How to extend the GraphQL Schema?
Each plugin can also specify addToSchema field, and to extend the GraphQLSchema with more types:
module.exports = {
plugin(schema, documents, config) {
const typesMap = schema.getTypeMap()
return Object.keys(typesMap).join('\n')
},
addToSchema: /* GraphQL */ `
type MyType {
field: String
}
directive @myDirective on OBJECT
`
}It's useful when you wish to add things like declarative @directive to your GraphQLSchema, which affects only the output of the codegen.
For example, let's add a custom @directive that tells the codegen to ignore a specific type:
module.exports = {
plugin(schema, documents, config, info) {
const typesMap = schema.getTypeMap()
return Object.keys(typesMap)
.filter(typeName => {
const type = typesMap[typeName]
const { astNode } = type
if (astNode?.directives?.find(d => d.name.value === 'ignore')) {
return false
}
return true
})
.join('\n')
},
addToSchema: /* GraphQL */ `
directive @ignore on OBJECT
`
}