feat(lambda): Add support for isBase64Encoded (#4311)

Support AWS Lambda Proxy when `event.isBase64Encoded` is `true` by
decoded from Base64 when that is the case.

CHANGELOG.md

@@ -9,7 +9,7 @@ The version headers in this history reflect the versions of Apollo Server itself
 
 > The changes noted within this `vNEXT` section have not been released yet.  New PRs and commits which introduce changes should include an entry in this `vNEXT` section as part of their development.  With few exceptions, the format of the entry should follow convention (i.e., prefix with package name, use markdown `backtick formatting` for package names and code, suffix with a link to the change-set à la `[PR #YYY](https://link/pull/YYY)`, etc.).  When a release is being prepared, a new header will be (manually) created below and the appropriate changes within that release will be moved into the new section.
 
-- _Nothing yet! Stay tuned!_
+- `apollo-server-lamdbda`: Automatically decode payloads which are Base64-encoded when the `isBase64Encoded` boolean is present on Lambda `event` payloads. [PR #4311](https://github.com/apollographql/apollo-server/pull/4311)
 
 ## v2.15.1
 

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

@@ -32,8 +32,13 @@ export function graphqlLambda(
     callback,
   ): void => {
     context.callbackWaitsForEmptyEventLoop = false;
+    let { body, isBase64Encoded } = event;
 
-    if (event.httpMethod === 'POST' && !event.body) {
+    if (body && isBase64Encoded) {
+      body = Buffer.from(body, 'base64').toString();
+    }
+
+    if (event.httpMethod === 'POST' && !body) {
       return callback(null, {
         body: 'POST body missing.',
         statusCode: 500,
@@ -43,12 +48,12 @@ export function graphqlLambda(
     const contentType = event.headers["content-type"] || event.headers["Content-Type"];
     let query: Record<string, any> | Record<string, any>[];
 
-    if (event.body && event.httpMethod === 'POST' &&
+    if (body && event.httpMethod === 'POST' &&
       contentType && contentType.startsWith("multipart/form-data")
     ) {
-      query = event.body as any;
-    } else if (event.body && event.httpMethod === 'POST') {
-      query = JSON.parse(event.body);
+      query = body as any;
+    } else if (body && event.httpMethod === 'POST') {
+      query = JSON.parse(body);
     } else {
       query = event.queryStringParameters || {};
     }