57 non null fields

[ariannedee]

• Use Field(null=False) to mark a field as non-nullable
• If that field returns None, throw a field error
• In introspection, return NON_NULL as the type's kind, and ofType returns the original type

Issues:

• What do we do about ManyRelatedField(null=False)?
  • Must return a list with no null elements, but can return null
  • Must not return null, but can return an empty list or a list with null elements
  • Don't worry about it for now
• The only difference in the response between a field that returns None that is nullable and one that is not is that an error in the errors list is added to say that was not allowed. But if someone is not expecting that field to be null then tries to use the result without checking for errors, they will have problems. We also don't currently have a way of showing which error was for which field.
  • This is okay since it aligns with the specs
  • We should handle these a different way

Fixes #57

[melinath]

I think I'd prefer to see this all handled in get_value() rather than having a separate return_null method. It feels like it adds to the complexity of the object without a benefit of abstraction. I'd also rather not have a separate value property for the same reason, but I could see an argument for it in terms of ease of use of the API.

[ariannedee]

I would like to keep using get_value() as the main way to access the value, but since it is being implemented in a few different models (and might be overridden in custom models), I didn't want that part to need to be implemented in each one. Do you have a suggestion for a nicer way of handling this?

[melinath]

I think that it might be easier for folks to get used to the API if the attribute were also called null

[melinath]

checked boxes in the OP. Re: ManyRelatedField, I feel like the spec is kind of vague about this, but the intro to graphql is a bit more explicit. We should be able to handle nullable/non-null lists of nullable/non-null items.

I'm not quite sure how that would play with ManyRelatedField... I don't know what would lead to an item in a ManyRelatedField coercing to null. FWIW I'm inclined to say that the null should indicate whether the field itself can be null rather than whether its contained values can be.