Refetch transit leg with a leg query of GTFS GraphQL API

src/main/java/org/opentripplanner/apis/gtfs/datafetchers/LegImpl.java

@@ -1,5 +1,6 @@
 package org.opentripplanner.apis.gtfs.datafetchers;
 
+import graphql.relay.Relay;
 import graphql.schema.DataFetcher;
 import graphql.schema.DataFetchingEnvironment;
 import java.util.List;
@@ -23,6 +24,7 @@
 import org.opentripplanner.model.plan.StreetLeg;
 import org.opentripplanner.model.plan.TransitLeg;
 import org.opentripplanner.model.plan.WalkStep;
+import org.opentripplanner.model.plan.legreference.LegReferenceSerializer;
 import org.opentripplanner.routing.alertpatch.TransitAlert;
 import org.opentripplanner.routing.alternativelegs.AlternativeLegs;
 import org.opentripplanner.routing.alternativelegs.AlternativeLegsFilter;
@@ -324,4 +326,13 @@ public DataFetcher<Iterable<Leg>> nextLegs() {
   public DataFetcher<Double> accessibilityScore() {
     return environment -> NumberMapper.toDouble(getSource(environment).accessibilityScore());
   }
+
+  @Override
+  public DataFetcher<Relay.ResolvedGlobalId> id() {
+    return environment -> {
+      var ref = getSource(environment).getLegReference();
+      var id = LegReferenceSerializer.encode(ref);
+      return new Relay.ResolvedGlobalId("Leg", id);
+    };
+  }
 }

src/main/java/org/opentripplanner/apis/gtfs/datafetchers/NodeTypeResolver.java

@@ -8,6 +8,7 @@
 import graphql.schema.TypeResolver;
 import org.opentripplanner.ext.fares.model.FareRuleSet;
 import org.opentripplanner.model.TripTimeOnDate;
+import org.opentripplanner.model.plan.Leg;
 import org.opentripplanner.routing.alertpatch.TransitAlert;
 import org.opentripplanner.routing.graphfinder.NearbyStop;
 import org.opentripplanner.routing.graphfinder.PatternAtStop;
@@ -85,6 +86,9 @@ public GraphQLObjectType getType(TypeResolutionEnvironment environment) {
     if (o instanceof Trip) {
       return schema.getObjectType("Trip");
     }
+    if (o instanceof Leg) {
+      return schema.getObjectType("Leg");
+    }
     return null;
   }
 

src/main/java/org/opentripplanner/apis/gtfs/datafetchers/QueryTypeImpl.java

@@ -42,6 +42,8 @@
 import org.opentripplanner.graph_builder.issue.api.DataImportIssueStore;
 import org.opentripplanner.gtfs.mapping.DirectionMapper;
 import org.opentripplanner.model.TripTimeOnDate;
+import org.opentripplanner.model.plan.legreference.LegReference;
+import org.opentripplanner.model.plan.legreference.LegReferenceSerializer;
 import org.opentripplanner.routing.alertpatch.EntitySelector;
 import org.opentripplanner.routing.alertpatch.TransitAlert;
 import org.opentripplanner.routing.api.request.RouteRequest;
@@ -445,6 +447,12 @@ public DataFetcher<Object> node() {
             // TODO: Add geometry
             return new NearbyStop(stop, Integer.parseInt(parts[0]), null, null);
           }
+        case "Leg":
+          LegReference ref = LegReferenceSerializer.decode(id);
+          if (ref == null) {
+            return null;
+          }
+          return ref.getLeg(transitService);
         case "TicketType":
           return null; //TODO
         case "Trip":

src/main/java/org/opentripplanner/apis/gtfs/generated/GraphQLDataFetchers.java

@@ -482,6 +482,8 @@ public interface GraphQLLeg {
 
     public DataFetcher<String> headsign();
 
+    public DataFetcher<graphql.relay.Relay.ResolvedGlobalId> id();
+
     public DataFetcher<Boolean> interlineWithPreviousLeg();
 
     public DataFetcher<Boolean> intermediatePlace();

src/main/java/org/opentripplanner/apis/transmodel/TransmodelGraphQLSchema.java

@@ -1596,7 +1596,7 @@ private GraphQLSchema create() {
         GraphQLFieldDefinition
           .newFieldDefinition()
           .name("leg")
-          .description("Refetch a single leg based on its id")
+          .description("Refetch a single transit leg based on its id")
           .withDirective(gqlUtil.timingData)
           .type(LegType.REF)
           .argument(

src/main/java/org/opentripplanner/apis/transmodel/model/plan/LegType.java

@@ -63,7 +63,9 @@ public static GraphQLObjectType create(
         GraphQLFieldDefinition
           .newFieldDefinition()
           .name("id")
-          .description("An identifier for the leg, which can be used to re-fetch the information.")
+          .description(
+            "An identifier for the leg, which can be used to re-fetch transit leg information."
+          )
           .type(Scalars.GraphQLID)
           .dataFetcher(env -> LegReferenceSerializer.encode(leg(env).getLegReference()))
           .build()

src/main/java/org/opentripplanner/model/plan/legreference/LegReferenceSerializer.java

@@ -18,6 +18,8 @@
  */
 public class LegReferenceSerializer {
 
+  public static final String notAvailable = "NotAvailable";
+
   private static final Logger LOG = LoggerFactory.getLogger(LegReferenceSerializer.class);
 
   /** private constructor to prevent instantiating this utility class */
@@ -26,7 +28,7 @@ private LegReferenceSerializer() {}
   @Nullable
   public static String encode(LegReference legReference) {
     if (legReference == null) {
-      return null;
+      return notAvailable;
     }
     LegReferenceType typeEnum = LegReferenceType
       .forClass(legReference.getClass())
@@ -47,7 +49,7 @@ public static String encode(LegReference legReference) {
 
   @Nullable
   public static LegReference decode(String legReference) {
-    if (legReference == null) {
+    if (legReference.equals(notAvailable)) {
       return null;
     }
 

src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls

@@ -611,7 +611,7 @@ type Itinerary {
   walkTime: Long
 }
 
-type Leg {
+type Leg implements Node {
   """
   Computes a numeric accessibility score between 0 and 1.
 
@@ -670,6 +670,12 @@ type Leg {
   """
   headsign: String
   """
+  An identifier for the leg, which can be used to re-fetch transit leg information.
+  Re-fetching fails when the underlying transit data no longer exists.
+  Non-transit legs cannot be refetched using their id.
+  """
+  id: ID!
+  """
   Interlines with previous leg.
   This is true when the same vehicle is used for the previous leg as for this leg
   and passenger can stay inside the vehicle.

src/main/resources/org/opentripplanner/apis/transmodel/schema.graphql

@@ -325,7 +325,7 @@ type Leg {
   fromPlace: Place!
   "Generalized cost or weight of the leg. Used for debugging."
   generalizedCost: Int
-  "An identifier for the leg, which can be used to re-fetch the information."
+  "An identifier for the leg, which can be used to re-fetch transit leg information."
   id: ID
   interchangeFrom: Interchange
   interchangeTo: Interchange
@@ -647,7 +647,7 @@ type QueryType {
   groupOfLines(id: String!): GroupOfLines
   "Get all groups of lines"
   groupsOfLines: [GroupOfLines!]!
-  "Refetch a single leg based on its id"
+  "Refetch a single transit leg based on its id"
   leg(id: ID!): Leg @timingData
   "Get a single line based on its id"
   line(id: ID!): Line @timingData

src/test/java/org/opentripplanner/model/plan/legreference/LegReferenceSerializerTest.java

@@ -89,8 +89,8 @@ void testScheduledTransitLegReferenceLegacyV2Deserialize() {
   }
 
   @Test
-  void testNullSerializedLegReference() {
-    assertNull(LegReferenceSerializer.decode(null));
+  void testUnresolvedSerializedLegReference() {
+    assertNull(LegReferenceSerializer.decode(LegReferenceSerializer.notAvailable));
   }
 
   @Test

src/test/resources/org/opentripplanner/apis/gtfs/expectations/plan-extended.json

@@ -64,7 +64,8 @@
               "intermediatePlaces" : null,
               "alerts" : [ ],
               "rideHailingEstimate" : null,
-              "accessibilityScore" : null
+              "accessibilityScore" : null,
+              "id" : "TGVnOk5vdEF2YWlsYWJsZQ"
             },
             {
               "mode" : "BUS",
@@ -154,7 +155,8 @@
               ],
               "alerts" : [ ],
               "rideHailingEstimate" : null,
-              "accessibilityScore" : null
+              "accessibilityScore" : null,
+              "id": "TGVnOnJPMEFCWGRCQUJoVFEwaEZSRlZNUlVSZlZGSkJUbE5KVkY5TVJVZGZWak1BQlVZNk1USXlBQW95TURJd0xUQXlMVEF5QUFBQUJRQUFBQWNBQTBZNlFnQURSanBEQUFBPQ"
             },
             {
               "mode" : "RAIL",
@@ -264,7 +266,8 @@
                 }
               ],
               "rideHailingEstimate" : null,
-              "accessibilityScore" : null
+              "accessibilityScore" : null,
+              "id": "TGVnOnJPMEFCWGRCQUJoVFEwaEZSRlZNUlVSZlZGSkJUbE5KVkY5TVJVZGZWak1BQlVZNk5ETTVBQW95TURJd0xUQXlMVEF5QUFBQUJRQUFBQWNBQTBZNlF3QURSanBFQUFBPQ"
             },
             {
               "mode" : "CAR",
@@ -334,11 +337,12 @@
                 },
                 "arrival" : "PT10M"
               },
-              "accessibilityScore" : null
+              "accessibilityScore" : null,
+              "id": "TGVnOk5vdEF2YWlsYWJsZQ"
             }
           ]
         }
       ]
     }
   }
-}
+}

src/test/resources/org/opentripplanner/apis/gtfs/queries/plan-extended.graphql

@@ -151,6 +151,7 @@
           arrival
         }
         accessibilityScore
+        id
       }
     }
   }