Transform GraphQL

We use GraphQL transformers. Examples are Graphback, Dgraph, AWS Amplify. This library provides function that given any GraphQL schema creates new GraphQL schemas basing on transformer functions.

Installation

npm i transform-graphql

How it works

Provide original schema with your transformer directives and an array of transformer functions defined by TransformerDef type

import { TransformGraphQLSchema } from 'transform-graphql';

const transformedSchema = TransformGraphQLSchema({ 
    schema: inputSchema, 
    transformers: [transformerCRUD] 
});

This short example simply shows what transform GraphQL is about:

Given the schema:

type Post @model{
    name: String!
    content: String!
    createdAt: String!
}

type Query{
    version:String
}
type Mutation{
    version:String
}

directive @model on OBJECT

where model is our actual transformer

We expect schema to be transformed into

directive @model on OBJECT

input CreatePost{
    name: String!
    content: String!
    createdAt: String!
}

input DetailsPost{
    id: String!
}

type Mutation{
    version: String
    post: PostMutation
}

type Post @model{
    name: String!
    content: String!
    createdAt: String!
}

type PostMutation{
    create(
            post: CreatePost
    ): String!
    update(
            post: UpdatePost
            details: DetailsPost
    ): String!
    remove(
            details: DetailsPost
    ): String!
}

type PostQuery{
    list: [Post!]!
    getByDetails(
            details: DetailsPost
    ): Post
}

type Query{
    version: String
    post: PostQuery
}
input UpdatePost{
    name: String!
    content: String!
    createdAt: String!
}
schema{
    query: Query,
    mutation: Mutation
}

And the transformer code should look like this

const inputSchema = `
type Post @model{
    name: String!
    content: String!
    createdAt: String!
}

type Query{
    version:String
}
type Mutation{
    version:String
}`
const transformerCRUD: TransformerDef = {
  transformer: ({ field, operations }) => {
    if (!field.args) {
      throw new Error('Model can be used only for types');
    }
    if (!operations.query) {
      throw new Error('Query type required');
    }
    if (!operations.mutation) {
      throw new Error('Query type required');
    }
    return `
      input Create${field.name}{
          ${TreeToGraphQL.parse({ nodes: field.args })}
      }
      input Update${field.name}{
          ${TreeToGraphQL.parse({ nodes: field.args })}
      }
      input Details${field.name}{
          id: String!
      }
      type ${field.name}Query{
          list: [${field.name}!]!
          getByDetails(details: Details${field.name}): ${field.name}
      }
      type ${field.name}Mutation{
          create( ${field.name[0].toLowerCase() + field.name.slice(1)}: Create${field.name} ): String!
          update( ${field.name[0].toLowerCase() + field.name.slice(1)}: Update${field.name}, details: Details${
      field.name
    } ): String!
          remove( details: Details${field.name} ): String!
      }
      extend type ${operations.query.name}{
          ${field.name[0].toLowerCase() + field.name.slice(1)}: ${field.name}Query
      }
      extend type ${operations.mutation.name}{
          ${field.name[0].toLowerCase() + field.name.slice(1)}: ${field.name}Mutation
      }
      `;
  },
  directiveName: 'model',
};
const transformedSchema = TransformGraphQLSchema({ schema: GraphQLTransform, transformers: [transformerCRUD] });
//transfomed schema should look like in the example

Roadmap

• provide CLI
• provide examples