fix: emit encoding errors on user stream

src/request.ts

@@ -710,9 +710,16 @@ class DatastoreRequest {
     query = extend(true, new Query(), query);
 
     const makeRequest = (query: Query) => {
-      const reqOpts: RequestOptions = {
-        query: entity.queryToQueryProto(query),
-      };
+      const reqOpts = {} as RequestOptions;
+
+      try {
+        reqOpts.query = entity.queryToQueryProto(query);
+      } catch (e) {
+        // using setImmediate here to make sure this doesn't throw a
+        // synchronous error
+        setImmediate(onResultSet, e);
+        return;
+      }
 
       if (options.consistency) {
         const code = CONSISTENCY_PROTO_CODE[options.consistency.toLowerCase()];

test/request.ts

@@ -819,6 +819,18 @@ describe('Request', () => {
           })
           .emit('reading');
       });
+
+      it('should emit an error when encoding fails', done => {
+        const error = new Error('Encoding error.');
+        sandbox.stub(entity, 'queryToQueryProto').throws(error);
+        request
+          .runQueryStream({})
+          .on('error', (err: Error) => {
+            assert.strictEqual(err, error);
+            done();
+          })
+          .emit('reading');
+      });
     });
 
     describe('success', () => {