Look in event.path first when selecting endpoint for GraphQL Playgrou…

…nd on Lambda, and check for null (#1527)

* Look in event.path first, and check for null

See here: https://docs.aws.amazon.com/lambda/latest/dg/eventsources.html#eventsources-api-gateway-request

* Add to changelog

CHANGELOG.md

@@ -7,6 +7,7 @@ All of the packages in the `apollo-server` repo are released with the same versi
 - express, koa: remove next after playground [#1436](https://github.com/apollographql/apollo-server/pull/1436)
 - Hapi: Pass the response toolkit to the context function. [#1407](https://github.com/apollographql/apollo-server/pull/1407)
 - update apollo-engine-reporting-protobuf to non-beta [#1429](https://github.com/apollographql/apollo-server/pull/1429)
+- Lambda: Look in event.path first when picking endpoint for GraphQL Playground [#1527](https://github.com/apollographql/apollo-server/pull/1527)
 
 ### rc.10
 

packages/apollo-server-lambda/src/ApolloServer.ts

@@ -119,8 +119,13 @@ export class ApolloServer extends ApolloServerBase {
       if (this.playgroundOptions && event.httpMethod === 'GET') {
         const acceptHeader = event.headers['Accept'] || event.headers['accept'];
         if (acceptHeader && acceptHeader.includes('text/html')) {
+          const path =
+            event.path ||
+            (event.requestContext && event.requestContext.path) ||
+            '/';
+
           const playgroundRenderPageOptions: PlaygroundRenderPageOptions = {
-            endpoint: event.requestContext.path,
+            endpoint: path,
             ...this.playgroundOptions,
           };