Fine-grained support for null values.

[alexdupre]

At the moment when a GraphQL query is generated it's possible to decide how to handle None values with the dropNullInputValues parameter, but this applies to all fields.

Unfortunately there are services that have semantic differences between a null value and a missing value, and requires a mix of both options in the same mutation. Shopify is one of this services, and currently it's impossible to use caliban to perform some operations because there isn't a fine grained control over it.

Honestly I don't know what might be the best approach to fix this issue.

[ghostdogpr]

There's an alternative way which is using a custom ArgEncoder, see the example here: #1272 (comment)

Would that work for you?

[alexdupre]

Thanks. If I'm understanding it correctly, it can work only with dropNullInputValues = false and by explicitely removing the null values for the encoding, not in the oppose way (default drop, with just a few specified), is it right?
Not super convenient, but it might work.

As an alternative I was thinking to add a new codegen parameter useNullableInputs to replace the binary Option with a ternary (or quaternary) Nullable type (accepting Null/Missing/Value(T) and Undefined) in the generated code. Would it make sense and something that you might want to merge?

[ghostdogpr]

I like the idea! What's Undefined for?

[alexdupre]

I confirm that setting dropNullInputValues = false and creating an ArgEncoder with a limited set of fields solved the issue. Thanks.

Undefined could be a 4th option to follow the dropNullInputValues behavior:

• Null enforces null
• Missing enforces dropping the field entirely
• Value(T) sets the field
• (Optional) Undefined uses the dropNullInputValues to determine the behavior