graphql-http

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GraphQL on HTTP middleware with built-in validations and GraphQL playground

Features

What

It provides GraphQL on HTTP middleware that can be embedded in any server.

Essentially, it takes a Request object and returns a Response object.

In the meantime, it performs HTTP request validation, processes GraphQL, and response object with the appropriate status code and message.

There is also a built-in GraphQL Playground.

Example

A simple example of creating a GraphQL server.

std/http + grpahql.js

import { graphqlHttp } from "https://deno.land/x/graphql_http@$VERSION/mod.ts";
import {
  Handler,
  serve,
  Status,
} from "https://deno.land/std@$VERSION/http/mod.ts";
import { buildSchema } from "https://esm.sh/graphql@$VERSION";

const graphqlResponse = graphqlHttp({
  schema: buildSchema(`type Query {
    hello: String!
  }`),
  rootValue: {
    hello: () => "world",
  },
  playground: true,
});

const handler: Handler = (req) => {
  const { pathname } = new URL(req.url);
  if (pathname === "/graphql") {
    return graphqlResponse(req);
  }
  return new Response("Not Found", {
    status: Status.NotFound,
  });
};

serve(handler);

Spec

This project is implemented in accordance with GraphQL over HTTP Spec.

We are actively implementing IETF RFC 2119 SHOULD and RECOMMENDED.

Request Parameters

A GraphQL-over-HTTP request is formed of the following parameters:

Name Required Description
query :white_check_mark: A Document containing GraphQL Operations and Fragments to execute. Must be a string.
operationName - The name of the Operation in the Document to execute.
GET: If present, must be a string.
variables - Values for any Variables defined by the Operation.
GET: If present, must be represented as a URL-encoded JSON string.

Response Status

The following responses may be returned.

Status Condition
200 If GraphQL is actually executed, even if it contains Field errors.
400 A required parameter does not exist. Illegal format of parameter.
405 When a mutation operation is requested on GET request.
406 The client Accept HTTP header does not contain at least one of the supported media types.
415 The client Content-type HTTP header does not contain at least one of the supported media types.
500 If the server encounters an unexpected error.

Below are the specific conditions under which each may occur. Errors are classified into four major categories.

  • HTTP Request errors
  • (GraphQL) Request errors
  • (GraphQL) Field errors
  • Unknown errors

HTTP Request errors

HTTP Request errors are errors in the http protocol. This refers to errors that can occur between HTTP and GraphQL, such as missing/incorrect values for required parameters, missing/incorrect values for required headers, etc.

Since these are client-side errors, the appropriate 4XX status is returned.

Request errors

Request errors are defined at [GraphQL Spec] 7.Response - Request errors.

Note here that the status code may be different depending on the Content-Type.

application/json

If Content-Type is application/json, all results of GraphQL Requests including GraphQL validation will be treated as 200 status.

See the [GraphQL over HTTP 6.4.1] application/json#Note for the reason for this.

application/graphql+json

If Content-Type is application/graphql+json, it is possible to respond with a status code other than 200 depending on the result of the GraphQL Request.

If the GraphQL request is invalid (e.g. it is malformed, or does not pass validation) then the response with 400 status code.

Field errors

Field errors are defined at [GraphQL Spec 7.Response] - Field errors.

Even if a Field error occurs, it will always be a 200 status code.

Unknown errors

If an error other than the above occurs on the server side, a 500 status code will be responded.

Upgrade to application/graphql+json

As you may have noticed, application/graphql+json represents a more accurate semantics response.

If you want application/graphql+json content, you must put application/graphql+json as a higher priority than application/json in the Accept header.

Example: Accept: application/graphql+json,application/json.

application/graphql+json vs application/json

Response status

application/graphql+json application/json
HTTP Request error 4XX(eg.406, 415) 4XX
GraphQL request error 400 200
GraphQL field error 200 200
Unknown(Internal server) error 5XX 5XX

Overwrite response

grpahqlHttp creates a response according to the GraphQL over HTTP specification. You can customize this response.

Example of adding a header:

import { graphqlHttp } from "https://deno.land/x/graphql_http@$VERSION/mod.ts";
import { buildSchema } from "https://esm.sh/graphql@$VERSION";

const responser = graphqlHttp({
  response: (res, ctx) => {
    if (ctx.request.method === "GET") {
      res.headers.set("Cache-Control", "max-age=604800");
    }
    return res;
  },
  schema: buildSchema(`type Query {
    hello: String
  }`),
});

Where the subscription?

Unfortunately, there is currently no specification for subscription and it is not implemented.

You can refer to other projects' implementations using SSE or Websocket.

API

graphqlHttp

Make a GraphQL Response Object that validate to Request Object.

Parameters

Name Required / Default Description
schema :white_check_mark: GraphQLSchema
The GraphQL type system to use when validating and executing a query.
source - Source | string
A GraphQL language formatted string representing the requested operation.
rootValue - unknown
The value provided as the first argument to resolver functions on the top level type (e.g. the query object type).
contextValue - unknown
The context value is provided as an argument to resolver functions after field arguments. It is used to pass shared information useful at any point during executing this query, for example the currently logged in user and connections to databases or other services.
variableValues - <{ readonly [variable: string: unknown; }> | null
A mapping of variable name to runtime value to use for all variables defined in the requestString.
operationName - string | null
The name of the operation to use if requestString contains multiple possible operations. Can be omitted if requestString contains only one operation.
fieldResolver - GraphQLFieldResolver<any, any> | null
A resolver function to use when one is not provided by the schema. If not provided, the default field resolver is used (which looks for a value or method on the source value with the field's name).
typeResolver - GraphQLTypeResolver<any, any> | null
A type resolver function to use when none is provided by the schema. If not provided, the default type resolver is used (which looks for a __typename field or alternatively calls the isTypeOf method).
response - (req: Request, ctx: RequestContext) => Promise<Response> | Response
Overwrite actual response.
playground - boolean
Whether enabled graphql-playground or not.
playgroundOptions { endpoint: "/graphql" } RenderPageOptions
graphql-playground options.

ReturnType

(req: Request) => Promise<Response>

Throws

  • AggregateError - When graphql schema validation is fail.

gqlFetch

GraphQL client with HTTP.

Example

import { gqlFetch } from "https://deno.land/x/graphql_http@$VERSION/mod.ts";

const { data, errors, extensions } = await gqlFetch({
  url: `<graphql-endpoint>`,
  query: `query Greet(name: $name) {
    hello(name: $name)
  }`,
}, {
  variables: {
    name: "Bob",
  },
  operationName: "Greet",
  method: "GET",
});

Generics

  • T extends jsonObject - data field type

Parameters

N Name Required / Default Description
1 params :white_check_mark: Parameters
url :white_check_mark: string | URL
GraphQL URL endpoint.
query :white_check_mark: string
GraphQL query
2 options - Options
variables - jsonObject
GraphQL variables.
operationName - string
GraphQL operation name.
method "POST" "GET" | "POST" | ({} & string)
HTTP Request method. According to the GraphQL over HTTP Spec, all GraphQL servers accept POST requests.
3 requestInit - RequestInit
Request init for customize HTTP request.
type json =
  | string
  | number
  | boolean
  | null
  | { [k: string]: json }
  | json[];

type jsonObject = {
  [k: string]: json;
};

ReturnTypes

Promise<Result<T>>

Throws

  • TypeError
  • DOMException
  • AggregateError

createRequest

Create GraphQL Request object.

Example

import { createRequest } from "https://deno.land/x/graphql_http@$VERSION/mod.ts";

const [request, err] = createRequest({
  url: "<graphql-endpoint>",
  query: `query Greet(name: $name) {
    hello(name: $name)
  }`,
  method: "GET",
});

if (!err) {
  const res = await fetch(request);
}

Parameters

N Name Required / Default Description
1 params :white_check_mark: Parameters
url :white_check_mark: string | URL
GraphQL URL endpoint.
query :white_check_mark: string
GraphQL query
method :white_check_mark: "GET" | "POST" | ({} & string)
HTTP Request method. According to the GraphQL over HTTP Spec, all GraphQL servers accept POST requests.
2 options - Options
variables - jsonObject
GraphQL variables.
operationName - string
GraphQL operation name.

ReturnType

[data: Request, error: undefined] | [data: undefined, error: TypeError]

Recipes

License

Copyright © 2022-present TomokiMiyauci.

Released under the MIT license