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-graphqlHow 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 OBJECTwhere 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 exampleRoadmap
- provide CLI
- provide examples