fix(args): stop creating properties for nullable args fields

src/resolvers/convert-args.ts

@@ -126,8 +126,11 @@ export function convertArgsToInstance(argsMetadata: ArgsParamMetadata, args: Arg
 
   const transformedFields = argsFields.reduce<Record<string, any>>((fields, field) => {
     const fieldValue = args[field.name];
-    const fieldTarget = field.getType();
-    fields[field.name] = convertValuesToInstances(fieldTarget, fieldValue);
+    // don't create property for nullable field
+    if (fieldValue !== undefined) {
+      const fieldTarget = field.getType();
+      fields[field.name] = convertValuesToInstances(fieldTarget, fieldValue);
+    }
     return fields;
   }, {});
 

tests/functional/resolvers.ts

@@ -1152,6 +1152,16 @@ describe("Resolvers", () => {
       }
       classes.SampleArgs = SampleArgs;
 
+      @ArgsType()
+      class SampleOptionalArgs {
+        @Field()
+        stringField: string;
+
+        @Field({ nullable: true })
+        optionalField?: string;
+      }
+      classes.SampleOptionalArgs = SampleOptionalArgs;
+
       @InputType()
       class SampleInput {
         private readonly TRUE = true;
@@ -1300,6 +1310,12 @@ describe("Resolvers", () => {
           }
         }
 
+        @Mutation()
+        mutationWithOptionalArgs(@Args() args: SampleOptionalArgs): boolean {
+          mutationInputValue = args;
+          return true;
+        }
+
         @Mutation()
         mutationWithInput(@Arg("input") input: SampleInput): number {
           if (input.isTrue()) {
@@ -1553,6 +1569,18 @@ describe("Resolvers", () => {
       expect(result).toBeLessThanOrEqual(10);
     });
 
+    it("shouldn't create properties of nullable args", async () => {
+      const mutation = `mutation {
+        mutationWithOptionalArgs(stringField: "stringField")
+      }`;
+
+      const { errors } = await graphql(schema, mutation);
+
+      expect(errors).toBeUndefined();
+      expect(mutationInputValue).toBeInstanceOf(classes.SampleOptionalArgs);
+      expect(mutationInputValue).not.toHaveProperty("optionalField");
+    });
+
     it("should create instance of input object", async () => {
       const mutation = `mutation {
         mutationWithInput(input: { factor: 10 })