Add context to the arguments of the extensions function (#441)

* Add context to the arguments of the extensions function

* Update the extensions function example in the read me to better reflect changes

README.md

@@ -86,7 +86,7 @@ The `graphqlHTTP` function accepts the following options:
     `"extensions"` field in the resulting JSON. This is often a useful place to
     add development time metadata such as the runtime of a query or the amount
     of resources consumed. This may be an async function. The function is
-    given one object as an argument: `{ document, variables, operationName, result }`.
+    given one object as an argument: `{ document, variables, operationName, result, context }`.
 
   * **`validationRules`**: Optional additional validation rules queries must
     satisfy in addition to those defined by the GraphQL spec.
@@ -201,7 +201,7 @@ must return a JSON-serializable Object.
 When called, this is provided an argument which you can use to get information
 about the GraphQL request:
 
-`{ document, variables, operationName, result }`
+`{ document, variables, operationName, result, context }`
 
 This example illustrates adding the amount of time consumed by running the
 provided query, which could perhaps be used by your development tools.
@@ -213,14 +213,18 @@ const app = express();
 
 app.use(session({ secret: 'keyboard cat', cookie: { maxAge: 60000 }}));
 
+const extensions = ({ document, variables, operationName, result, context }) => {
+  return {
+    runTime: Date.now() - context.startTime
+  }
+}
+
 app.use('/graphql', graphqlHTTP(request => {
-  const startTime = Date.now();
   return {
     schema: MyGraphQLSchema,
+    context: { startTime: Date.now() },
     graphiql: true,
-    extensions({ document, variables, operationName, result }) {
-      return { runTime: Date.now() - startTime };
-    }
+    extensions
   };
 }));
 ```

src/__tests__/http-test.js

@@ -1907,16 +1907,24 @@ describe('test harness', () => {
       it('allows for adding extensions', async () => {
         const app = server();
 
+        const extensions = ({ context = {} }) => {
+          if (context !== null && typeof context.startTime === 'number') {
+            return {
+              runTime: 1000000010 /* Date.now() */ - context.startTime,
+            };
+          }
+
+          return {};
+        };
+
         get(
           app,
           urlString(),
           graphqlHTTP(() => {
-            const startTime = 1000000000; /* Date.now(); */
             return {
               schema: TestSchema,
-              extensions() {
-                return { runTime: 1000000010 /* Date.now() */ - startTime };
-              },
+              context: { startTime: 1000000000 },
+              extensions,
             };
           }),
         );

src/index.js

@@ -56,7 +56,7 @@ export type OptionsData = {
   schema: GraphQLSchema,
 
   /**
-   * A value to pass as the context to the graphql() function.
+   * A value to pass as the context to this middleware.
    */
   context?: ?mixed,
 
@@ -131,6 +131,11 @@ export type RequestInfo = {
    * The result of executing the operation.
    */
   result: ?mixed,
+
+  /**
+   * A value to pass as the context to the graphql() function.
+   */
+  context?: ?mixed,
 };
 
 type Middleware = (request: $Request, response: $Response) => Promise<void>;
@@ -148,6 +153,7 @@ function graphqlHTTP(options: Options): Middleware {
   return function graphqlMiddleware(request: $Request, response: $Response) {
     // Higher scoped variables are referred to at various stages in the
     // asynchronous state machine below.
+    let context;
     let params;
     let pretty;
     let formatErrorFn;
@@ -190,11 +196,12 @@ function graphqlHTTP(options: Options): Middleware {
 
         // Collect information from the options data object.
         const schema = optionsData.schema;
-        const context = optionsData.context || request;
         const rootValue = optionsData.rootValue;
         const fieldResolver = optionsData.fieldResolver;
         const graphiql = optionsData.graphiql;
 
+        context = optionsData.context || request;
+
         let validationRules = specifiedRules;
         if (optionsData.validationRules) {
           validationRules = validationRules.concat(optionsData.validationRules);
@@ -297,6 +304,7 @@ function graphqlHTTP(options: Options): Middleware {
               variables,
               operationName,
               result,
+              context,
             }),
           ).then(extensions => {
             if (extensions && typeof extensions === 'object') {