fix: associated Flutter models can sync to cloud (#988)

Version 1.6.3 of Amplify fixed an issue where associated/connected
models failed to sync down from AppSync, when being used with
Flutter-style ModelSchema.

Unfortunately, 1.6.3 stopped short of supporting associated models when
syncing *up* to AppSync, from the client.

This current change expands the HybridCloudSyncInstrumentationTest, to
demonstrate successful sync up and down from AppSync.

To support this, request-forming logic is extracted from the
ModelSchema, and split accross the AppSyncRequestFactory (for DataStore)
and the AppSyncGraphQLRequestFactory (for API category). The DataStore
flavor of the factory is expanded to properly build requests when
dealing with associations in Flutter-style SerializedModels.

Author: jamesonwilliams

aws-api/src/main/java/com/amplifyframework/api/aws/AppSyncGraphQLRequestFactory.java

@@ -15,13 +15,19 @@
 
 package com.amplifyframework.api.aws;
 
+import androidx.annotation.NonNull;
+
 import com.amplifyframework.AmplifyException;
 import com.amplifyframework.api.graphql.GraphQLRequest;
 import com.amplifyframework.api.graphql.MutationType;
 import com.amplifyframework.api.graphql.PaginatedResult;
 import com.amplifyframework.api.graphql.QueryType;
 import com.amplifyframework.api.graphql.SubscriptionType;
+import com.amplifyframework.core.model.AuthRule;
+import com.amplifyframework.core.model.AuthStrategy;
 import com.amplifyframework.core.model.Model;
+import com.amplifyframework.core.model.ModelAssociation;
+import com.amplifyframework.core.model.ModelField;
 import com.amplifyframework.core.model.ModelSchema;
 import com.amplifyframework.core.model.query.predicate.BeginsWithQueryOperator;
 import com.amplifyframework.core.model.query.predicate.BetweenQueryOperator;
@@ -40,13 +46,16 @@
 import com.amplifyframework.util.Casing;
 import com.amplifyframework.util.TypeMaker;
 
+import java.lang.reflect.Field;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
 
 /**
  * Converts provided model or class type into a request container
@@ -198,7 +207,7 @@ public static <R, T extends Model> GraphQLRequest<R> buildMutation(
             if (MutationType.DELETE.equals(type)) {
                 builder.variable("input", inputType, Collections.singletonMap("id", model.getId()));
             } else {
-                builder.variable("input", inputType, schema.getMapOfFieldNameAndValues(model));
+                builder.variable("input", inputType, getMapOfFieldNameAndValues(schema, model));
             }
 
             if (!QueryPredicates.all().equals(predicate)) {
@@ -339,4 +348,52 @@ private static Object appSyncOpValue(QueryOperator<?> qOp) {
                 );
         }
     }
+
+    private static Map<String, Object> getMapOfFieldNameAndValues(
+            @NonNull ModelSchema schema, @NonNull Model instance) throws AmplifyException {
+        if (!instance.getClass().getSimpleName().equals(schema.getName())) {
+            throw new AmplifyException(
+                "The object provided is not an instance of " + schema.getName() + ".",
+                "Please provide an instance of " + schema.getName() + " that matches the schema type."
+            );
+        }
+        final Map<String, Object> result = new HashMap<>();
+        for (ModelField modelField : schema.getFields().values()) {
+            String fieldName = modelField.getName();
+            try {
+                Field privateField = instance.getClass().getDeclaredField(modelField.getName());
+                privateField.setAccessible(true);
+                Object fieldValue = privateField.get(instance);
+                final ModelAssociation association = schema.getAssociations().get(fieldName);
+                if (association == null) {
+                    result.put(fieldName, fieldValue);
+                } else if (association.isOwner()) {
+                    Model target = (Model) Objects.requireNonNull(fieldValue);
+                    result.put(association.getTargetName(), target.getId());
+                }
+                // Ignore if field is associated, but is not a "belongsTo" relationship
+            } catch (Exception exception) {
+                throw new AmplifyException(
+                    "An invalid field was provided. " + fieldName + " is not present in " + schema.getName(),
+                    exception,
+                    "Check if this model schema is a correct representation of the fields in the provided Object");
+            }
+        }
+
+        /*
+         * If the owner field exists on the model, and the value is null, it should be omitted when performing a
+         * mutation because the AppSync server will automatically populate it using the authentication token provided
+         * in the request header.  The logic below filters out the owner field if null for this scenario.
+         */
+        for (AuthRule authRule : schema.getAuthRules()) {
+            if (AuthStrategy.OWNER.equals(authRule.getAuthStrategy())) {
+                String ownerField = authRule.getOwnerFieldOrDefault();
+                if (result.containsKey(ownerField) && result.get(ownerField) == null) {
+                    result.remove(ownerField);
+                }
+            }
+        }
+
+        return result;
+    }
 }

aws-api/src/test/java/com/amplifyframework/api/aws/AppSyncGraphQLRequestFactoryTest.java

@@ -15,9 +15,15 @@
 
 package com.amplifyframework.api.aws;
 
+import androidx.annotation.NonNull;
+
 import com.amplifyframework.api.graphql.GraphQLRequest;
 import com.amplifyframework.api.graphql.MutationType;
 import com.amplifyframework.api.graphql.SubscriptionType;
+import com.amplifyframework.core.model.AuthStrategy;
+import com.amplifyframework.core.model.Model;
+import com.amplifyframework.core.model.annotations.AuthRule;
+import com.amplifyframework.core.model.annotations.ModelConfig;
 import com.amplifyframework.core.model.query.predicate.QueryPredicates;
 import com.amplifyframework.core.model.temporal.Temporal;
 import com.amplifyframework.testmodels.meeting.Meeting;
@@ -32,8 +38,12 @@
 import org.skyscreamer.jsonassert.JSONAssert;
 
 import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
+import static org.junit.Assert.assertEquals;
+
 /**
  * Tests the {@link AppSyncGraphQLRequestFactory}.
  */
@@ -156,4 +166,74 @@ public void validateDateSerializer() throws JSONException {
         JSONAssert.assertEquals(Resources.readAsString("create-meeting1.txt"),
                 requestToCreateMeeting1.getContent(), true);
     }
+
+    /**
+     * Verify that the owner field is removed if the value is null.
+     */
+    @Test
+    public void ownerFieldIsRemovedIfNull() {
+        // Expect
+        Map<String, Object> expected = new HashMap<>();
+        expected.put("id", "111");
+        expected.put("description", "Mop the floor");
+
+        // Act
+        Todo todo = new Todo("111", "Mop the floor", null);
+        @SuppressWarnings("unchecked")
+        Map<String, Object> actual = (Map<String, Object>)
+            AppSyncGraphQLRequestFactory.buildMutation(todo, QueryPredicates.all(), MutationType.CREATE)
+                .getVariables()
+                .get("input");
+
+        // Assert
+        assertEquals(expected, actual);
+    }
+
+    /**
+     * Verify that the owner field is NOT removed if the value is set..
+     */
+    @Test
+    public void ownerFieldIsNotRemovedIfSet() {
+        // Expect
+        Map<String, Object> expected = new HashMap<>();
+        expected.put("id", "111");
+        expected.put("description", "Mop the floor");
+        expected.put("owner", "johndoe");
+
+        // Act
+        Todo todo = new Todo("111", "Mop the floor", "johndoe");
+        @SuppressWarnings("unchecked")
+        Map<String, Object> actual = (Map<String, Object>)
+            AppSyncGraphQLRequestFactory.buildMutation(todo, QueryPredicates.all(), MutationType.CREATE)
+                .getVariables()
+                .get("input");
+
+        // Assert
+        assertEquals(expected, actual);
+    }
+
+    @ModelConfig(authRules = { @AuthRule(allow = AuthStrategy.OWNER) })
+    static final class Todo implements Model {
+        @com.amplifyframework.core.model.annotations.ModelField(targetType = "ID", isRequired = true)
+        private final String id;
+
+        @com.amplifyframework.core.model.annotations.ModelField(isRequired = true)
+        private final String description;
+
+        @com.amplifyframework.core.model.annotations.ModelField
+        private final String owner;
+
+        @SuppressWarnings("ParameterName") // checkstyle wants variable names to be >2 chars, but id is only 2.
+        Todo(String id, String description, String owner) {
+            this.id = id;
+            this.description = description;
+            this.owner = owner;
+        }
+
+        @NonNull
+        @Override
+        public String getId() {
+            return "111";
+        }
+    }
 }