Add integration test

Author: martinbonnin

src/main/java/graphql/execution/NonNullableFieldValidator.java

@@ -34,7 +34,7 @@ public NonNullableFieldValidator(ExecutionContext executionContext, ExecutionSte
      */
     public <T> T validate(ExecutionStrategyParameters parameters, T result) throws NonNullableFieldWasNullException {
         if (result == null) {
-            if (executionStepInfo.isNonNullType() && executionContext.propagateErrors()) {
+            if (executionStepInfo.isNonNullType()) {
                 // see https://spec.graphql.org/October2021/#sec-Errors-and-Non-Nullability
                 //
                 //    > If the field returns null because of an error which has already been added to the "errors" list in the response,
@@ -56,7 +56,9 @@ public <T> T validate(ExecutionStrategyParameters parameters, T result) throws N
                 } else {
                     executionContext.addError(error, path);
                 }
-                throw nonNullException;
+                if (executionContext.propagateErrors()) {
+                    throw nonNullException;
+                }
             }
         }
         return result;

src/test/groovy/graphql/execution/NoErrorPropagationTest.groovy

@@ -0,0 +1,41 @@
+package graphql.execution
+
+import graphql.ExecutionInput
+import graphql.TestUtil
+import graphql.schema.idl.RuntimeWiring
+import graphql.schema.idl.SchemaGenerator
+import graphql.GraphQL
+import spock.lang.Specification
+
+class NoErrorPropagationTest extends Specification {
+
+    def "when error propagation is disabled null is returned"() {
+
+        def sdl = '''
+            type Query {
+                foo : Int! 
+            }
+        '''
+
+        def options = SchemaGenerator.Options.defaultOptions().addOnErrorDirective(true)
+
+        def schema = TestUtil.schema(options, sdl, RuntimeWiring.MOCKED_WIRING)
+        def graphql = GraphQL.newGraphQL(schema).build()
+
+        def query = '''
+            query GetFoo @errorHandling(onError: NULL) { foo }
+        '''
+        when:
+
+        ExecutionInput ei = ExecutionInput.newExecutionInput(query).root(
+                [foo: null]
+        ).build()
+
+        def er = graphql.execute(ei)
+
+        then:
+        er.data != null
+        er.data.foo == null
+        er.errors[0].path.toList() == ["foo"]
+    }
+}