Better support for GraphQL directives

Continue the discussion from here: https://github.com/dotansimha/graphql-code-generator/pull/561

The idea is to have better support for directives such as @skip, @include, and other custom directives that become common such as @client.

[JuHwon]

i am also having an issue because i am using AWS AppSync, i got a directive @aws_subscribe in my schema. the cli returns: error: Directive aws_subscribe: Couldn't find type aws_subscribe in any of the schemas.

a nice way to handle custom/popular directives would be awesome.

[JuHwon]

Yes, my aws-enhancements.graphql contains my aws specific schema enhancements so the codegen knows about e.g. the @aws_subscribe directive. I basically followed this documentation and also checked out the already provided templates.

Since I am using this codegen for my typescript backend only I do not need the @connection directive or any other query types. (I am planning to also introduce this codegen in the frontend in the future. Though for now, I am only generating the model types for my TS backend.) My aws-enhancements.graphql is very minimal for now:

directive @aws_subscribe(mutations: [String!]!) on FIELD_DEFINITION

The way I came to this solution was by checking out the mongodb template directives. This way the codegen knows about the directive and it’s valid. I bet you can do the same with your @connection directive.

When providing a custom schema in your codegen project config I think you don’t even need to write your custom templates too. Though if you want to, I also found the types available in the handlebars templates: https://github.com/dotansimha/graphql-code-generator/blob/master/packages/graphql-codegen-core/src/types.ts With these typedefs and the already provided template source code it was very easy to create my custom templates the way I need it in my project.

So imo the graphql-code-generator does not require a better support for 3rd party directives since actually, it’s already easy to integrate them. Maybe the documentation about it should be improved. So users, who actually need custom schema enhancements get an easy manual to do so.