LEGLINK-582: Omit the MeasureReport locator when the MeasureReport has no id (#1755)

resolveMeasureReport derives the ref's id from getIdElement().getIdPart(), which
returns null for a MeasureReport carrying no id. The locator guard only checked
that the ref itself was non-null, so a non-null ref with a null id reached
String.format and emitted

    Bundle.entry[0].resource.ofType(MeasureReport).where(id = 'null').extension[0]

— valid FHIRPath that resolves to nothing. The issue still looked well-formed, so
a dead locator would ship in submitted output with nothing logged. The null-ref
path warned; the null-id path did not.

- Require a non-null id alongside the non-null ref, falling through to the
  existing omission path. Broaden the warning to "No identifiable MeasureReport",
  since it now covers both causes.
- Rename build_nullMeasureReportId_omitsLocatorButKeepsResultExpressions to
  build_noMeasureReportRef_...: it passes null for the whole ref, so despite its
  name it never covered a null id. That misnaming is why the gap survived review.
- Add build_measureReportWithNullId_... for the case the old name claimed, and
  resolveMeasureReport_measureReportWithoutId_yieldsRefWithNullId to pin the
  source of the null id, so the guard is re-examined rather than silently
  orphaned if resolution ever starts synthesizing an id.

Raised by CodeRabbit on #1753 after it merged, hence the follow-up branch.

Testing: mvn -pl validation -am test on JDK 17, 131 tests pass (0 failures, 0
errors); PreQualOperationOutcomeBuilderTest grew 17 -> 19. The new null-id test
was confirmed to fail without the guard, reproducing where(id = 'null') exactly,
so it pins the fix rather than passing vacuously.

Author: MikeAtPinnacle

Java/validation/src/main/java/com/lantanagroup/link/validation/services/PreQualOperationOutcomeBuilder.java

@@ -96,11 +96,14 @@ public Optional<OperationOutcome> build(List<Result> results, MeasureReportRef m
             issue.addExtension(new Extension(PQ_ISSUE_CAT_URL, new CodeType(categoryId)));
 
             if (writeExpressions) {
-                if (measureReport != null) {
+                // The id is checked as well as the ref: a MeasureReport carrying no id yields a non-null
+                // ref with a null id, and formatting that produces where(id = 'null') — valid FHIRPath
+                // that silently resolves to nothing. Omitting the locator is the honest outcome.
+                if (measureReport != null && measureReport.id() != null) {
                     issue.addExpression(
                             String.format(MEASURE_REPORT_LOCATOR, measureReport.index(), measureReport.id()));
                 } else {
-                    _logger.warn("No MeasureReport in the bundle; omitting the MeasureReport locator expression");
+                    _logger.warn("No identifiable MeasureReport in the bundle; omitting the MeasureReport locator expression");
                 }
                 categoryResults.forEach(r -> issue.addExpression(r.getExpression()));
             }

Java/validation/src/test/java/com/lantanagroup/link/validation/services/PreQualOperationOutcomeBuilderTest.java

@@ -199,7 +199,7 @@ void build_writeExpressionsFalse_omitsAllExpressions() {
     }
 
     @Test
-    void build_nullMeasureReportId_omitsLocatorButKeepsResultExpressions() {
+    void build_noMeasureReportRef_omitsLocatorButKeepsResultExpressions() {
         Result r1 = result("msg", "result-expr", category("inactive_code", false));
 
         OperationOutcome oo = builder.build(List.of(r1), null, true).orElseThrow();
@@ -208,10 +208,40 @@ void build_nullMeasureReportId_omitsLocatorButKeepsResultExpressions() {
         assertEquals(List.of("result-expr"), expressions);
     }
 
+    @Test
+    void build_measureReportWithNullId_omitsLocatorButKeepsResultExpressions() {
+        // A MeasureReport with no id resolves to a non-null ref whose id is null. Formatting that would
+        // emit where(id = 'null') — valid FHIRPath that resolves to nothing, i.e. a silently dead locator
+        // in submitted output. The locator must be omitted instead.
+        Result r1 = result("msg", "result-expr", category("inactive_code", false));
+        PreQualOperationOutcomeBuilder.MeasureReportRef ref =
+                new PreQualOperationOutcomeBuilder.MeasureReportRef(0, null);
+
+        OperationOutcome oo = builder.build(List.of(r1), ref, true).orElseThrow();
+
+        List<String> expressions = expressionStrings(oo.getIssueFirstRep());
+        assertEquals(List.of("result-expr"), expressions);
+        assertFalse(expressions.stream().anyMatch(e -> e.contains("null")),
+                "Locator must not be emitted with a null id");
+    }
+
     // -------------------------------------------------------------------------
     // MeasureReport resolution (index + id)
     // -------------------------------------------------------------------------
 
+    @Test
+    void resolveMeasureReport_measureReportWithoutId_yieldsRefWithNullId() {
+        // Pins the source of the null id the builder has to defend against.
+        Bundle bundle = new Bundle();
+        bundle.addEntry().setResource(new MeasureReport());
+
+        PreQualOperationOutcomeBuilder.MeasureReportRef ref = builder.resolveMeasureReport(bundle);
+
+        assertNotNull(ref);
+        assertEquals(0, ref.index());
+        assertNull(ref.id());
+    }
+
     @Test
     void resolveMeasureReport_returnsIndexAndIdWhenFirstEntry() {
         Bundle bundle = new Bundle();