Remove Engine dependency from SDC.

datacapture/build.gradle.kts

@@ -70,8 +70,6 @@ dependencies {
 
   coreLibraryDesugaring(Dependencies.desugarJdkLibs)
 
-  debugImplementation(project(":engine"))
-
   implementation(Dependencies.androidFhirCommon)
   implementation(Dependencies.Androidx.appCompat)
   implementation(Dependencies.Androidx.constraintLayout)

datacapture/src/main/java/com/google/android/fhir/datacapture/DataCaptureConfig.kt

@@ -20,6 +20,7 @@ import android.app.Application
 import com.google.android.fhir.datacapture.DataCaptureConfig.Provider
 import org.hl7.fhir.r4.context.SimpleWorkerContext
 import org.hl7.fhir.r4.model.Coding
+import org.hl7.fhir.r4.model.Resource
 import org.hl7.fhir.r4.model.StructureMap
 import org.hl7.fhir.utilities.npm.NpmPackage
 
@@ -45,7 +46,10 @@ data class DataCaptureConfig(
    * should try to include the smallest [NpmPackage] possible that contains only the resources
    * needed by [StructureMap]s used by the client app.
    */
-  var npmPackage: NpmPackage? = null
+  var npmPackage: NpmPackage? = null,
+
+  /** A [XFhirQueryResolver] may be set by the client to resolve xFhir queries for the library.*/
+  var xFhirQueryResolver: XFhirQueryResolver? = null
 ) {
 
   internal val simpleWorkerContext: SimpleWorkerContext by lazy {
@@ -75,3 +79,14 @@ data class DataCaptureConfig(
 interface ExternalAnswerValueSetResolver {
   suspend fun resolve(uri: String): List<Coding>
 }
+
+/**
+ * Resolves resources based on the provided xFhir query. This allows the library to resolve
+ * x-fhir-query answer expressions.
+ *
+ * NOTE: The result of the resolution may be cached to improve performance. In other words, the
+ * resolver may be called only once after which the Resources may be used multiple times in the UI.
+ */
+fun interface XFhirQueryResolver {
+  suspend fun resolve(xFhirQuery: String): List<Resource>
+}

datacapture/src/main/java/com/google/android/fhir/datacapture/MoreQuestionnaireItemComponents.kt

@@ -21,7 +21,6 @@ import androidx.core.text.HtmlCompat
 import com.google.android.fhir.datacapture.common.datatype.asStringValue
 import com.google.android.fhir.datacapture.utilities.evaluateToDisplay
 import com.google.android.fhir.getLocalizedText
-import com.google.android.fhir.logicalId
 import org.hl7.fhir.r4.model.Base
 import org.hl7.fhir.r4.model.BooleanType
 import org.hl7.fhir.r4.model.CodeType
@@ -545,3 +544,8 @@ fun List<Questionnaire.QuestionnaireItemComponent>.flattened():
  */
 fun Questionnaire.QuestionnaireItemComponent.getNestedQuestionnaireResponseItems() =
   item.map { it.createQuestionnaireResponseItem() }
+
+val Resource.logicalId: String
+  get() {
+    return this.idElement?.idPart.orEmpty()
+  }

datacapture/src/main/java/com/google/android/fhir/datacapture/QuestionnaireViewModel.kt

@@ -25,7 +25,6 @@ import androidx.lifecycle.viewModelScope
 import ca.uhn.fhir.context.FhirContext
 import ca.uhn.fhir.context.FhirVersionEnum
 import ca.uhn.fhir.parser.IParser
-import com.google.android.fhir.FhirEngineProvider
 import com.google.android.fhir.datacapture.enablement.EnablementEvaluator
 import com.google.android.fhir.datacapture.fhirpath.ExpressionEvaluator.detectExpressionCyclicDependency
 import com.google.android.fhir.datacapture.fhirpath.ExpressionEvaluator.evaluateCalculatedExpressions
@@ -38,7 +37,6 @@ import com.google.android.fhir.datacapture.validation.QuestionnaireResponseValid
 import com.google.android.fhir.datacapture.validation.Valid
 import com.google.android.fhir.datacapture.validation.ValidationResult
 import com.google.android.fhir.datacapture.views.QuestionnaireItemViewItem
-import com.google.android.fhir.search.search
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
@@ -57,7 +55,9 @@ internal class QuestionnaireViewModel(application: Application, state: SavedStat
   AndroidViewModel(application) {
 
   private val parser: IParser by lazy { FhirContext.forCached(FhirVersionEnum.R4).newJsonParser() }
-  private val fhirEngine by lazy { FhirEngineProvider.getInstance(application) }
+  private val xFhirQueryResolver: XFhirQueryResolver? by lazy {
+    DataCapture.getConfiguration(application).xFhirQueryResolver
+  }
 
   /** The current questionnaire as questions are being answered. */
   internal val questionnaire: Questionnaire
@@ -499,13 +499,18 @@ internal class QuestionnaireViewModel(application: Application, state: SavedStat
     expression: Expression,
   ): List<Questionnaire.QuestionnaireItemAnswerOptionComponent> {
     val data =
-      if (expression.isXFhirQuery) fhirEngine.search(expression.expression)
-      else if (expression.isFhirPath)
+      if (expression.isXFhirQuery) {
+        checkNotNull(xFhirQueryResolver) {
+          "XFhirQueryResolver cannot be null. Please provide the XFhirQueryResolver via DataCaptureConfig"
+        }
+        xFhirQueryResolver!!.resolve(expression.expression)
+      } else if (expression.isFhirPath) {
         fhirPathEngine.evaluate(questionnaireResponse, expression.expression)
-      else
+      } else {
         throw UnsupportedOperationException(
           "${expression.language} not supported for answer-expression yet"
         )
+      }
 
     return item.extractAnswerOptions(data)
   }

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

@@ -2894,13 +2894,13 @@ class QuestionnaireViewModelTest {
   fun `resolveAnswerExpression() should return questionnaire item answer options for answer expression and choice column`() =
     runBlocking {
       val practitioner =
-        Practitioner()
-          .apply {
-            id = UUID.randomUUID().toString()
-            active = true
-            addName(HumanName().apply { this.family = "John" })
-          }
-          .also { fhirEngine.create(it) }
+        Practitioner().apply {
+          id = UUID.randomUUID().toString()
+          active = true
+          addName(HumanName().apply { this.family = "John" })
+        }
+      ApplicationProvider.getApplicationContext<DataCaptureTestApplication>()
+        .dataCaptureConfiguration = DataCaptureConfig(xFhirQueryResolver = { listOf(practitioner) })
 
       val questionnaire =
         Questionnaire().apply {
@@ -2939,6 +2939,47 @@ class QuestionnaireViewModelTest {
         .isEqualTo("Practitioner/${practitioner.logicalId}")
     }
 
+  @Test
+  fun `resolveAnswerExpression() should throw exception when XFhirQueryResolver is not provided`() {
+    val questionnaire =
+      Questionnaire().apply {
+        addItem(
+          Questionnaire.QuestionnaireItemComponent().apply {
+            linkId = "a"
+            text = "answer expression question text"
+            type = Questionnaire.QuestionnaireItemType.REFERENCE
+            extension =
+              listOf(
+                Extension(
+                  "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-answerExpression",
+                  Expression().apply {
+                    this.expression = "Practitioner?active=true"
+                    this.language = Expression.ExpressionLanguage.APPLICATION_XFHIRQUERY.toCode()
+                  }
+                ),
+                Extension(
+                    "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-choiceColumn"
+                  )
+                  .apply {
+                    this.addExtension(Extension("path", StringType("id")))
+                    this.addExtension(Extension("label", StringType("name")))
+                    this.addExtension(Extension("forDisplay", BooleanType(true)))
+                  }
+              )
+          }
+        )
+      }
+    state.set(EXTRA_QUESTIONNAIRE_JSON_STRING, printer.encodeResourceToString(questionnaire))
+    val viewModel = QuestionnaireViewModel(context, state)
+    val exception =
+      Assert.assertThrows(null, IllegalStateException::class.java) {
+        runBlocking { viewModel.resolveAnswerExpression(questionnaire.itemFirstRep) }
+      }
+    assertThat(exception.message)
+      .isEqualTo(
+        "XFhirQueryResolver cannot be null. Please provide the XFhirQueryResolver via DataCaptureConfig"
+      )
+  }
   // Test cases for submit button
 
   @Test