Fragment Operations

/**
 * Convert a fragment document into an executable query document
 * @param document - GraphQL document containing fragment definitions
 * @param fragmentName - Name of specific fragment to use (optional if document has only one fragment)
 * @returns Query document that spreads the specified fragment
 * @throws Error if document contains operations or if fragmentName is needed but not provided
 */
function getFragmentQueryDocument(
  document: DocumentNode,
  fragmentName?: string
): DocumentNode;

import { getFragmentQueryDocument } from "apollo-utilities";
import { parse } from "graphql";

// Single fragment document
const fragmentDoc = parse(`
  fragment UserInfo on User {
    id
    name
    email
  }
`);

const queryDoc = getFragmentQueryDocument(fragmentDoc);
console.log(print(queryDoc));
// query {
//   ...UserInfo
// }
// 
// fragment UserInfo on User {
//   id
//   name
//   email
// }

// Multiple fragments document - need to specify fragment name
const multiFragmentDoc = parse(`
  fragment UserInfo on User {
    id
    name
    email
  }
  
  fragment PostInfo on Post {
    id
    title
    content
  }
`);

const userQueryDoc = getFragmentQueryDocument(multiFragmentDoc, "UserInfo");
console.log(print(userQueryDoc));
// query {
//   ...UserInfo
// }
// 
// fragment UserInfo on User {
//   id
//   name
//   email
// }
// 
// fragment PostInfo on Post {
//   id
//   title
//   content
// }

// This will throw an error because it contains a query operation
const invalidDoc = parse(`
  query GetUser {
    user { name }
  }
  
  fragment UserInfo on User {
    id
    name
  }
`);

try {
  getFragmentQueryDocument(invalidDoc);
} catch (error) {
  console.log(error.message); 
  // "Found a query operation named 'GetUser'. No operations are allowed when using a fragment as a query."
}

// This will throw an error because fragmentName is required for multiple fragments
const multiDoc = parse(`
  fragment UserInfo on User { id name }
  fragment PostInfo on Post { id title }
`);

try {
  getFragmentQueryDocument(multiDoc); // Missing fragmentName
} catch (error) {
  console.log(error.message);
  // "Found 2 fragments. `fragmentName` must be provided when there is not exactly 1 fragment."
}

import { getFragmentQueryDocument } from "apollo-utilities";
import { execute } from "graphql";

const fragment = parse(`
  fragment UserProfile on User {
    id
    name
    email
    profile {
      bio
      avatar
    }
  }
`);

// Convert to executable query
const query = getFragmentQueryDocument(fragment);

// Now you can execute it against a GraphQL schema
const result = await execute({
  schema: mySchema,
  document: query,
  rootValue: { user: mockUserData }
});

import { getFragmentQueryDocument } from "apollo-utilities";

const baseFragment = parse(`
  fragment BaseUser on User {
    id
    name
  }
`);

// Get the query version of the fragment
const fragmentQuery = getFragmentQueryDocument(baseFragment);

// The resulting query can be further composed or analyzed
const operation = getOperationDefinition(fragmentQuery);