graphql-to-reason

This tool will transform existing GraphQL schema to ReasonML types to be used on server side.

Installation

First, add this package as a dependency to your package.json

yarn add --dev graphql-to-reason
# or, if you use npm:
npm install -D graphql-to-reason

graphql-to-reason requires json variant (aka introspection query) of schema.graphql.

schema.json can be generated with npx graphql-to-reason-schema schema.graphql schema.json.

Integration with Bucklescript can be done via generators

a) With already introspected schema

{
  "generators": [
    {
      "name": "generate-schematypes",
      "command": "npx graphql-to-reason $in $out"
    }
  ],
  "sources": [
    {
      "dir": "src",
      "generators": [
        {
          "name": "generate-schematypes",
          "edge": [ "SchemaTypes_builder.re", ":", "schema.json"]
        }
      ]
    }
  ]
}

b) From .graphql

{
  "generators": [
    {
      "name": "generate-schematypes",
      "command": "npx graphql-to-reason-schema $in $in.json  && npx graphql-to-reason $in.json $out"
    }
  ],
  "sources": [
    {
      "dir": "src",
      "generators": [
        {
          "name": "generate-schematypes",
          "edge": ["SchemaTypes_builder.re", "schema.graphql.json", ":", "schema.graphql"]
        }
      ]
    }
  ]
}

Examples

Simple schema.graphql

scalar Click

type Query {
    clicks: Click!
}

type Mutation {
    click(payload: String!): Click!
}

Next we generate ReasonML code from it: npx graphql-to-reason schema.json SchemaTypes_builder.re

It will output SchemaTypes_builder.re to use it in other modules:

include SchemaTypes_builder.MakeSchema({
  /* we need to configure our server types:
      - all scalar types
      - resolver type
      - custom directive resolver type  */
  module Scalars = {
    type click = int;
  };

  /* args - our arguments Array
     fieldType - original field type
     result - resoved value (for example Js.Nullable.t(fieldType)) */
  type resolver('args, 'fieldType, 'result) =
    (
      unit,
      'args,
      /*context args depend on your graphql setup*/
      ServerContext.t,
      ServerContext.ResolveInfo.t,
      ServerContext.FieldInfo.t('fieldType)
    ) =>
    Js.Promise.t('result);
  type directiveResolver('payload);
});


module Clicks = {
  let count = ref(0);
  /* No need to explicitly type resolver, it will infer correct type later */
  let resolver = (_node, _args, _context, _resolveInfo, _fieldInfo) =>
    Js.Promise.make((~resolve, ~reject) => {
      count := count^ + 1;
      resolve(count^);
    });
};


/* Clicks.resolver now infers SchemaTypes.Mutation.clicksCount type */
let mutationResolvers =
  SchemaTypes.Mutation.t(~clicksCount=Clicks.resolver, ());

let resolvers = SchemaTypes.t(~mutation, ());

createMyGraphqlServer(resolvers);

Developing

Install esy:

npm install -g esy@latest

Install dependencies:

make install

To build executables:

make build

To run tests:

make test