Added support for transport adapter plugins

#276, #298

httpie/plugins/__init__.py

@@ -1,4 +1,12 @@
-from httpie.plugins.base import AuthPlugin, FormatterPlugin, ConverterPlugin
+"""
+WARNING: The plugin API is still work in progress and will
+         probably be completely reworked by v1.0.0.
+
+"""
+from httpie.plugins.base import (
+    AuthPlugin, FormatterPlugin,
+    ConverterPlugin, TransportPlugin
+)
 from httpie.plugins.manager import PluginManager
 from httpie.plugins.builtin import BasicAuthPlugin, DigestAuthPlugin
 from httpie.output.formatters.headers import HeadersFormatter

httpie/plugins/base.py

@@ -15,7 +15,7 @@ class AuthPlugin(BasePlugin):
     """
     Base auth plugin class.
 
-    See <https://github.com/jkbr/httpie-ntlm> for an example auth plugin.
+    See <https://github.com/jakubroztocil/httpie-ntlm> for an example auth plugin.
 
     """
     # The value that should be passed to --auth-type
@@ -30,6 +30,25 @@ class AuthPlugin(BasePlugin):
         raise NotImplementedError()
 
 
+class TransportPlugin(BasePlugin):
+    """
+
+    http://docs.python-requests.org/en/latest/user/advanced/#transport-adapters
+
+    """
+
+    # The URL prefix the adapter should be mount to.
+    prefix = None
+
+    def get_adapter(self):
+        """
+        Return a ``requests.adapters.BaseAdapter`` subclass instance to be
+        mounted to ``self.prefix``.
+
+        """
+        raise NotImplementedError()
+
+
 class ConverterPlugin(object):
 
     def __init__(self, mime):

httpie/plugins/manager.py

@@ -1,12 +1,14 @@
 from itertools import groupby
 from pkg_resources import iter_entry_points
 from httpie.plugins import AuthPlugin, FormatterPlugin, ConverterPlugin
+from httpie.plugins.base import TransportPlugin
 
 
 ENTRY_POINT_NAMES = [
     'httpie.plugins.auth.v1',
     'httpie.plugins.formatter.v1',
     'httpie.plugins.converter.v1',
+    'httpie.plugins.transport.v1',
 ]
 
 
@@ -56,3 +58,8 @@ class PluginManager(object):
     def get_converters(self):
         return [plugin for plugin in self
                 if issubclass(plugin, ConverterPlugin)]
+
+    # Adapters
+    def get_adapter_plugins(self):
+        return [plugin for plugin in self
+                if issubclass(plugin, TransportPlugin)]