Fix multi-component stratifier alignment for list + scalar

cqf-fhir-cr/src/main/java/org/opencds/cqf/fhir/cr/measure/common/MeasureMultiSubjectEvaluator.java

@@ -412,10 +412,11 @@ private static List<StratumDef> buildValueOrNonSubjectValueStrata(
      *       to match function row keys when mixed with function components.</li>
      * </ul>
      *
-     * <h3>Mixed Function and Scalar Components</h3>
-     * <p>When a stratifier has both function components (per-resource) and scalar components (per-subject),
-     * the scalar values are expanded to match the function row keys. This ensures all components align
-     * for proper grouping.
+     * <h3>Mixed Multi-Value and Scalar Components</h3>
+     * <p>When a stratifier has both multi-value components (function results per-resource OR iterable
+     * results per-subject) and scalar components (per-subject), the scalar values are expanded to match
+     * the multi-value row keys. This ensures all components align for proper grouping so that each
+     * resulting stratum contains a value from every declared component.
      *
      * <h4>Example: Stratifier with 3 components</h4>
      * <ul>
@@ -466,12 +467,14 @@ private static Table<StratifierRowKey, StratumValueWrapper, StratifierComponentD
         final Table<StratifierRowKey, StratumValueWrapper, StratifierComponentDef> subjectResultTable =
                 HashBasedTable.create();
 
-        // First pass: Collect all composite row keys (subject|resource) from function components
-        // These are needed to expand scalar components to match function row keys
-        final Map<String, Set<StratifierRowKey>> functionRowKeysBySubject = collectFunctionRowKeys(componentDefs);
+        // First pass: Collect alignment row keys from multi-value components (function Maps and
+        // iterable Lists). These are needed to expand scalar components so every alignment row
+        // carries a value from every declared component, producing one stratum per alignment row
+        // rather than one stratum per (subject, component) pair.
+        final Map<String, Set<StratifierRowKey>> alignmentRowKeysBySubject = collectAlignmentRowKeys(componentDefs);
 
         for (StratifierComponentDef componentDef : componentDefs) {
-            for (StratumTableRow stratumTableRow : mapToListOfTableEntries(componentDef, functionRowKeysBySubject)) {
+            for (StratumTableRow stratumTableRow : mapToListOfTableEntries(componentDef, alignmentRowKeysBySubject)) {
                 subjectResultTable.put(
                         stratumTableRow.stratifierRowKey(), stratumTableRow.stratumValueWrapper(), componentDef);
             }
@@ -481,54 +484,75 @@ private static Table<StratifierRowKey, StratumValueWrapper, StratifierComponentD
     }
 
     /**
-     * Collects all composite row keys (subject|resource) from function components.
+     * Collects the row keys produced by multi-value components, keyed by subject. These are used
+     * to expand scalar components so every alignment row carries a value from every declared
+     * component.
      *
-     * <p>This is used to expand scalar components to match the function row keys when
-     * stratifiers mix function and scalar components.
+     * <p>Two kinds of multi-value components contribute keys:
+     * <ul>
+     *   <li><b>Function (Map) results</b> — composite {@code (subject | functionInput)} row keys,
+     *       one per input resource.</li>
+     *   <li><b>Iterable (List) results</b> — composite {@code (subject | iterableElement(value, index))}
+     *       row keys, one per list element. Aligning scalars to these keys is what allows a stratifier
+     *       declared with one iterable component and one scalar component to emit strata that contain
+     *       both component values, instead of one stratum per component value.</li>
+     * </ul>
      *
-     * @return Map from subject (e.g., "Patient/123") to set of composite row keys
+     * @return Map from subject (e.g., "Patient/123") to set of alignment row keys
      */
-    private static Map<String, Set<StratifierRowKey>> collectFunctionRowKeys(
+    private static Map<String, Set<StratifierRowKey>> collectAlignmentRowKeys(
             List<StratifierComponentDef> componentDefs) {
 
-        final Map<String, Set<StratifierRowKey>> functionRowKeysBySubject = new HashMap<>();
+        final Map<String, Set<StratifierRowKey>> alignmentRowKeysBySubject = new HashMap<>();
 
         for (StratifierComponentDef componentDef : componentDefs) {
             for (var entry : componentDef.getResults().entrySet()) {
-                String subjectId = entry.getKey();
-                CriteriaResult result = entry.getValue();
-                Object rawValue = result == null ? null : result.rawValue();
-
-                // Only process function results (Map values)
-                if (rawValue instanceof Map<?, ?> functionResults) {
-                    String qualifiedSubject = FhirResourceUtils.addPatientQualifier(subjectId);
-                    Set<StratifierRowKey> rowKeys =
-                            functionRowKeysBySubject.computeIfAbsent(qualifiedSubject, k -> new HashSet<>());
-
-                    for (Object key : functionResults.keySet()) {
-                        rowKeys.add(
-                                StratifierRowKey.withInput(qualifiedSubject, StratifierRowValue.ofFunctionInput(key)));
-                    }
-                }
+                collectAlignmentRowKeysForEntry(entry.getKey(), entry.getValue(), alignmentRowKeysBySubject);
             }
         }
 
-        return functionRowKeysBySubject;
+        return alignmentRowKeysBySubject;
+    }
+
+    private static void collectAlignmentRowKeysForEntry(
+            String subjectId, CriteriaResult result, Map<String, Set<StratifierRowKey>> alignmentRowKeysBySubject) {
+
+        final Object rawValue = result == null ? null : result.rawValue();
+        if (!(rawValue instanceof Map<?, ?>) && !(rawValue instanceof Iterable<?>)) {
+            return;
+        }
+
+        final String qualifiedSubject = FhirResourceUtils.addPatientQualifier(subjectId);
+        final Set<StratifierRowKey> rowKeys =
+                alignmentRowKeysBySubject.computeIfAbsent(qualifiedSubject, k -> new HashSet<>());
+
+        if (rawValue instanceof Map<?, ?> functionResults) {
+            for (Object key : functionResults.keySet()) {
+                rowKeys.add(StratifierRowKey.withInput(qualifiedSubject, StratifierRowValue.ofFunctionInput(key)));
+            }
+        } else {
+            int index = 0;
+            for (Object value : (Iterable<?>) rawValue) {
+                rowKeys.add(StratifierRowKey.withInput(
+                        qualifiedSubject, StratifierRowValue.ofIterableElement(value, index)));
+                index++;
+            }
+        }
     }
 
     private static List<StratumTableRow> mapToListOfTableEntries(
-            StratifierComponentDef componentDef, Map<String, Set<StratifierRowKey>> functionRowKeysBySubject) {
+            StratifierComponentDef componentDef, Map<String, Set<StratifierRowKey>> alignmentRowKeysBySubject) {
 
         return componentDef.getResults().entrySet().stream()
-                .map(entry -> mapToListOfTableEntries(entry.getKey(), entry.getValue(), functionRowKeysBySubject))
+                .map(entry -> mapToListOfTableEntries(entry.getKey(), entry.getValue(), alignmentRowKeysBySubject))
                 .flatMap(Collection::stream)
                 .toList();
     }
 
     private record StratumTableRow(StratifierRowKey stratifierRowKey, StratumValueWrapper stratumValueWrapper) {}
 
     private static List<StratumTableRow> mapToListOfTableEntries(
-            String subjectId, CriteriaResult result, Map<String, Set<StratifierRowKey>> functionRowKeysBySubject) {
+            String subjectId, CriteriaResult result, Map<String, Set<StratifierRowKey>> alignmentRowKeysBySubject) {
 
         final String qualifiedSubject = FhirResourceUtils.addPatientQualifier(subjectId);
         final Object rawValue = result == null ? null : result.rawValue();
@@ -540,33 +564,41 @@ private static List<StratumTableRow> mapToListOfTableEntries(
             return addIterableValueRows(qualifiedSubject, iterableValue);
         }
 
-        // Scalar value: check if we need to expand to match function row keys
-        Set<StratifierRowKey> functionRowKeys = functionRowKeysBySubject.get(qualifiedSubject);
-        if (CollectionUtils.isNotEmpty(functionRowKeys)) {
-            // Expand scalar to match function row keys for this subject
-            return expandScalarToMatchFunctionRowKeys(functionRowKeys, rawValue);
+        // Scalar value: expand to match the alignment row keys produced by any multi-value
+        // components (functions or iterables) on this subject, so the scalar lands in every stratum.
+        Set<StratifierRowKey> alignmentRowKeys = alignmentRowKeysBySubject.get(qualifiedSubject);
+        if (CollectionUtils.isNotEmpty(alignmentRowKeys)) {
+            return expandScalarToAlignmentRowKeys(alignmentRowKeys, rawValue);
         }
 
-        // No function row keys - use simple subject-only row key
+        // If the stratifier as a whole has multi-value components but this particular subject
+        // produced no alignment rows (empty Map / empty List), the subject contributes no
+        // stratum at all — same semantic as the single-component empty-list case. Otherwise
+        // (purely scalar stratifier), fall back to a subject-only row key.
+        if (!alignmentRowKeysBySubject.isEmpty()) {
+            return List.of();
+        }
         return List.of(addScalarValueRow(qualifiedSubject, rawValue));
     }
 
     /**
-     * Expands a scalar value to match the row keys from function components.
+     * Expands a scalar value to match the alignment row keys produced by multi-value components
+     * (function Maps or iterable Lists).
      *
-     * <p>When stratifiers mix function and scalar components, the scalar value applies
-     * to all resources for that subject. This method creates one row per function row key,
-     * all with the same scalar value.
+     * <p>When stratifiers mix multi-value and scalar components, the scalar value applies to every
+     * alignment row for that subject. Emitting one table row per alignment key, all with the same
+     * scalar value, lets the downstream group-by-value-set step produce strata where each stratum
+     * contains a value from every declared component.
      *
-     * @param functionRowKeys the row keys from function components for this subject
+     * @param alignmentRowKeys the row keys from multi-value components for this subject
      * @param scalarValue the scalar value to expand
-     * @return list of table rows, one per function row key
+     * @return list of table rows, one per alignment row key
      */
-    private static List<StratumTableRow> expandScalarToMatchFunctionRowKeys(
-            Set<StratifierRowKey> functionRowKeys, Object scalarValue) {
+    private static List<StratumTableRow> expandScalarToAlignmentRowKeys(
+            Set<StratifierRowKey> alignmentRowKeys, Object scalarValue) {
 
         StratumValueWrapper valueWrapper = new StratumValueWrapper(scalarValue);
-        return functionRowKeys.stream()
+        return alignmentRowKeys.stream()
                 .map(rowKey -> new StratumTableRow(rowKey, valueWrapper))
                 .toList();
     }

cqf-fhir-cr/src/test/java/org/opencds/cqf/fhir/cr/measure/r4/MeasureStratifierTest.java

@@ -1505,4 +1505,139 @@ void cohortBooleanValueStratListExpressionInvalid() {
                 .hasContainedOperationOutcomeMsg(
                         "value stratifier is invalid for expression: [All Encounters] with result types: [Encounter] for measure URL: http://example.com/Measure/CohortBooleanValueStratListExpression. Expected a scalar type");
     }
+
+    /**
+     * boolean (subject) basis stratifier with two components — one returning a
+     * per-patient {@code List} ("Distinct Encounter Statuses") and one returning a per-patient
+     * scalar ("Gender Stratification String") — must emit one stratum per unique
+     * (list-element, scalar) tuple, with each stratum carrying BOTH component values.
+     * <p/>
+     * Before the fix, scalar components were only expanded to align with function (Map) row keys,
+     * never iterable row keys, so the iterable's composite row key and the scalar's subject-only
+     * row key landed in disjoint groups — producing one stratum per component value with only that
+     * single component, instead of strata with both components.
+     * <p/>
+     * Patient-9 has two Encounters (statuses {@code finished}, {@code in-progress}) and gender
+     * {@code male}, so two strata are expected:
+     * <ul>
+     *   <li>{Encounter Status: finished, Gender: male} — count 1</li>
+     *   <li>{Encounter Status: in-progress, Gender: male} — count 1</li>
+     * </ul>
+     */
+    @Test
+    void cohortBooleanMultiComponentListScalarStratPatient9() {
+        GIVEN_MEASURE_STRATIFIER_TEST
+                .when()
+                .measureId("CohortBooleanMultiComponentListScalarStrat")
+                .subject("Patient/patient-9")
+                .evaluate()
+                .then()
+                .firstGroup()
+                .firstStratifier()
+                .hasCodeText("Encounter Status and Gender")
+                .hasStratumCount(2)
+                .stratum(s -> s.getStratum().stream()
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "finished".equals(c.getValue().getText())))
+                        .findFirst()
+                        .orElse(null))
+                .hasComponentStratifierCount(2)
+                .stratumComponentWithCodeText("Encounter Status")
+                .hasValueText("finished")
+                .up()
+                .stratumComponentWithCodeText("Gender")
+                .hasValueText("male")
+                .up()
+                .firstPopulation()
+                .hasCount(1)
+                .up()
+                .up()
+                .stratum(s -> s.getStratum().stream()
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "in-progress".equals(c.getValue().getText())))
+                        .findFirst()
+                        .orElse(null))
+                .hasComponentStratifierCount(2)
+                .stratumComponentWithCodeText("Encounter Status")
+                .hasValueText("in-progress")
+                .up()
+                .stratumComponentWithCodeText("Gender")
+                .hasValueText("male")
+                .up()
+                .firstPopulation()
+                .hasCount(1);
+    }
+
+    /**
+     * multi-subject variant of {@link #cohortBooleanMultiComponentListScalarStratPatient9()}.
+     * Across all patients (data per {@code cohortBooleanValueStratMultiValueListOverlapping}),
+     * the stratifier must produce one stratum per unique (encounter-status, gender) tuple, each
+     * with two components. The expected tuples are:
+     * <pre>
+     * (in-progress, female)  → patient-0
+     * (in-progress, male)    → patient-1, patient-9
+     * (finished,   female)   → patient-0, patient-8
+     * (finished,   male)     → patient-1, patient-9
+     * (arrived,    female)   → patient-2
+     * (arrived,    male)     → patient-3
+     * (triaged,    female)   → patient-4
+     * (triaged,    male)     → patient-5
+     * (cancelled,  female)   → patient-6
+     * (cancelled,  male)     → patient-7
+     * </pre>
+     */
+    @Test
+    void cohortBooleanMultiComponentListScalarStratAllPatients() {
+        GIVEN_MEASURE_STRATIFIER_TEST
+                .when()
+                .measureId("CohortBooleanMultiComponentListScalarStrat")
+                .evaluate()
+                .then()
+                .firstGroup()
+                .firstStratifier()
+                .hasCodeText("Encounter Status and Gender")
+                .hasStratumCount(10)
+                .stratum(s -> s.getStratum().stream()
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "finished".equals(c.getValue().getText())))
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "male".equals(c.getValue().getText())))
+                        .findFirst()
+                        .orElse(null))
+                .hasComponentStratifierCount(2)
+                .firstPopulation()
+                .hasCount(2) // patient-1, patient-9
+                .up()
+                .up()
+                .stratum(s -> s.getStratum().stream()
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "finished".equals(c.getValue().getText())))
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "female".equals(c.getValue().getText())))
+                        .findFirst()
+                        .orElse(null))
+                .hasComponentStratifierCount(2)
+                .firstPopulation()
+                .hasCount(2) // patient-0, patient-8
+                .up()
+                .up()
+                .stratum(s -> s.getStratum().stream()
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "cancelled".equals(c.getValue().getText())))
+                        .filter(st -> st.getComponent().stream()
+                                .anyMatch(c -> c.hasValue()
+                                        && "male".equals(c.getValue().getText())))
+                        .findFirst()
+                        .orElse(null))
+                .hasComponentStratifierCount(2)
+                .firstPopulation()
+                .hasCount(1); // patient-7
+    }
 }