Custom scalar types in GraphQL schema language?

[ggregoire]

Hi,

I tried to use a custom scalar type Date in my schema, written with the GraphQL schema language.

It seems that buildSchema takes only one param.
Is there a way to "register" my custom type in order to let buildSchema know what is the Date type?

import { buildSchema } from 'graphql';
import { GraphQLScalarType } from 'graphql/type';

const Date = new GraphQLScalarType({
  name: 'Date',
  serialize(value) {
    return value;
  },
});

const schema = buildSchema(`
  scalar Date

  type User {
    id: Int
    firstName: String
    lastName: String
    sex: String
    birthDate: Date
  }

  type Query {
    users(id: Int): [User]
  }
`);

const root = {
  users: async ({ id }) => {
    const users = db('users');
    return await id ? users.where('id', id) : users;
  },
}

The value of birthDate is 1986-02-11 07:13:14. I expect the same after the serialization.

My query in graphiQL:

{
  users(id: 1) {
    id
    firstName
    lastName
    sex
    birthDate
  }
}

The result:

{
  "data": {
    "users": [
      {
        "id": 1,
        "firstName": "Midas",
        "lastName": "Bokma",
        "sex": "m",
        "birthDate": null
      }
    ]
  },
  "errors": [
    {
      "message": "Expected a value of type \"Date\" but received: Tue Feb 11 1986 07:13:14 GMT-0600 (CST)",
      "locations": [
        {
          "line": 7,
          "column": 5
        }
      ]
    }
  ]
}

[helfer]

@ggregoire That won't work, because the const Date and the type Date won't refer to the same thing. buildSchema isn't really intended for making executable schemas, if you want to do that, you can use a library like graphql-tools instead.

[ggregoire]

Maybe not the right place to continue the discussion, but I got this error

Error: Type "Date" not found in document.

with the following simple code (almost a copy/paste of graphql-tools documentation)

makeExecutableSchema({
  typeDefs: [`
    scalar Date

    type User {
      id: Int
      firstName: String
      lastName: String
      sex: String
      birthDate: Date
    }

    type Query {
      users(id: Int): [User]
    }
  `],
  resolvers: {
    Query: {
      async users({ id }) {
        const users = db('users');
        return await id ? users.where('id', id) : users;
      }
    },
    Date: {
      __parseValue(value) {
        return new Date(value); // value from the client
      },
      __serialize(value) {
        return value.getTime(); // value sent to the client
      },
      __parseLiteral(ast) {
        if (ast.kind === Kind.INT) {
          return parseInt(ast.value, 10); // ast value is always in string format
        }
        return null;
      }
    },
  }
});

[helfer]

@ggregoire yeah, you should open an issue on graphql-tools. But for what it's worth, I copy-pasted your exact code and it created a schema with the Date type just fine, so I'm not sure what's going on.

[ggregoire]

My bad, I let this in my code 🙄

const officialWay = buildSchema(`
  type User {
    id: Int
    firstName: String
    lastName: String
    sex: String
    birthDate: Date
  }

  type Query {
    users(id: Int): [User]
  }
`);

@helfer Thank you for the help!

[ffxsam]

@helfer I'm having the same exact issue @ggregoire was in the first post, but I can't make sense out of what transpired on this thread. makeExecutableSchema is from a module by Apollo, buildSchema appears to be official GraphQL. How is the official GraphQL schema builder not sufficient for creating a custom Date scalar? My schema looks like this:

module.exports = buildSchema(`
  # A JavaScript Date object.
  scalar DateTime

  # A geoframe object, which contains several polygons.
  type Geoframe {
    id: ID!
    # Device ID count.
    count: Int
    createdAt: DateTime!
    createdBy: User!
    polygons: [Polygon]
  }

  type Query {
    geoframes: [Geoframe]
  }
`);

The resolvers:

module.exports = {
  DateTime: new GraphQLScalarType({
    name: 'DateTime',
    description: 'Date custom scalar type',
    parseValue(value) {
      return new Date(value); // value from the client
    },
    serialize(value) {
      return value.getTime(); // value sent to the client
    },
    parseLiteral(ast) {
      if (ast.kind === Kind.INT) {
        return parseInt(ast.value, 10); // ast value is always in string format
      }
      return null;
    },
  }),
  geoframes() {
    return new Promise((resolve, reject) => {
      Geoframe.find({}, (err, docs) => {
        const newDocs = docs.map(doc =>
          Object.assign({}, doc.toObject(), {
            createdAt: doc._id.getTimestamp(),
          })
        );

        resolve(newDocs);
      });
    });
  },
};

[klebba]

@ffxsam What approach did you land on? I agree that it is bizarre that there is no obvious solution beyond going outside the library.

Edit: here's a solution:

https://stackoverflow.com/questions/47824603/graphql-custom-scalar-definition-without-graphql-tools

[mrdulin]

@ffxsam Hi.

parseValue(value) {
  return new Date(value); // value from the client
},

What does value from the client mean?

[ffxsam]

@mrdulin The GraphQL client side. So, for example, if Apollo sends a mutation to the GraphQL server to update a date value.

[christopher-caldwell]

@ffxsam What approach did you land on? I agree that it is bizarre that there is no obvious solution beyond going outside the library.

Edit: here's a solution:

https://stackoverflow.com/questions/47824603/graphql-custom-scalar-definition-without-graphql-tools

The solution in the post worked for me, although with v15.3.0 ( not latest ), I had to do: Object.assign(schema.getTypeMap().Date, DateScalar)

I feel like this should be better documented. Every example I could find on google, SO, etc was with Apollo. The scalar section of the docs is very small, and doesn't cover this at all.