contrib.httplib.patch: Don't overwrite return value (#380)

* Add test: enable trace before getting response
* The same situation occurs in ddtrace.api.API._put().
* Don't overwrite return value in finally block

Author: yoichi

ddtrace/contrib/httplib/patch.py

@@ -35,15 +35,13 @@ def _wrap_getresponse(func, instance, args, kwargs):
         try:
             # Get the span attached to this instance, if available
             span = getattr(instance, '_datadog_span', None)
-            if not span:
-                return
+            if span:
+                if resp:
+                    span.set_tag(ext_http.STATUS_CODE, resp.status)
+                    span.error = int(500 <= resp.status)
 
-            if resp:
-                span.set_tag(ext_http.STATUS_CODE, resp.status)
-                span.error = int(500 <= resp.status)
-
-            span.finish()
-            delattr(instance, '_datadog_span')
+                span.finish()
+                delattr(instance, '_datadog_span')
         except Exception:
             log.debug('error applying request tags', exc_info=True)
 

tests/contrib/httplib/test_httplib.py

@@ -320,6 +320,24 @@ def test_httplib_request_get_request_disabled(self):
         spans = self.tracer.writer.pop()
         self.assertEqual(len(spans), 0)
 
+    def test_httplib_request_get_request_disabled_and_enabled(self):
+        """
+        When making a GET request via httplib.HTTPConnection.request
+            when the tracer is disabled
+                we do not capture any spans
+        """
+        self.tracer.enabled = False
+        conn = self.get_http_connection(SOCKET)
+        with contextlib.closing(conn):
+            conn.request('GET', '/status/200')
+            self.tracer.enabled = True
+            resp = conn.getresponse()
+            self.assertEqual(self.to_str(resp.read()), '')
+            self.assertEqual(resp.status, 200)
+
+        spans = self.tracer.writer.pop()
+        self.assertEqual(len(spans), 0)
+
     def test_urllib_request(self):
         """
         When making a request via urllib.request.urlopen