Handles null in structured logging (Fixes #716) (#717)

Author: mbleigh

spec/logger.spec.ts

@@ -65,6 +65,15 @@ describe(`logger (${
       });
       sandbox.restore(); // to avoid swallowing test runner output
     });
+
+    it('should not recognize null as a structured logging object', () => {
+      logger.log('hello', 'world', null);
+      expectStdout({
+        severity: 'INFO',
+        message: 'hello world null',
+      });
+      sandbox.restore(); // to avoid swallowing test runner output
+    });
   });
 
   describe('write', () => {

src/logger.ts

@@ -104,7 +104,7 @@ export function error(...args: any[]) {
 function entryFromArgs(severity: LogSeverity, args: any[]): LogEntry {
   let entry = {};
   const lastArg = args[args.length - 1];
-  if (typeof lastArg == 'object' && lastArg.constructor == Object) {
+  if (lastArg && typeof lastArg == 'object' && lastArg.constructor == Object) {
     entry = args.pop();
   }
   return Object.assign({}, entry, {