matches = theWantCode.equalsIgnoreCase(next.getCode());
-				}
+				boolean matches = includeOrExcludeSystemResource.getCaseSensitive()
+						? theWantCode.equals(next.getCode())
+						: theWantCode.equalsIgnoreCase(next.getCode());
+
 				if (!matches) {
 					continue;
 				}
 			}
 
-			theConsumer.accept(next);
-			retVal = true;
+			if (!valueSetExpansionFilterContext.isFiltered(next)) {
+				theConsumer.accept(next);
+				retVal = true;
+			}
 		}
 
 		return retVal;