Made all tracker methods chainable

- closes snowplow#105

Author: fblundun

CHANGES.txt

@@ -8,6 +8,8 @@ Started setting and sending eid (#93)
 Allowed a single Tracker instance to send events to multiple Emitters (#91)
 Started passing a list of dictionaries to the on_failure callback for POST requests (#104)
 Made the "name" argument of track_screen_view optional (#103)
+Made all tracker methods chainable (#105)
+Stopped sending empty payloads (#106) (TODO)
 
 Version 0.4.0 (2014-06-10)
 --------------------------

snowplow_tracker/emitters.py

@@ -139,7 +139,7 @@ def input(self, payload):
             self.buffer.append(payload)
 
         if len(self.buffer) >= self.buffer_size:
-            return self.flush()
+            self.flush()
 
     @task(name="Flush")
     def flush(self):
@@ -151,14 +151,13 @@ def flush(self):
                 "schema": PAYLOAD_DATA_SCHEMA,
                 "data": self.buffer
             })
-            buffer_length = len(self.buffer)
+            temp_buffer = self.buffer
             self.buffer = []
             status_code = self.http_post(data).status_code
             if status_code == 200 and self.on_success is not None:
                 self.on_success(len(temp_buffer))
             elif self.on_failure is not None:
                 self.on_failure(0, temp_buffer)
-            return status_code
 
         elif self.method == "get":
             success_count = 0
@@ -180,8 +179,6 @@ def flush(self):
             elif self.on_failure is not None:
                 self.on_failure(success_count, unsent_requests)
 
-            return status_code
-
         else:
             logger.warn(self.method + ' is not a recognised HTTP method. Use "get" or "post".')
 
@@ -216,8 +213,7 @@ def sync_flush(self):
         result = Emitter.flush(self)
         for t in self.threads:
             t.join(THREAD_TIMEOUT)
-        logger.debug("Finished synchrous flush")
-        return result
+        logger.info("Finished synchrous flush")
 
 
 class AsyncEmitter(Emitter):

snowplow_tracker/tracker.py

@@ -123,14 +123,11 @@ def track(self, pb):
 
             :param  pb:              Payload builder
             :type   pb:              payload
-            :rtype:                  tracker | list(int)
+            :rtype:                  tracker
         """
-        results = [emitter.input(pb.nv_pairs) for emitter in self.emitters]
-        filtered = [res for res in results if res is not None]
-        if filtered:
-            return filtered
-        else:
-            return self
+        for emitter in self.emitters:
+            emitter.input(pb.nv_pairs)
+        return self
 
     @contract
     def complete_payload(self, pb, context, tstamp):
@@ -144,7 +141,7 @@ def complete_payload(self, pb, context, tstamp):
             :type   context:         list(dict(string:*)) | None
             :param  tstamp:          Optional user-provided timestamp for the event
             :type   tstamp:          int | float | None
-            :rtype:                  tracker | list(int)
+            :rtype:                  tracker
         """
         pb.add("eid", Tracker.get_uuid())
         pb.add("dtm", Tracker.get_timestamp(tstamp))
@@ -169,7 +166,7 @@ def track_page_view(self, page_url, page_title=None, referrer=None, context=None
             :type   referrer:       string_or_none
             :param  context:        Custom context for the event
             :type   context:        list(dict(string:*)) | None
-            :rtype:                 tracker | list(int)
+            :rtype:                 tracker
         """
         pb = payload.Payload()
         pb.add("e", "pv")           # pv: page view
@@ -204,7 +201,7 @@ def track_ecommerce_transaction_item(self, order_id, sku, price, quantity,
             :type   currency:    string_or_none
             :param  context:     Custom context for the event
             :type   context:     list(dict(string:*)) | None
-            :rtype:              tracker | list(int)
+            :rtype:              tracker
         """
         pb = payload.Payload()
         pb.add("e", "ti")
@@ -247,7 +244,7 @@ def track_ecommerce_transaction(self, order_id, total_value,
             :type   items:          list(dict(str:*))
             :param  context:        Custom context for the event
             :type   context:        list(dict(string:*)) | None
-            :rtype:                 tracker | dict(string:*)
+            :rtype:                 tracker
         """
         pb = payload.Payload()
         pb.add("e", "tr")
@@ -273,10 +270,7 @@ def track_ecommerce_transaction(self, order_id, total_value,
             item["currency"] = currency
             item_results.append(self.track_ecommerce_transaction_item(**item))
 
-        if not isinstance(transaction_result, Tracker):
-            return {"transaction_result": transaction_result, "item_results": item_results}
-        else:
-            return self
+        return self
 
     @contract
     def track_screen_view(self, name=None, id_=None, context=None, tstamp=None):
@@ -287,7 +281,7 @@ def track_screen_view(self, name=None, id_=None, context=None, tstamp=None):
             :type   id_:            string_or_none
             :param  context:        Custom context for the event
             :type   context:        list(dict(string:*)) | None
-            :rtype:                 tracker | list(int)
+            :rtype:                 tracker
         """
         screen_view_properties = {}
         if name is not None:
@@ -320,7 +314,7 @@ def track_struct_event(self, category, action, label=None, property_=None, value
             :type   value:          int | float | None
             :param  context:        Custom context for the event
             :type   context:        list(dict(string:*)) | None
-            :rtype:                 tracker | list(int)
+            :rtype:                 tracker
         """
         pb = payload.Payload()
         pb.add("e", "se")
@@ -342,7 +336,7 @@ def track_unstruct_event(self, event_json, context=None, tstamp=None):
             :type   event_json:      dict(string: string | dict)
             :param  context:         Custom context for the event
             :type   context:         list(dict(string:*)) | None
-            :rtype:                  tracker | list(int)
+            :rtype:                  tracker
         """
 
         envelope = {"schema": UNSTRUCT_EVENT_SCHEMA , "data": event_json}
@@ -361,15 +355,14 @@ def flush(self, async=False):
 
             :param  async:  Whether the flush is done asynchronously. Default is False
             :type   async:  bool
-            :rtype:         tracker | list(int)
+            :rtype:         tracker
         """
-        if async:
-            for e in self.emitters:
-                e.flush()
-            return self
-        else:
-            results = [emitter.sync_flush() for emitter in self.emitters]
-            return [r for r in results if r is not None]
+        for emitter in self.emitters:
+            if async:
+                emitter.flush()
+            else:
+                emitter.sync_flush()
+        return self
 
     @contract
     def set_subject(self, subject):