EnableWhenExpression context literal fhirpath supplement implementation

catalog/src/main/assets/behavior_enable_when_expression.json

@@ -0,0 +1,75 @@
+{
+  "resourceType": "Questionnaire",
+  "item": [
+    {
+      "linkId": "1",
+      "type": "choice",
+      "text": "Has the client received this year's seasonal flu vaccine?",
+      "answerOption": [
+        {
+          "valueCoding": {
+            "code": "Y",
+            "display": "Yes",
+            "system": "custom"
+          }
+        },
+        {
+          "valueCoding": {
+            "code": "N",
+            "display": "No",
+            "system": "custom"
+          }
+        },
+        {
+          "valueCoding": {
+            "code": "unknown",
+            "display": "Unknown",
+            "system": "custom"
+          }
+        }
+      ]
+    },
+    {
+      "text": "Date of Vaccination?",
+      "type": "date",
+      "linkId": "yes",
+      "extension": [
+        {
+          "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression",
+          "valueExpression": {
+            "expression": "%resource.descendants().where(linkId='1').answer.value.display.lower() = %context.linkId",
+            "language": "text/fhirpath"
+          }
+        }
+      ]
+    },
+    {
+      "text": "Date of vaccination not provided",
+      "type": "display",
+      "linkId": "no",
+      "extension": [
+        {
+          "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression",
+          "valueExpression": {
+            "expression": "%resource.descendants().where(linkId='1').answer.value.display.lower() = %context.linkId",
+            "language": "text/fhirpath"
+          }
+        }
+      ]
+    },
+    {
+      "text": "Date of vaccination not known",
+      "type": "display",
+      "linkId": "unknown",
+      "extension": [
+        {
+          "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression",
+          "valueExpression": {
+            "expression": "%resource.descendants().where(linkId='1').answer.value.where(display.lower() = %context.linkId).exists()",
+            "language": "text/fhirpath"
+          }
+        }
+      ]
+    }
+  ]
+}

catalog/src/main/java/com/google/android/fhir/catalog/BehaviorListViewModel.kt

@@ -38,6 +38,11 @@ class BehaviorListViewModel(application: Application) : AndroidViewModel(applica
       R.string.behavior_name_calculated_expression,
       "behavior_calculated_expression.json"
     ),
+    ENABLE_WHEN_EXPRESSION(
+      R.drawable.ic_skiplogic_behavior,
+      R.string.behavior_name_enable_when_expression,
+      "behavior_enable_when_expression.json"
+    ),
     SKIP_LOGIC(
       R.drawable.ic_skiplogic_behavior,
       R.string.behavior_name_skip_logic,

catalog/src/main/res/values/strings.xml

@@ -43,6 +43,9 @@
     <string
         name="behavior_name_skip_logic_info"
     >If Yes is selected, a follow-up question is displayed. If No is selected, no follow-up questions are displayed.</string>
+    <string
+        name="behavior_name_enable_when_expression"
+    >Enable When Expression</string>
     <string
         name="behavior_name_calculated_expression_info"
     >Input age to automatically calculate birthdate until birthdate is updated manually.</string>

datacapture/src/main/java/com/google/android/fhir/datacapture/enablement/EnablementEvaluator.kt

@@ -19,7 +19,7 @@ package com.google.android.fhir.datacapture.enablement
 import com.google.android.fhir.compareTo
 import com.google.android.fhir.datacapture.extensions.allItems
 import com.google.android.fhir.datacapture.extensions.enableWhenExpression
-import com.google.android.fhir.datacapture.fhirpath.fhirPathEngine
+import com.google.android.fhir.datacapture.fhirpath.evaluateToBoolean
 import com.google.android.fhir.equals
 import org.hl7.fhir.r4.model.Questionnaire
 import org.hl7.fhir.r4.model.QuestionnaireResponse
@@ -110,8 +110,10 @@ internal class EnablementEvaluator(val questionnaireResponse: QuestionnaireRespo
 
     // Evaluate `enableWhenExpression`.
     if (enableWhenExpression != null && enableWhenExpression.hasExpression()) {
-      return fhirPathEngine.convertToBoolean(
-        fhirPathEngine.evaluate(questionnaireResponse, enableWhenExpression.expression)
+      return evaluateToBoolean(
+        questionnaireResponse,
+        questionnaireResponseItem,
+        enableWhenExpression.expression
       )
     }
 

datacapture/src/main/java/com/google/android/fhir/datacapture/fhirpath/FhirPathUtil.kt

@@ -19,6 +19,8 @@ package com.google.android.fhir.datacapture.fhirpath
 import ca.uhn.fhir.context.FhirContext
 import ca.uhn.fhir.context.FhirVersionEnum
 import org.hl7.fhir.r4.hapi.ctx.HapiWorkerContext
+import org.hl7.fhir.r4.model.QuestionnaireResponse
+import org.hl7.fhir.r4.model.QuestionnaireResponse.QuestionnaireResponseItemComponent
 import org.hl7.fhir.r4.model.Resource
 import org.hl7.fhir.r4.utils.FHIRPathEngine
 
@@ -34,3 +36,22 @@ internal val fhirPathEngine: FHIRPathEngine =
  */
 internal fun evaluateToDisplay(expressions: List<String>, data: Resource) =
   expressions.joinToString(" ") { fhirPathEngine.evaluateToString(data, it) }
+
+/**
+ * Evaluates the expression and returns the boolean result. The resources [QuestionnaireResponse]
+ * and [QuestionnaireResponseItemComponent] are passed as fhirPath supplements as defined in fhir
+ * specs https://build.fhir.org/ig/HL7/sdc/expressions.html#fhirpath-supplements
+ *
+ * %resource = [QuestionnaireResponse], %context = [QuestionnaireResponseItemComponent]
+ */
+internal fun evaluateToBoolean(
+  questionnaireResponse: QuestionnaireResponse,
+  questionnaireResponseItemComponent: QuestionnaireResponseItemComponent,
+  expression: String
+) =
+  fhirPathEngine.evaluateToBoolean(
+    questionnaireResponse,
+    null,
+    questionnaireResponseItemComponent,
+    expression
+  )

datacapture/src/test/java/com/google/android/fhir/datacapture/enablement/EnablementEvaluatorTest.kt

@@ -38,6 +38,8 @@ import org.robolectric.annotation.Config
 @RunWith(RobolectricTestRunner::class)
 @Config(sdk = [Build.VERSION_CODES.P])
 class EnablementEvaluatorTest {
+  val iParser: IParser = FhirContext.forR4Cached().newJsonParser()
+
   @Test
   fun evaluate_noEnableWhen_shouldReturnTrue() {
     assertEnableWhen().isTrue()
@@ -159,8 +161,6 @@ class EnablementEvaluatorTest {
       } 
       """.trimIndent()
 
-    val iParser: IParser = FhirContext.forR4().newJsonParser()
-
     val questionnaire =
       iParser.parseResource(Questionnaire::class.java, questionnaireJson) as Questionnaire
 
@@ -241,8 +241,6 @@ class EnablementEvaluatorTest {
       } 
       """.trimIndent()
 
-    val iParser: IParser = FhirContext.forR4().newJsonParser()
-
     val questionnaire =
       iParser.parseResource(Questionnaire::class.java, questionnaireJson) as Questionnaire
 
@@ -263,6 +261,85 @@ class EnablementEvaluatorTest {
       .isFalse()
   }
 
+  @Test
+  fun `evaluate() should evaluate enableWhenExpression with context fhirpath supplement literal`() =
+    runBlocking {
+      @Language("JSON")
+      val questionnaireJson =
+        """
+    {
+      "resourceType": "Questionnaire",
+          "item": [
+            {
+              "linkId": "1",
+              "definition": "http://hl7.org/fhir/StructureDefinition/Patient#Patient.gender",
+              "type": "choice",
+              "text": "Gender"
+            },
+            {
+              "extension": [
+                {
+                  "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression",
+                  "valueExpression": {
+                    "language": "text/fhirpath",
+                    "expression": "%resource.repeat(item).where(linkId='1').answer.value.code = %context.linkId"
+                  }
+                }
+              ],
+              "linkId" : "female",
+              "text": "Have you had mammogram before?(enableWhenExpression = only when gender is female)",
+              "type": "choice",
+              "answerValueSet": "http://hl7.org/fhir/ValueSet/yesnodontknow"
+            }
+          ]
+    }
+        """.trimIndent()
+
+      @Language("JSON")
+      val questionnaireResponseJson =
+        """
+    {
+      "resourceType": "QuestionnaireResponse",
+      "item": [
+        {
+          "linkId": "1",
+          "answer": [
+            {
+              "valueCoding": {
+                "system": "http://hl7.org/fhir/administrative-gender",
+                "code": "female",
+                "display": "Female"
+              }
+            }
+          ]
+        },
+        {
+          "linkId": "female"
+        }
+      ]
+    } 
+        """.trimIndent()
+
+      val questionnaire =
+        iParser.parseResource(Questionnaire::class.java, questionnaireJson) as Questionnaire
+
+      val questionnaireItem: Questionnaire.QuestionnaireItemComponent =
+        questionnaire.item.find { it.linkId == "female" }!!
+
+      val questionnaireResponse =
+        iParser.parseResource(QuestionnaireResponse::class.java, questionnaireResponseJson)
+          as QuestionnaireResponse
+
+      assertThat(
+          EnablementEvaluator(questionnaireResponse)
+            .evaluate(
+              questionnaireItem,
+              questionnaireResponse.item[1],
+            )
+        )
+        .isTrue()
+    }
+
   @Test
   fun evaluate_expectAnswerDoesNotExist_answerDoesNotExist_shouldReturnTrue() {
     assertEnableWhen(