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Transforms
Filtering

Filtering

Filter transforms are constructed with a filter function that returns a boolean. The transform executes the filter on each schema element within its scope and rejects elements that do not pass the filter.

Filtering Types

You can filter any named element types based on the given filter function;

class FilterTypes(filterTypeFn: FilterTypeFn) implements Transform
 
type FilterTypeFn = (type: GraphQLNamedType) => boolean

The following transform definition removes all types ending with _Secret from the schema;

import { FilterTypes } from '@graphql-tools/wrap'
 
const subschema = {
  schema,
  executor,
  transforms: [new FilterType(namedType => !namedType.endsWith('_Secret'))]
}

Filtering Root Fields

You can filter the fields of the root types such as Query, Mutation, and Subscription based on the given filter function;

class FilterRootFields(filterRootFieldFn: FilterRootFieldFn) implements Transform
 
type FilterRootFieldFn = (operation: 'Query' | 'Mutation' | 'Subscription', fieldName: string, fieldConfig: GraphQLFieldConfig<any, any>) => boolean

The following transform definition removes all fields starting with _secret from the schema;

import { FilterRootFields } from '@graphql-tools/wrap'
 
const subschema = {
  schema,
  executor,
  transforms: [new FilterRootFields((operation, fieldName, fieldConfig) => !fieldName.startsWith('_secret'))]
}

Filtering Object, Interface or Input Object Fields

You can filter the fields of object types based on the given filter function;

class FilterObjectFields(filterObjectFieldFn: FilterObjectInterfaceFieldFn) implements Transform
class FilterInterfaceFields(filterInterfaceFieldFn: FilterObjectInterfaceFieldFn) implements Transform
 
type FilterObjectInterfaceFieldFn = (typeName: string, fieldName: string, fieldConfig: GraphQLFieldConfig<any, any>) => boolean
class FilterInputObjectFields(filterInputObjectFieldFn: FilterInputObjectFieldFn) implements Transform
 
type FilterInputObjectFieldFn = (typeName: string, fieldName: string, fieldConfig: GraphQLInputFieldConfig) => boolean

The following transform definition removes all interface fields starting with _secret from the schema;

import { FilterInterfaceFields } from '@graphql-tools/wrap'
 
const subschema = {
  schema,
  executor,
  transforms: [new FilterInterfaceFields((typeName, fieldName, fieldConfig) => !fieldName.startsWith('_secret'))]
}

Filtering Object Field Directives

You can filter the directives of object fields based on the given filter function;

class FilterObjectFieldDirectives(filterObjectFieldDirectiveFn: FilterObjectFieldDirectiveFn) implements Transform
 
type FilterObjectFieldDirectiveFn = (directiveName: string, directiveValue: any) => boolean

The following transform definition removes all directives unless the directive name is keep and the directive argument arg is not 1;

import { FilterObjectFieldDirectives } from '@graphql-tools/wrap'
 
const schema = buildSchema(/* GraphQL */ `
  directive @remove on FIELD_DEFINITION
  directive @keep(arg: Int) on FIELD_DEFINITION
  type Query {
    alpha: String @remove
    bravo: String @keep
    charlie: String @keep(arg: 1)
    delta: String @keep(arg: 2)
  }
`)
 
const subschema = {
  schema,
  transforms: [
    new FilterObjectFieldDirectives((dirName: string, dirValue: any) => dirName === 'keep' && dirValue.arg !== 1)
  ]
}

So the resulting schema will be;

type Query {
  alpha: String
  bravo: String @keep
  charlie: String
  delta: String @keep(arg: 2)
}
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