GraphQL.js

Common errors

• Cannot query field "X" on type "Y". Did you mean "Z"?

  cause The requested field 'X' does not exist on the specified type 'Y' in your GraphQL schema. This is often due to a typo in the query or a missing field definition in the schema.
  fix Check your GraphQL schema for the correct field name on type 'Y', or verify your query for typos matching an existing field.

• Expected 'RootQueryType' to be an object type, got 'null'.

  cause The schema definition is missing or incorrectly defining one of the root operation types (Query, Mutation, Subscription) as a non-object type or `null`.
  fix Ensure your `buildSchema` or schema definition correctly defines 'Query', 'Mutation', and 'Subscription' as object types (e.g., `type Query { ... }`).

• Variable "$variableName" of type "TypeName!" was provided invalid value.

  cause A variable passed to the GraphQL query does not match the expected type defined in the schema, or a non-nullable variable was provided a `null` value.
  fix Check the type definition of `$variableName` in your GraphQL query and schema, and ensure the provided value conforms to that type and nullability constraints.

• A field named "fieldName" already exists on type "TypeName"

  cause Your GraphQL schema definition has duplicate field names on the same type, which is not allowed according to the GraphQL specification.
  fix Rename or remove the duplicate field definitions in your GraphQL schema to ensure all fields on a given type have unique names.

Warnings

• deprecated The `assertValidExecutionArguments` utility function has been deprecated. While it still works, it's recommended to review its usage and consider more explicit validation within your application.
  Fix: Review its usage and consider alternative validation methods or direct execution, avoiding reliance on this specific utility.
• gotcha When creating plain JavaScript objects intended purely as hash maps (e.g., for GraphQL values or configurations), using `Object.create(null)` is recommended over `{}` to avoid prototype pollution issues and unintended inherited properties from the default object prototype.
  Fix: For simple hash map objects where prototype chain methods are not needed, initialize them with `Object.create(null)`.
• breaking In v17 alpha releases, the direct `info.abortSignal` property in resolvers for execution cancellation has been replaced by a method `info.getAbortSignal()`. Direct access to the property will no longer work.
  Fix: Update resolver implementations to call `info.getAbortSignal()` to access the `AbortSignal` for execution cancellation.
• breaking v17 alpha releases introduce stricter validation rules. This includes forbidding `@skip` and `@include` directives in subscription root selections, new validation for `@stream` directives applied to different instances of the same field, and rejection of deprecated fields when inferring input types.
  Fix: Review your GraphQL schema and query definitions to ensure they adhere to the updated validation rules for directives and deprecated fields, especially in subscription operations.

Install

• npm install graphql npm
• yarn add graphql yarn
• pnpm add graphql pnpm

Imports

• graphql
  wrong:

  const { graphql } = require('graphql');

  correct:

  import { graphql } from 'graphql';

• buildSchema
  wrong:

  const { buildSchema } = require('graphql');

  correct:

  import { buildSchema } from 'graphql';

Quickstart

This example demonstrates how to define a simple GraphQL schema, provide a resolver, and execute a basic query using GraphQL.js.

import { graphql, buildSchema } from 'graphql';

// Construct a schema, using GraphQL schema language
const schema = buildSchema(`
  type Query {
    hello: String
  }
`);

// The root provides a resolver function for each API endpoint
const root = {
  hello: () => {
    return 'Hello world!';
  },
};

// Run the GraphQL query '{ hello }' and print out the response
graphql({ schema, source: '{ hello }', rootValue: root }).then((response) => {
  console.log(response);
});