Output 'result' from apollo-link-http error (#755)

Author: skevy

packages/graphql-playground-react/src/state/sessions/fetchingSagas.ts

@@ -237,6 +237,11 @@ export function formatError(error, fetchingSchema: boolean = false) {
 
 function extractMessage(error) {
   if (error instanceof Error) {
+    // Errors from apollo-link-http may include a "result" object, which is a JSON response from
+    // the server. We should surface that to the client
+    if (!!error['result'] && typeof error['result'] === 'object') {
+      return (error as any).result
+    }
     return error.message
   }