graphql.py

import json
import typing

from starlette import status
from starlette.background import BackgroundTasks
from starlette.concurrency import run_in_threadpool
from starlette.requests import Request
from starlette.responses import HTMLResponse, JSONResponse, PlainTextResponse, Response
from starlette.types import Receive, Scope, Send

try:
    import graphene
    from graphql.error import GraphQLError, format_error as format_graphql_error
    from graphql.execution.executors.asyncio import AsyncioExecutor
except ImportError:  # pragma: nocover
    graphene = None
    AsyncioExecutor = None  # type: ignore
    format_graphql_error = None  # type: ignore
    GraphQLError = None  # type: ignore


class GraphQLApp:
    def __init__(
        self,
        schema: "graphene.Schema",
        executor: typing.Any = None,
        executor_class: type = None,
        graphiql: bool = True,
        format_error: typing.Optional[typing.Callable[Exception, dict]] = None,
    ) -> None:
        self.schema = schema
        self.graphiql = graphiql
        self._format_error_override = format_error
        if executor is None:
            # New style in 0.10.0. Use 'executor_class'.
            # See issue https://github.com/encode/starlette/issues/242
            self.executor = executor
            self.executor_class = executor_class
            self.is_async = executor_class is not None and issubclass(
                executor_class, AsyncioExecutor
            )
        else:
            # Old style. Use 'executor'.
            # We should remove this in the next median/major version bump.
            self.executor = executor
            self.executor_class = None
            self.is_async = isinstance(executor, AsyncioExecutor)

    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
        if self.executor is None and self.executor_class is not None:
            self.executor = self.executor_class()

        request = Request(scope, receive=receive)
        response = await self.handle_graphql(request)
        await response(scope, receive, send)

    async def handle_graphql(self, request: Request) -> Response:
        if request.method in ("GET", "HEAD"):
            if "text/html" in request.headers.get("Accept", ""):
                if not self.graphiql:
                    return PlainTextResponse(
                        "Not Found", status_code=status.HTTP_404_NOT_FOUND
                    )
                return await self.handle_graphiql(request)

            data = request.query_params  # type: typing.Mapping[str, typing.Any]

        elif request.method == "POST":
            content_type = request.headers.get("Content-Type", "")

            if "application/json" in content_type:
                data = await request.json()
            elif "application/graphql" in content_type:
                body = await request.body()
                text = body.decode()
                data = {"query": text}
            elif "query" in request.query_params:
                data = request.query_params
            else:
                return PlainTextResponse(
                    "Unsupported Media Type",
                    status_code=status.HTTP_415_UNSUPPORTED_MEDIA_TYPE,
                )

        else:
            return PlainTextResponse(
                "Method Not Allowed", status_code=status.HTTP_405_METHOD_NOT_ALLOWED
            )

        try:
            query = data["query"]
            variables = data.get("variables")
            operation_name = data.get("operationName")
        except KeyError:
            return PlainTextResponse(
                "No GraphQL query found in the request",
                status_code=status.HTTP_400_BAD_REQUEST,
            )

        background = BackgroundTasks()
        context = {"request": request, "background": background}

        result = await self.execute(
            query, variables=variables, context=context, operation_name=operation_name
        )
        error_data = (
            [self.format_error(err) for err in result.errors] if result.errors else None
        )
        response_data = {"data": result.data}
        if error_data:
            response_data["errors"] = error_data
        status_code = (
            status.HTTP_400_BAD_REQUEST if result.errors else status.HTTP_200_OK
        )

        return JSONResponse(
            response_data, status_code=status_code, background=background
        )

    def format_error(self, error: Exception) -> dict:
        fmt = self._format_error_override or format_graphql_error
        return fmt(error)

    async def execute(  # type: ignore
        self, query, variables=None, context=None, operation_name=None
    ):
        if self.is_async:
            return await self.schema.execute(
                query,
                variables=variables,
                operation_name=operation_name,
                executor=self.executor,
                return_promise=True,
                context=context,
            )
        else:
            return await run_in_threadpool(
                self.schema.execute,
                query,
                variables=variables,
                operation_name=operation_name,
                context=context,
            )

    async def handle_graphiql(self, request: Request) -> Response:
        text = GRAPHIQL.replace("{{REQUEST_PATH}}", json.dumps(request.url.path))
        return HTMLResponse(text)


GRAPHIQL = """
<!--
 *  Copyright (c) Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the license found in the
 *  LICENSE file in the root directory of this source tree.
-->
<!DOCTYPE html>
<html>
  <head>
    <style>
      body {
        height: 100%;
        margin: 0;
        width: 100%;
        overflow: hidden;
      }
      #graphiql {
        height: 100vh;
      }
    </style>
    <!--
      This GraphiQL example depends on Promise and fetch, which are available in
      modern browsers, but can be "polyfilled" for older browsers.
      GraphiQL itself depends on React DOM.
      If you do not want to rely on a CDN, you can host these files locally or
      include them directly in your favored resource bunder.
    -->
    <link href="//cdn.jsdelivr.net/npm/graphiql@0.12.0/graphiql.css" rel="stylesheet"/>
    <script src="//cdn.jsdelivr.net/npm/whatwg-fetch@2.0.3/fetch.min.js"></script>
    <script src="//cdn.jsdelivr.net/npm/react@16.2.0/umd/react.production.min.js"></script>
    <script src="//cdn.jsdelivr.net/npm/react-dom@16.2.0/umd/react-dom.production.min.js"></script>
    <script src="//cdn.jsdelivr.net/npm/graphiql@0.12.0/graphiql.min.js"></script>
  </head>
  <body>
    <div id="graphiql">Loading...</div>
    <script>
      /**
       * This GraphiQL example illustrates how to use some of GraphiQL's props
       * in order to enable reading and updating the URL parameters, making
       * link sharing of queries a little bit easier.
       *
       * This is only one example of this kind of feature, GraphiQL exposes
       * various React params to enable interesting integrations.
       */
      // Parse the search string to get url parameters.
      var search = window.location.search;
      var parameters = {};
      search.substr(1).split('&').forEach(function (entry) {
        var eq = entry.indexOf('=');
        if (eq >= 0) {
          parameters[decodeURIComponent(entry.slice(0, eq))] =
            decodeURIComponent(entry.slice(eq + 1));
        }
      });
      // if variables was provided, try to format it.
      if (parameters.variables) {
        try {
          parameters.variables =
            JSON.stringify(JSON.parse(parameters.variables), null, 2);
        } catch (e) {
          // Do nothing, we want to display the invalid JSON as a string, rather
          // than present an error.
        }
      }
      // When the query and variables string is edited, update the URL bar so
      // that it can be easily shared
      function onEditQuery(newQuery) {
        parameters.query = newQuery;
        updateURL();
      }
      function onEditVariables(newVariables) {
        parameters.variables = newVariables;
        updateURL();
      }
      function onEditOperationName(newOperationName) {
        parameters.operationName = newOperationName;
        updateURL();
      }
      function updateURL() {
        var newSearch = '?' + Object.keys(parameters).filter(function (key) {
          return Boolean(parameters[key]);
        }).map(function (key) {
          return encodeURIComponent(key) + '=' +
            encodeURIComponent(parameters[key]);
        }).join('&');
        history.replaceState(null, null, newSearch);
      }
      // Defines a GraphQL fetcher using the fetch API. You're not required to
      // use fetch, and could instead implement graphQLFetcher however you like,
      // as long as it returns a Promise or Observable.
      function graphQLFetcher(graphQLParams) {
        // This example expects a GraphQL server at the path /graphql.
        // Change this to point wherever you host your GraphQL server.
        return fetch({{REQUEST_PATH}}, {
          method: 'post',
          headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json',
          },
          body: JSON.stringify(graphQLParams),
          credentials: 'include',
        }).then(function (response) {
          return response.text();
        }).then(function (responseBody) {
          try {
            return JSON.parse(responseBody);
          } catch (error) {
            return responseBody;
          }
        });
      }
      // Render <GraphiQL /> into the body.
      // See the README in the top level of this module to learn more about
      // how you can customize GraphiQL by providing different values or
      // additional child elements.
      ReactDOM.render(
        React.createElement(GraphiQL, {
          fetcher: graphQLFetcher,
          query: parameters.query,
          variables: parameters.variables,
          operationName: parameters.operationName,
          onEditQuery: onEditQuery,
          onEditVariables: onEditVariables,
          onEditOperationName: onEditOperationName
        }),
        document.getElementById('graphiql')
      );
    </script>
  </body>
</html>
"""