Support multiple schemas

[arnarthor]

This adds an additional optional parameter to the ppx usage where you can locally override the desired schema to validate the query against.

This is fully backwards compatible with the old API and only extends it to allow for usage such as this

Reason

module MyQuery = [%graphql
  {|
    query pokemon($id: String, $name: String) {
      pokemon(name: $name, id: $id) {
        id
        name
      }
    }
  |};
  {schema: "pokedex_schema.json"}
];

OCaml

module MyQuery = [%graphql
  {|
    query pokemon($id: String, $name: String) {
      pokemon(name: $name, id: $id) {
        id
        name
      }
    }
  |};;
  {schema = "pokedex_schema.json"}
];

By adding this extra parameter, the PPX now supports having multiple different GraphQL APIs in a single project without the need for yarn workspaces or similar solutions.

[arnarthor]

I wasn't able to run the bucklescript tests without the same changes as #50 had.

[baransu]

Thank you! It's a really good addition. What do you think about adjusting second param to support more fine-tuning like generating serialize function? #20 (comment)

[arnarthor]

That sounds really good @baransu. So for this PR, instead of having this secondary argument as a string, having it as an object instead? Some thing like

module MyQuery = [%graphql
  {|
    query pokemon($id: String, $name: String) {
      pokemon(name: $name, id: $id) {
        id
        name
      }
    }
  |};
  {schema: "pokedex_schema.json"}
];

[baransu]

Exactly like this. I'm only afraid of how it would work with optional arguments when you want to specify only part of additional params.

[arnarthor]

Having it as an object instead of record should solve that right?

That way it doesn't really need to be a certain type/shape. The PPX can just look for different values of the object

[arnarthor]

It means you can put in stuff that isn't doing anything, but at least we won't need to specify keys that we want default values to apply to?

[arnarthor]

I'll experiment and ping you when I have an update. I think the suggestion above should just work as is 👍

[arnarthor]

@baransu I've changed it to be a record. This works for any object since the PPX runs before the type checker.

To support other fields all you need to add is a separate function for the specific field you want similar to the extract_schema_from_config function

[baransu]

Great PR. Thank you @arnarthor. I only have few comments about code quality 🙂

[baransu]

Please change to |> based tests. I think it's more readable that way.

[arnarthor]

👍

[baransu]

Could we use labeled args here? It's getting pretty unreadable with more than 3 args.

[baransu]

maybe_schema can then be ~schema=?

[arnarthor]

👍

[arnarthor]

Because the parameter is explicitly an option in the downstream functions having it as ~schema=None instead made things easier to read.

If you explicitly want it as ~schema=? I can change it. But thought it didn't really matter myself

[arnarthor]

Wait, I might have misunderstood the initial comment. Did you want all parameters to be named?

[baransu]

Can be all, can be just schema 🙂

[arnarthor]

I think this is ready now @baransu 🎉

[baransu]

@arnarthor Could you add it also to README?

[baransu]

Thank you! LGTM 🎉

[baransu]

Releases as 0.4.6