Add optional `test` param for custom content handlers (#212)

Add optional `test` param for custom content handlers

This resolves #211.

`multipart/form-data` transmission requires modifying the `Content-Type`
header with a `boundary` section identifier, and as such a custom
content handler would not have previously had access to the running test
case it was working on. This should hopefully be useful for other custom
content handlers in the future.

docs/source/handlers.rst

@@ -107,8 +107,12 @@ handler might accept ``application/x-www-form-urlencoded`` and
 
 If ``accepts`` is defined two additional static methods should be defined:
 
-* ``dumps``: Turn structured Python data from the ``data`` key in a
-  test into a string or byte stream.
+* ``dumps``: Turn structured Python data from the ``data`` key in a test into a
+  string or byte stream. The optional ``test`` param allows you to access the
+  current test case which may help with manipulations for custom content
+  handlers, e.g. ``multipart/form-data`` needs to add a ``boundary`` to the
+  ``Content-Type`` header in order to mark the appropriate sections of the
+  body.
 * ``loads``: Turn a string or byte stream in a response into a Python data
   structure. Gabbi will put this data on the ``response_data``
   attribute on the test, where it can be used in the evaluations

gabbi/case.py

@@ -485,7 +485,7 @@ class HTTPTestCase(testtools.TestCase):
         else:
             dumper_class = self.get_content_handler(content_type)
             if dumper_class:
-                data = dumper_class.dumps(data)
+                data = dumper_class.dumps(data, test=self)
             else:
                 raise ValueError(
                     'unable to process data to %s' % content_type)
@@ -544,7 +544,7 @@ class HTTPTestCase(testtools.TestCase):
                 dumper_class = self.get_content_handler(self.content_type)
                 if dumper_class:
                     full_response = dumper_class.dumps(self.response_data,
-                                                       pretty=True)
+                                                       pretty=True, test=self)
                 else:
                     full_response = self.output
             else:

gabbi/handlers/base.py

@@ -100,7 +100,7 @@ class ContentHandler(ResponseHandler):
         return path
 
     @staticmethod
-    def dumps(data, pretty=False):
+    def dumps(data, pretty=False, test=None):
         """Return structured data as a string.
 
         If pretty is true, prettify.

gabbi/handlers/jsonhandler.py

@@ -44,7 +44,7 @@ class JSONHandler(base.ContentHandler):
         return str(cls.extract_json_path_value(response_data, match))
 
     @staticmethod
-    def dumps(data, pretty=False):
+    def dumps(data, pretty=False, test=None):
         if pretty:
             return json.dumps(data, indent=2, separators=(',', ': '))
         else: