use table enums in functions via domain in V5

[tsnobip]

Feature description

V4 has the feature to use table enums in functions via domain, I think we should port it to V5 too. I'm just not sure how to do it in V5 (possibly via build.setGraphQLTypeForPgCodec).

Motivating example

Same motivation as for the feature in V4, allowing to have nice GraphQL enums in function parameter / return types.

Breaking changes

not breaking as far as I know

Supporting development

I [tick all that apply]:

• am interested in building this feature myself
• am interested in collaborating on building this feature
• am willing to help testing this feature before it's released
• am willing to write a test-driven test suite for this feature (before it exists)
• am a Graphile sponsor ❤️
• have an active support or consultancy contract with Graphile

[tsnobip]

I made some experiments, something like this almost works:

{
      name: 'EnumDomainGraphQLTypePlugin',
      version: '0.0.0',
      schema: {
        hooks: {
          finalize(_, build) {
            for (const [key, codec] of Object.entries(build.input.pgRegistry.pgCodecs)) {
              if (codec.domainOfCodec?.name == 'text') {
                const name = build.inflection.builtin(codec.name.charAt(0).toUpperCase() + codec.name.slice(1, -4));
                build.setGraphQLTypeForPgCodec(codec, "output", name);
                build.setGraphQLTypeForPgCodec(codec, "input", name);
              }
            };
            return _;
          },
        },
      },
    }

The issue is that the domain is already registered as a scalar so it fails and I don't know how to deregister a scalar (or prevent it to get registered).

[benjie]

Indeed; this relates to:

• Implement new PostGraphile merges crystal-pre-merge#348

You shouldn't be using the finalize hook for this, it's way too late - that's the final step when the schema is built. Instead use the init hook, and have it run before PgCodecsPlugin:

schema: {
  hooks: {
    init: {
      before: ['PgCodecsPlugin'],
      callback(_, build) { ... }
    }
  }
}