Allow setting optional fields on input objects to explicit null

Rakefile

@@ -25,6 +25,12 @@ task :generate do
         deserialize_expr: ->(expr) { "LocalDateTime.parse(jsonAsString(#{expr}, key))" },
         imports: ['java.time.LocalDateTime'],
       )
+    ],
+    custom_annotations: [
+      GraphQLJavaGen::Annotation.new(
+        'Nullable',
+        imports: ['com.shopify.graphql.support.Nullable']
+      ) { |field| !field.type.non_null? },
     ]
   ).save('support/src/test/java/com/shopify/graphql/support/Generated.java')
 

codegen/lib/graphql_java_gen.rb

@@ -253,10 +253,17 @@ def java_implements(type)
     "implements #{interfaces.to_a.join(', ')} "
   end
 
-  def java_annotations(field)
-    @annotations.map do |annotation|
+  def java_annotations(field, in_argument: false)
+    annotations = @annotations.map do |annotation|
       "@#{annotation.name}" if annotation.annotate?(field)
-    end.compact.join("\n")
+    end.compact
+    return "" unless annotations.any?
+
+    if in_argument
+      annotations.join(" ") + " "
+    else
+      annotations.join("\n")
+    end
   end
 
   def type_names_set

codegen/lib/graphql_java_gen/templates/APISchema.java.erb

@@ -237,7 +237,7 @@ public class <%= schema_name %> {
 
                 <% fields.each do |field| %>
                     <%= java_doc(field) %>
-                    <%= java_annotations(field) -%>
+                    <%= java_annotations(field) %>
                     public <%= java_output_type(field.type) %> get<%= field.classify_name %>() {
                       return (<%= java_output_type(field.type) %>) get("<%= field.name %>");
                     }
@@ -265,6 +265,7 @@ public class <%= schema_name %> {
                 <% end %>
                 <% type.optional_input_fields.each do |field| %>
                   private <%= java_input_type(field.type) %> <%= escape_reserved_word(field.camelize_name) %>;
+                  private boolean <%= field.camelize_name %>Seen = false;
                 <% end %>
 
                 <% unless type.required_input_fields.empty? %>
@@ -276,22 +277,25 @@ public class <%= schema_name %> {
                 <% end %>
 
                 <% type.required_input_fields.each do |field| %>
+                  <%= java_annotations(field) %>
                   public <%= java_input_type(field.type) %> get<%= field.classify_name %>() {
                       return <%= escape_reserved_word(field.camelize_name) %>;
                   }
 
-                  public <%= type.name %> set<%= field.classify_name %>(<%= java_input_type(field.type) %> <%= escape_reserved_word(field.camelize_name) %>) {
+                  public <%= type.name %> set<%= field.classify_name %>(<%= java_annotations(field, in_argument: true) %><%= java_input_type(field.type) %> <%= escape_reserved_word(field.camelize_name) %>) {
                       this.<%= escape_reserved_word(field.camelize_name) %> = <%= escape_reserved_word(field.camelize_name) %>;
                       return this;
                   }
                 <% end %>
                 <% type.optional_input_fields.each do |field| %>
+                  <%= java_annotations(field) %>
                   public <%= java_input_type(field.type) %> get<%= field.classify_name %>() {
                       return <%= escape_reserved_word(field.camelize_name) %>;
                   }
 
-                  public <%= type.name %> set<%= field.classify_name %>(<%= java_input_type(field.type) %> <%= escape_reserved_word(field.camelize_name) %>) {
+                  public <%= type.name %> set<%= field.classify_name %>(<%= java_annotations(field, in_argument: true) %><%= java_input_type(field.type) %> <%= escape_reserved_word(field.camelize_name) %>) {
                       this.<%= escape_reserved_word(field.camelize_name) %> = <%= escape_reserved_word(field.camelize_name) %>;
+                      this.<%= field.camelize_name %>Seen = true;
                       return this;
                   }
                 <% end %>
@@ -306,11 +310,15 @@ public class <%= schema_name %> {
                     <%= generate_build_input_code(escape_reserved_word(field.camelize_name), field.type) %>
                   <% end %>
                   <% type.optional_input_fields.each do |field| %>
-                    if (<%= escape_reserved_word(field.camelize_name) %> != null) {
+                    if (this.<%= field.camelize_name %>Seen) {
                       _queryBuilder.append(separator);
                       separator = ",";
                       _queryBuilder.append("<%= field.name %>:");
-                      <%= generate_build_input_code(escape_reserved_word(field.camelize_name), field.type) %>
+                      if (<%= escape_reserved_word(field.camelize_name) %> != null) {
+                        <%= generate_build_input_code(escape_reserved_word(field.camelize_name), field.type) %>
+                      } else {
+                        _queryBuilder.append("null");
+                      }
                     }
                   <% end %>
                   _queryBuilder.append('}');

codegen/test/support/schema.rb

@@ -91,6 +91,7 @@ module Schema
       argument :value, !types.Int
       argument :ttl, TimeType
       argument :negate, types.Boolean, default_value: false
+      argument :api_client, types.String
     end
 
     MutationType = GraphQL::ObjectType.define do

support/src/main/java/com/shopify/graphql/support/Nullable.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.shopify.graphql.support;
+
+import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PACKAGE;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Denotes that a parameter, field or method return value can be null.
+ * <p>
+ * When decorating a method call parameter, this denotes that the parameter can
+ * legitimately be null and the method will gracefully deal with it. Typically
+ * used on optional parameters.
+ * <p>
+ * When decorating a method, this denotes the method might legitimately return
+ * null.
+ * <p>
+ * This is a marker annotation and it has no specific attributes.
+ */
+@Documented
+@Retention(RUNTIME)
+@Target({METHOD, PARAMETER, FIELD, ANNOTATION_TYPE, PACKAGE})
+public @interface Nullable {
+}
+

support/src/test/java/com/shopify/graphql/support/AnnotationTest.java

@@ -0,0 +1,28 @@
+package com.shopify.graphql.support;
+
+import org.junit.Test;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Method;
+
+import static junit.framework.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import com.shopify.graphql.support.Generated;
+
+public class AnnotationTest {
+    @Test
+    public void testAppliesAnnotation() throws Exception {
+      Class<Generated> obj = Generated.class;
+      boolean foundNullable = false;
+      for (Class klass: obj.getDeclaredClasses()) {
+        for (Method method : klass.getDeclaredMethods()) {
+          if (method.isAnnotationPresent(Nullable.class)) {
+            foundNullable = true;
+            break;
+          }
+        }
+      }
+      assertTrue("Should have found a class with @Nullable annotation in Generated.java", foundNullable);
+    }
+}