Merge "Handle circular dependencies"

4 files changed, 64 insertions, 1 deletions

diff --git a/keystone/common/dependency.py b/keystone/common/dependency.py
index 3ed261cc..a640031d 100644
--- a/keystone/common/dependency.py
+++ b/keystone/common/dependency.py
@@ -16,6 +16,8 @@
 
 REGISTRY = {}
 
+_future_dependencies = {}
+
 
 class UnresolvableDependencyException(Exception):
     def __init__(self, name):
@@ -32,6 +34,8 @@ def provider(name):
                 init(self, *args, **kwargs)
                 REGISTRY[name] = self
 
+                resolve_future_dependencies(name)
+
             return __wrapped_init__
 
         cls.__init__ = wrapped(cls.__init__)
@@ -48,7 +52,13 @@ def requires(*dependencies):
 
         for dependency in self._dependencies:
             if dependency not in REGISTRY:
-                raise UnresolvableDependencyException(dependency)
+                if dependency in _future_dependencies:
+                    _future_dependencies[dependency] += [self]
+                else:
+                    _future_dependencies[dependency] = [self]
+
+                continue
+
             setattr(self, dependency, REGISTRY[dependency])
 
     def wrapped(cls):
@@ -67,6 +77,26 @@ def requires(*dependencies):
     return wrapped
 
 
+def resolve_future_dependencies(provider_name=None):
+    if provider_name:
+        targets = _future_dependencies.pop(provider_name, [])
+
+        for target in targets:
+            setattr(target, provider_name, REGISTRY[provider_name])
+
+        return
+
+    try:
+        for dependency, targets in _future_dependencies.iteritems():
+            if dependency not in REGISTRY:
+                raise UnresolvableDependencyException(dependency)
+
+            for target in targets:
+                setattr(target, dependency, REGISTRY[dependency])
+    finally:
+        _future_dependencies.clear()
+
+
 def reset():
     """Reset the registry of providers.
 
@@ -75,3 +105,4 @@ def reset():
     """
 
     REGISTRY.clear()
+    _future_dependencies.clear()
diff --git a/keystone/service.py b/keystone/service.py
index 6b0c3708..775dfe5d 100644
--- a/keystone/service.py
+++ b/keystone/service.py
@@ -18,6 +18,7 @@ import routes
 
 from keystone import auth
 from keystone import catalog
+from keystone.common import dependency
 from keystone.common import logging
 from keystone.common import wsgi
 from keystone import config
@@ -44,6 +45,8 @@ DRIVERS = dict(
     trust_api=trust.Manager(),
     token_provider_api=token.provider.Manager())
 
+dependency.resolve_future_dependencies()
+
 
 @logging.fail_gracefully
 def public_app_factory(global_conf, **local_conf):
diff --git a/keystone/test.py b/keystone/test.py
index d06ea4c5..55aca3c6 100644
--- a/keystone/test.py
+++ b/keystone/test.py
@@ -271,6 +271,8 @@ class TestCase(NoModule, unittest.TestCase):
             manager_name = '%s_api' % manager.__name__.split('.')[-1]
             setattr(self, manager_name, manager.Manager())
 
+        dependency.resolve_future_dependencies()
+
     def load_fixtures(self, fixtures):
         """Hacky basic and naive fixture loading based on a python module.
 
diff --git a/tests/test_injection.py b/tests/test_injection.py
index 08ccd7c7..36cd0126 100644
--- a/tests/test_injection.py
+++ b/tests/test_injection.py
@@ -21,6 +21,10 @@ from keystone.common import dependency
 
 
 class TestDependencyInjection(unittest.TestCase):
+    def tearDown(self):
+        dependency.reset()
+        super(TestDependencyInjection, self).tearDown()
+
     def test_dependency_injection(self):
         class Interface(object):
             def do_work(self):
@@ -165,6 +169,29 @@ class TestDependencyInjection(unittest.TestCase):
 
         with self.assertRaises(dependency.UnresolvableDependencyException):
             Consumer()
+            dependency.resolve_future_dependencies()
+
+    def test_circular_dependency(self):
+        p1_name = uuid.uuid4().hex
+        p2_name = uuid.uuid4().hex
+
+        @dependency.provider(p1_name)
+        @dependency.requires(p2_name)
+        class P1(object):
+            pass
+
+        @dependency.provider(p2_name)
+        @dependency.requires(p1_name)
+        class P2(object):
+            pass
+
+        p1 = P1()
+        p2 = P2()
+
+        dependency.resolve_future_dependencies()
+
+        self.assertIs(getattr(p1, p2_name), p2)
+        self.assertIs(getattr(p2, p1_name), p1)
 
     def test_reset(self):
         # Can reset the registry of providers.