Allow usage of variable and context in answer expression

datacapture/src/main/java/com/google/android/fhir/datacapture/expressions/EnabledAnswerOptionsEvaluator.kt

@@ -91,13 +91,19 @@ internal class EnabledAnswerOptionsEvaluator(
    */
   internal suspend fun evaluate(
     questionnaireItem: QuestionnaireItemComponent,
-    questionnaireResponseItem: QuestionnaireResponseItemComponent,
+    questionnaireResponseItem: QuestionnaireResponseItemComponent
   ): Pair<
     List<Questionnaire.QuestionnaireItemAnswerOptionComponent>,
     List<QuestionnaireResponse.QuestionnaireResponseItemAnswerComponent>
   > {
 
-    val resolvedAnswerOptions = answerOptions(questionnaireItem)
+    val resolvedAnswerOptions =
+      answerOptions(
+        questionnaireItem,
+        questionnaireResponseItem,
+        questionnaireResponse,
+        questionnaireItemParentMap
+      )
 
     if (questionnaireItem.answerOptionsToggleExpressions.isEmpty())
       return Pair(resolvedAnswerOptions, emptyList())
@@ -133,12 +139,21 @@ internal class EnabledAnswerOptionsEvaluator(
    */
   private suspend fun answerOptions(
     questionnaireItem: QuestionnaireItemComponent,
+    questionnaireResponseItem: QuestionnaireResponseItemComponent,
+    questionnaireResponse: QuestionnaireResponse,
+    questionnaireItemParentMap: Map<QuestionnaireItemComponent, QuestionnaireItemComponent>
   ): List<Questionnaire.QuestionnaireItemAnswerOptionComponent> =
     when {
       questionnaireItem.answerOption.isNotEmpty() -> questionnaireItem.answerOption
       !questionnaireItem.answerValueSet.isNullOrEmpty() ->
         resolveAnswerValueSet(questionnaireItem.answerValueSet)
-      questionnaireItem.answerExpression != null -> resolveAnswerExpression(questionnaireItem)
+      questionnaireItem.answerExpression != null ->
+        resolveAnswerExpression(
+          questionnaireItem,
+          questionnaireResponseItem,
+          questionnaireResponse,
+          questionnaireItemParentMap
+        )
       else -> emptyList()
     }
 
@@ -185,6 +200,9 @@ internal class EnabledAnswerOptionsEvaluator(
   // https://build.fhir.org/ig/HL7/sdc/expressions.html#x-fhir-query-enhancements
   private suspend fun resolveAnswerExpression(
     item: QuestionnaireItemComponent,
+    responseItem: QuestionnaireResponseItemComponent,
+    questionnaireResponse: QuestionnaireResponse,
+    questionnaireItemParentMap: Map<QuestionnaireItemComponent, QuestionnaireItemComponent>
   ): List<Questionnaire.QuestionnaireItemAnswerOptionComponent> {
     // Check cache first for database queries
     val answerExpression = item.answerExpression ?: return emptyList()
@@ -212,7 +230,7 @@ internal class EnabledAnswerOptionsEvaluator(
           )
       }
       answerExpression.isFhirPath -> {
-        val data = fhirPathEngine.evaluate(questionnaireResponse, answerExpression.expression)
+        val data = expressionEvaluator.evaluateExpression(item, responseItem, answerExpression)
         item.extractAnswerOptions(data)
       }
       else ->

datacapture/src/test/java/com/google/android/fhir/datacapture/QuestionnaireViewModelTest.kt

@@ -4282,6 +4282,117 @@ class QuestionnaireViewModelTest {
       )
   }
 
+  @Test
+  fun `should return questionnaire item answer options for answer expression with fhirpath variable`() =
+    runTest {
+      val questionnaire =
+        Questionnaire().apply {
+          addItem(
+            QuestionnaireItemComponent().apply {
+              linkId = "a"
+              text = "Question 1"
+              type = Questionnaire.QuestionnaireItemType.CHOICE
+              repeats = true
+              initial =
+                listOf(
+                  Questionnaire.QuestionnaireItemInitialComponent(Coding("test", "1", "One")),
+                  Questionnaire.QuestionnaireItemInitialComponent(Coding("test", "2", "Two"))
+                )
+            }
+          )
+          addItem(
+            QuestionnaireItemComponent().apply {
+              linkId = "b"
+              text = "Question 2"
+              type = Questionnaire.QuestionnaireItemType.STRING
+              extension =
+                listOf(
+                  Extension(
+                    "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-answerExpression",
+                    Expression().apply {
+                      this.expression = "%resource.item[0].answer.value.select(%VAR1 + code)"
+                      this.language = Expression.ExpressionLanguage.TEXT_FHIRPATH.toCode()
+                    }
+                  ),
+                  Extension(
+                    "http://hl7.org/fhir/StructureDefinition/variable",
+                    Expression().apply {
+                      this.name = "VAR1"
+                      this.expression = "'Class '"
+                      this.language = Expression.ExpressionLanguage.TEXT_FHIRPATH.toCode()
+                    }
+                  )
+                )
+            }
+          )
+        }
+
+      state.set(EXTRA_QUESTIONNAIRE_JSON_STRING, printer.encodeResourceToString(questionnaire))
+      val viewModel = QuestionnaireViewModel(context, state)
+
+      viewModel.runViewModelBlocking {
+        val viewItem =
+          viewModel
+            .getQuestionnaireItemViewItemList()
+            .map { it.asQuestion() }
+            .single { it.questionnaireItem.linkId == "b" }
+        assertThat(viewItem.enabledAnswerOptions.map { it.valueStringType.value })
+          .containsExactly("Class 1", "Class 2")
+      }
+    }
+
+  @Test
+  fun `should return questionnaire item answer options for answer expression with fhirpath supplement context`() =
+    runTest {
+      val questionnaire =
+        Questionnaire().apply {
+          addItem(
+            QuestionnaireItemComponent().apply {
+              linkId = "a"
+              text = "Question 1"
+              type = Questionnaire.QuestionnaireItemType.CHOICE
+              repeats = true
+              initial =
+                listOf(
+                  Questionnaire.QuestionnaireItemInitialComponent(Coding("test", "1", "One")),
+                  Questionnaire.QuestionnaireItemInitialComponent(Coding("test", "2", "Two"))
+                )
+            }
+          )
+          addItem(
+            QuestionnaireItemComponent().apply {
+              linkId = "b"
+              text = "Question 2"
+              type = Questionnaire.QuestionnaireItemType.STRING
+              extension =
+                listOf(
+                  Extension(
+                    "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-answerExpression",
+                    Expression().apply {
+                      this.expression =
+                        "%resource.item[0].answer.value.select('Code ' + code + '-' + %context.linkId)"
+                      this.language = Expression.ExpressionLanguage.TEXT_FHIRPATH.toCode()
+                    }
+                  )
+                )
+            }
+          )
+        }
+
+      state.set(EXTRA_QUESTIONNAIRE_JSON_STRING, printer.encodeResourceToString(questionnaire))
+      val viewModel = QuestionnaireViewModel(context, state)
+
+      viewModel.runViewModelBlocking {
+        val viewItem =
+          viewModel
+            .getQuestionnaireItemViewItemList()
+            .map { it.asQuestion() }
+            .single { it.questionnaireItem.linkId == "b" }
+        assertThat(viewItem.enabledAnswerOptions.map { it.valueStringType.value })
+          .containsExactly("Code 1-b", "Code 2-b")
+      }
+    }
+
   // ==================================================================== //
   //                                                                      //
   //                 Answer Options Toggle Expression                     //