Versioned Endpoint hack for Sessions

To maintain compatibility we must allow people to specify a versioned
URL in the service catalog but allow the plugins to return a different
URL to users.

We need this to be a general approach as other services will likely have
a similar problem with their catalog.

The expectation here is that a client will register the catalog hack at
import time rather than for every request.

Closes-Bug: #1335726
Change-Id: I244f0ec3acca39fd1b2a2c5883abc06ec10eddc7

1 files changed, 31 insertions, 0 deletions

diff --git a/keystoneclient/discover.py b/keystoneclient/discover.py
index 07de97d..982683a 100644
--- a/keystoneclient/discover.py
+++ b/keystoneclient/discover.py
@@ -266,3 +266,34 @@ class Discover(_discover.Discover):
         """
         version_data = self._calculate_version(version, unstable)
         return self._create_client(version_data, **kwargs)
+
+
+def add_catalog_discover_hack(service_type, old, new):
+    """Adds a version removal rule for a particular service.
+
+    Originally deployments of OpenStack would contain a versioned endpoint in
+    the catalog for different services. E.g. an identity service might look
+    like ``http://localhost:5000/v2.0``. This is a problem when we want to use
+    a different version like v3.0 as there is no way to tell where it is
+    located. We cannot simply change all service catalogs either so there must
+    be a way to handle the older style of catalog.
+
+    This function adds a rule for a given service type that if part of the URL
+    matches a given regular expression in *old* then it will be replaced with
+    the *new* value. This will replace all instances of old with new. It should
+    therefore contain a regex anchor.
+
+    For example the included rule states::
+
+        add_catalog_version_hack('identity', re.compile('/v2.0/?$'), '/')
+
+    so if the catalog retrieves an *identity* URL that ends with /v2.0 or
+    /v2.0/ then it should replace it simply with / to fix the user's catalog.
+
+    :param str service_type: The service type as defined in the catalog that
+                             the rule will apply to.
+    :param re.RegexObject old: The regular expression to search for and replace
+                               if found.
+    :param str new: The new string to replace the pattern with.
+    """
+    _discover._VERSION_HACKS.add_discover_hack(service_type, old, new)