Subscription Lookup Should Use Alias if Specified

server/servers/api/src/main/scala/com/prisma/subscriptions/SubscriptionExecutor.scala

@@ -11,8 +11,9 @@ import com.prisma.shared.models.ModelMutationType.ModelMutationType
 import com.prisma.shared.models._
 import com.prisma.subscriptions.schema.{QueryTransformer, SubscriptionSchema, VariablesTransformer}
 import play.api.libs.json._
-import sangria.ast.Document
+import sangria.ast.{Document, Selection}
 import sangria.execution.Executor
+import sangria.marshalling.queryAst
 import sangria.parser.QueryParser
 import sangria.renderer.QueryRenderer
 
@@ -112,8 +113,22 @@ object SubscriptionExecutor {
           deferredResolver = new DeferredResolverImpl(dataResolver)
         )
         .map { result =>
-          val lookup = result.as[JsObject] \ "data" \ camelCase(model.name)
-          if (lookup.validate[JsValue].get != JsNull) Some(result) else None
+          val lookup = for {
+            subscriptionOperation <- transformedQuery.operations.find(x => x._2.operationType == sangria.ast.OperationType.Subscription)
+            fields                = subscriptionOperation._2.selections.collect { case x: sangria.ast.Field => x }
+            field                 <- fields.find(p => p.name == camelCase(model.name))
+          } yield {
+            field.alias match {
+              case Some(alias) => result.as[JsObject] \ "data" \ alias
+              case None        => result.as[JsObject] \ "data" \ camelCase(model.name)
+            }
+          }
+
+          lookup match {
+            case None       => None
+            case Some(look) => if (look.validate[JsValue].get != JsNull) Some(result) else None
+          }
+
         }
     } else {
       Future.successful(None)

server/servers/subscriptions/src/test/scala/com/prisma/subscriptions/specs/SubscriptionFilterSpec.scala

@@ -104,6 +104,48 @@ class SubscriptionFilterSpec extends FlatSpec with Matchers with SubscriptionSpe
     }
   }
 
+  "this" should "work when using aliases" in {
+    testInitializedWebsocket(project) { wsClient =>
+      wsClient.sendMessage(
+        startMessage(
+          id = "3",
+          query = """subscription {
+                    |  alias: todo{
+                    |    mutation
+                    |    previousValues {
+                    |      id
+                    |      text
+                    |      status
+                    |    }
+                    |  }
+                    |}""".stripMargin
+        )
+      )
+
+      sleep(8000)
+
+      val event = nodeEvent(
+        modelId = model.name,
+        changedFields = Seq("text"),
+        previousValues = s"""{"id":"$testNodeId", "text":"event1", "status": "Active", "tags":[]}"""
+      )
+
+      sssEventsTestKit.publish(Only(s"subscription:event:${project.id}:updateTodo"), event)
+
+      wsClient.expectMessage(
+        dataMessage(
+          id = "3",
+          payload = s"""{
+                       |  "alias":{
+                       |    "mutation":"UPDATED",
+                       |    "previousValues":{"id":"$testNodeId", "text":"event1", "status":"Active"}
+                       |  }
+                       |}""".stripMargin
+        )
+      )
+    }
+  }
+
   "this" should "support scalar lists in previous values" ignore {
     testInitializedWebsocket(project) { wsClient =>
       wsClient.sendMessage(