Support custom authentication handlers for private pypi.

news/4475.feature

@@ -0,0 +1 @@
+Support for custom authentication handlers via --auth-plugin option.

src/pip/_internal/cli/cmdoptions.py

@@ -21,6 +21,8 @@
 from optparse import SUPPRESS_HELP, Option, OptionGroup
 from textwrap import dedent
 
+from pip._vendor.pkg_resources import iter_entry_points
+
 from pip._internal.cli.progress_bars import BAR_TYPES
 from pip._internal.exceptions import CommandError
 from pip._internal.locations import USER_CACHE_DIR, get_src_prefix
@@ -920,6 +922,35 @@ def check_list_path_option(options):
 )  # type: Callable[..., Option]
 
 
+discovered_auth_plugins = {
+    entry_point.name: entry_point
+    for entry_point
+    in iter_entry_points('pip.auth_plugins')
+}
+
+
+def _handle_auth_plugin(option, opt_str, value, parser):
+    # type: (Option, str, str, OptionParser) -> None
+    plugin = discovered_auth_plugins[value].load()
+    setattr(parser.values, option.dest, plugin.Auth)
+
+
+auth_plugin = partial(
+    PipOption,
+    '--auth', '--auth-plugin',
+    dest='auth_class',
+    type='choice',
+    metavar='plugin',
+    default=None,
+    choices=list(discovered_auth_plugins.keys()),
+    action='callback',
+    callback=_handle_auth_plugin,
+    help='Specify authentication plugin to be used: {}.'.format(
+        ', '.join(discovered_auth_plugins.keys()) or 'no plugins found'
+    ),
+)  # type: Callable[..., Option]
+
+
 ##########
 # groups #
 ##########
@@ -948,6 +979,7 @@ def check_list_path_option(options):
         no_color,
         no_python_version_warning,
         unstable_feature,
+        auth_plugin,
     ]
 }  # type: Dict[str, Any]
 

src/pip/_internal/cli/req_command.py

@@ -97,6 +97,7 @@ def _build_session(self, options, retries=None, timeout=None):
             retries=retries if retries is not None else options.retries,
             trusted_hosts=options.trusted_hosts,
             index_urls=self._get_index_urls(options),
+            auth_class=options.auth_class,
         )
 
         # Handle custom ca-bundles from the user

src/pip/_internal/network/session.py

@@ -238,6 +238,9 @@ def __init__(self, *args, **kwargs):
         cache = kwargs.pop("cache", None)
         trusted_hosts = kwargs.pop("trusted_hosts", [])  # type: List[str]
         index_urls = kwargs.pop("index_urls", None)
+        auth_class = kwargs.pop("auth_class", None)
+        if auth_class is None:
+            auth_class = MultiDomainBasicAuth
 
         super(PipSession, self).__init__(*args, **kwargs)
 
@@ -249,7 +252,7 @@ def __init__(self, *args, **kwargs):
         self.headers["User-Agent"] = user_agent()
 
         # Attach our Authentication handler to the session
-        self.auth = MultiDomainBasicAuth(index_urls=index_urls)
+        self.auth = auth_class(index_urls=index_urls)
 
         # Create our urllib3.Retry instance which will allow us to customize
         # how we handle retries.