How to set NULL values in Stub as clientValue with Spring Cloud Contracts

Question

We are trying to set null values into the producer client site code.

Example of a Groovy contract:

Contract.make {
        description("Creating user")
        name("Create user")
        request {
            method 'POST'
            url '/api/user'
            body(
                    name: $(consumer(anyNonEmptyString()), producer('John Doe')),
                    address: $(consumer(optional(regex(alphaNumeric()))), producer(null))
            )
            headers {
                contentType(applicationJson())
            }
        }
        response {
            status 201
        }
    }

Following contract produces an assertion failed when trying to parse the Groovy contract:

assert testSide ==~ Pattern.compile(stubSide.optionalPattern())
   |        |           |       |        |
   null     false       |       |        ([a-zA-Z0-9]+)?
                        |       ([a-zA-Z0-9]+)?
                        ([a-zA-Z0-9]+)?

Any suggestion to set it to null in the generated class to get a result like this (or simply not adding the field address:

@Test
public void create_user() throws Exception {
    // given:
        MockMvcRequestSpecification request = given()
                .header("Content-Type", "application/json")
                .body("{\"name\":\"John Doe\",\"address\": null,");

    // when:
        ResponseOptions response = given().spec(request)
                .post("/api/user");

    // then:
        assertThat(response.statusCode()).isEqualTo(201);
}

Answer 1

There was an issue in Spring Cloud Contract that we treated an optional property as a value that is set to either empty or non-empty, but it had to be there. With fixing of https://github.com/spring-cloud/spring-cloud-contract/issues/1257 we've also added support for null value.