fix: maxBytes batching sending empty messages (#281)

src/publisher.js

@@ -163,15 +163,18 @@ class Publisher {
     const opts = this.settings.batching;
     // if this message puts us over the maxBytes option, then let's ship
     // what we have and add it to the next batch
-    if (this.inventory_.bytes + data.length > opts.maxBytes) {
+    if (
+      this.inventory_.bytes > 0 &&
+      this.inventory_.bytes + data.length > opts.maxBytes
+    ) {
       this.publish_();
     }
     // add it to the queue!
     this.queue_(data, attributes, callback);
     // next lets check if this message brings us to the message cap or if we
-    // magically hit the max byte limit
+    // hit the max byte limit
     const hasMaxMessages = this.inventory_.queued.length === opts.maxMessages;
-    if (this.inventory_.bytes === opts.maxBytes || hasMaxMessages) {
+    if (this.inventory_.bytes >= opts.maxBytes || hasMaxMessages) {
       this.publish_();
       return;
     }

test/publisher.js

@@ -210,6 +210,32 @@ All attributes must be in the form of a string.
       publisher.publish(DATA, done);
     });
 
+    it('should not attempt to publish empty payload if data puts payload above size cap', function(done) {
+      const pushRequests = [];
+      publisher.settings.batching.maxBytes = 2;
+      publisher.inventory_.bytes = 0;
+
+      publisher.publish_ = function() {
+        assert.notStrictEqual(publisher.inventory_.queued.length, 0);
+        pushRequests.push(publisher.inventory_.queued);
+        publisher.inventory_.callbacks.forEach(function(callback) {
+          callback();
+        });
+      };
+
+      publisher.publish(DATA, function() {
+        assert.deepStrictEqual(pushRequests, [
+          [
+            {
+              data: DATA,
+              attributes: {},
+            },
+          ],
+        ]);
+        done();
+      });
+    });
+
     it('should publish if data puts payload at size cap', function(done) {
       publisher.queue_ = function() {
         publisher.inventory_.bytes += DATA.length;