How jspecify fits with builder pattern?

[a]

Hello. I have immutable bean with lots of fields and builder for it:

@NullMarked
public class A {

  private final String hello;
  private final @Nullable Integer world;

  public static Builder newBuilder() {
    return new Builder();
  }

  public A(String hello, @Nullable Integer world) {
    this.hello = Objects.requireNonNull(hello);
    this.world = world;

  }

  public String getHello() {
    return hello;

  }

  public @Nullable Integer getWorld() {

    return world;

  }

  public static class Builder {

    private String hello;

    private @Nullable Integer world;

    public String getHello() {

      return hello;

    }

    public void setHello(String hello) {

      this.hello = hello;

    }

    public @Nullable Integer getWorld() {

      return world;

    }

    public void setWorld(@Nullable Integer world) {

      this.world = world;

    }

    public A build() {
      return new A(hello, world);
    }

  }
}

IDE claims about hello field in builder (and CI system stops the build):

I can't initialize this field, because there's no suitable default value according to business logic of my object (even empty string). I can't mark this field as nullable, because this defeats main purpose of jspecify - take guidance for developer which fields are optional and which not.

It's ok that hello field takes null. Later it will be set by developer.

How to deal with this situation?

[Manu Sridharan]

Hi, I think the typical solution here is to mark the `Builder.hello` field as @Nullable and then to do an `Objects.requireNonNull(hello)` call in `Builder.build` to ensure that it has been set.  The property you want to enforce here is that on any Builder object, the `setHello` method is called before the `build` method, which is outside the scope of most nullness checkers.  The Called Methods Checker from the Checker Framework (which I helped to develop) is able to check this type of method call ordering property at compile time, but that is outside of JSpecify.

Best,

Manu 

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