Make requirements checking optional

Commit 3c2b1df85a88162e086d4f62bf99079432851ba8 hard-coded requirements
checking when a plugin is loaded to be turned off (the previous default
was turned on). This commit adds a parameter so the caller can decide.

Change-Id: I639c1fed7231b8adeab1e3ef9c863763a60bfd0d

7 files changed, 75 insertions, 26 deletions

diff --git a/docs/source/history.rst b/docs/source/history.rst
index a7a2958..4993266 100644
--- a/docs/source/history.rst
+++ b/docs/source/history.rst
@@ -4,9 +4,10 @@
 
 dev
 
-- Disable requirements checking when loading plugins. This removes
-  protection against loading the wrong version of a plugin, or that
-  plugin's dependencies.
+- Provide an option to control requirements checking when loading
+  plugins, and disable it by default. This removes protection against
+  loading the wrong version of a plugin, or that plugin's
+  dependencies.
 
 0.13
 
diff --git a/stevedore/dispatch.py b/stevedore/dispatch.py
index 0caa303..226d3ae 100644
--- a/stevedore/dispatch.py
+++ b/stevedore/dispatch.py
@@ -133,13 +133,17 @@ class NameDispatchExtensionManager(DispatchExtensionManager):
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
 
     """
 
     def __init__(self, namespace, check_func, invoke_on_load=False,
                  invoke_args=(), invoke_kwds={},
                  propagate_map_exceptions=False,
-                 on_load_failure_callback=None):
+                 on_load_failure_callback=None,
+                 verify_requirements=False):
         super(NameDispatchExtensionManager, self).__init__(
             namespace=namespace,
             check_func=check_func,
@@ -147,7 +151,8 @@ class NameDispatchExtensionManager(DispatchExtensionManager):
             invoke_args=invoke_args,
             invoke_kwds=invoke_kwds,
             propagate_map_exceptions=propagate_map_exceptions,
-            on_load_failure_callback=on_load_failure_callback
+            on_load_failure_callback=on_load_failure_callback,
+            verify_requirements=verify_requirements,
         )
 
     def _init_plugins(self, extensions):
diff --git a/stevedore/driver.py b/stevedore/driver.py
index a4c0fb0..47273d0 100644
--- a/stevedore/driver.py
+++ b/stevedore/driver.py
@@ -24,24 +24,30 @@ class DriverManager(NamedExtensionManager):
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
     """
 
     def __init__(self, namespace, name,
                  invoke_on_load=False, invoke_args=(), invoke_kwds={},
-                 on_load_failure_callback=None):
+                 on_load_failure_callback=None,
+                 verify_requirements=False):
         super(DriverManager, self).__init__(
             namespace=namespace,
             names=[name],
             invoke_on_load=invoke_on_load,
             invoke_args=invoke_args,
             invoke_kwds=invoke_kwds,
-            on_load_failure_callback=on_load_failure_callback
+            on_load_failure_callback=on_load_failure_callback,
+            verify_requirements=verify_requirements,
         )
 
     @classmethod
     def make_test_instance(cls, extension, namespace='TESTING',
                            propagate_map_exceptions=False,
-                           on_load_failure_callback=None):
+                           on_load_failure_callback=None,
+                           verify_requirements=False):
         """Construct a test DriverManager
 
         Test instances are passed a list of extensions to work from rather
@@ -62,6 +68,9 @@ class DriverManager(NamedExtensionManager):
             an entrypoint fails to load) are (manager, entrypoint,
             exception)
         :type on_load_failure_callback: function
+        :param verify_requirements: Use setuptools to enforce the
+            dependencies of the plugin(s) being loaded. Defaults to False.
+        :type verify_requirements: bool
         :return: The manager instance, initialized for testing
 
         """
@@ -69,7 +78,8 @@ class DriverManager(NamedExtensionManager):
         o = super(DriverManager, cls).make_test_instance(
             [extension], namespace=namespace,
             propagate_map_exceptions=propagate_map_exceptions,
-            on_load_failure_callback=on_load_failure_callback)
+            on_load_failure_callback=on_load_failure_callback,
+            verify_requirements=verify_requirements)
         return o
 
     def _init_plugins(self, extensions):
diff --git a/stevedore/enabled.py b/stevedore/enabled.py
index 0573139..0d228db 100644
--- a/stevedore/enabled.py
+++ b/stevedore/enabled.py
@@ -37,13 +37,17 @@ class EnabledExtensionManager(ExtensionManager):
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
 
     """
 
     def __init__(self, namespace, check_func, invoke_on_load=False,
                  invoke_args=(), invoke_kwds={},
                  propagate_map_exceptions=False,
-                 on_load_failure_callback=None):
+                 on_load_failure_callback=None,
+                 verify_requirements=False,):
         self.check_func = check_func
         super(EnabledExtensionManager, self).__init__(
             namespace,
@@ -51,12 +55,15 @@ class EnabledExtensionManager(ExtensionManager):
             invoke_args=invoke_args,
             invoke_kwds=invoke_kwds,
             propagate_map_exceptions=propagate_map_exceptions,
-            on_load_failure_callback=on_load_failure_callback
+            on_load_failure_callback=on_load_failure_callback,
+            verify_requirements=verify_requirements,
         )
 
-    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds):
+    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds,
+                         verify_requirements):
         ext = super(EnabledExtensionManager, self)._load_one_plugin(
             ep, invoke_on_load, invoke_args, invoke_kwds,
+            verify_requirements,
         )
         if ext and not self.check_func(ext):
             LOG.debug('ignoring extension %r', ep.name)
diff --git a/stevedore/extension.py b/stevedore/extension.py
index 5b79a86..2dd22c7 100644
--- a/stevedore/extension.py
+++ b/stevedore/extension.py
@@ -70,6 +70,9 @@ class ExtensionManager(object):
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
     """
 
     def __init__(self, namespace,
@@ -77,20 +80,23 @@ class ExtensionManager(object):
                  invoke_args=(),
                  invoke_kwds={},
                  propagate_map_exceptions=False,
-                 on_load_failure_callback=None):
+                 on_load_failure_callback=None,
+                 verify_requirements=False):
         self._init_attributes(
             namespace,
             propagate_map_exceptions=propagate_map_exceptions,
             on_load_failure_callback=on_load_failure_callback)
         extensions = self._load_plugins(invoke_on_load,
                                         invoke_args,
-                                        invoke_kwds)
+                                        invoke_kwds,
+                                        verify_requirements)
         self._init_plugins(extensions)
 
     @classmethod
     def make_test_instance(cls, extensions, namespace='TESTING',
                            propagate_map_exceptions=False,
-                           on_load_failure_callback=None):
+                           on_load_failure_callback=None,
+                           verify_requirements=False):
         """Construct a test ExtensionManager
 
         Test instances are passed a list of extensions to work from rather
@@ -111,6 +117,9 @@ class ExtensionManager(object):
             an entrypoint fails to load) are (manager, entrypoint,
             exception)
         :type on_load_failure_callback: function
+        :param verify_requirements: Use setuptools to enforce the
+            dependencies of the plugin(s) being loaded. Defaults to False.
+        :type verify_requirements: bool
         :return: The manager instance, initialized for testing
 
         """
@@ -140,7 +149,8 @@ class ExtensionManager(object):
             self.ENTRY_POINT_CACHE[namespace] = eps
         return self.ENTRY_POINT_CACHE[namespace]
 
-    def _load_plugins(self, invoke_on_load, invoke_args, invoke_kwds):
+    def _load_plugins(self, invoke_on_load, invoke_args, invoke_kwds,
+                      verify_requirements):
         extensions = []
         for ep in self._find_entry_points(self.namespace):
             LOG.debug('found extension %r', ep)
@@ -149,6 +159,7 @@ class ExtensionManager(object):
                                             invoke_on_load,
                                             invoke_args,
                                             invoke_kwds,
+                                            verify_requirements,
                                             )
                 if ext:
                     extensions.append(ext)
@@ -161,10 +172,9 @@ class ExtensionManager(object):
                     self._on_load_failure_callback(self, ep, err)
         return extensions
 
-    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds):
-        # FIXME(dhellmann): This should be optional, controlled
-        # through the args to the constructor for the manager.
-        plugin = ep.load(require=False)
+    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds,
+                         verify_requirements):
+        plugin = ep.load(require=verify_requirements)
         if invoke_on_load:
             obj = plugin(*invoke_args, **invoke_kwds)
         else:
diff --git a/stevedore/hook.py b/stevedore/hook.py
index 334fa60..d2570db 100644
--- a/stevedore/hook.py
+++ b/stevedore/hook.py
@@ -24,18 +24,23 @@ class HookManager(NamedExtensionManager):
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
     """
 
     def __init__(self, namespace, name,
                  invoke_on_load=False, invoke_args=(), invoke_kwds={},
-                 on_load_failure_callback=None):
+                 on_load_failure_callback=None,
+                 verify_requirements=False):
         super(HookManager, self).__init__(
             namespace,
             [name],
             invoke_on_load=invoke_on_load,
             invoke_args=invoke_args,
             invoke_kwds=invoke_kwds,
-            on_load_failure_callback=on_load_failure_callback
+            on_load_failure_callback=on_load_failure_callback,
+            verify_requirements=verify_requirements,
         )
 
     def _init_attributes(self, namespace, names, name_order=False,
diff --git a/stevedore/named.py b/stevedore/named.py
index cf44153..18fe235 100644
--- a/stevedore/named.py
+++ b/stevedore/named.py
@@ -34,26 +34,32 @@ class NamedExtensionManager(ExtensionManager):
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
+    :param verify_requirements: Use setuptools to enforce the
+        dependencies of the plugin(s) being loaded. Defaults to False.
+    :type verify_requirements: bool
 
     """
 
     def __init__(self, namespace, names,
                  invoke_on_load=False, invoke_args=(), invoke_kwds={},
                  name_order=False, propagate_map_exceptions=False,
-                 on_load_failure_callback=None):
+                 on_load_failure_callback=None,
+                 verify_requirements=False):
         self._init_attributes(
             namespace, names, name_order=name_order,
             propagate_map_exceptions=propagate_map_exceptions,
             on_load_failure_callback=on_load_failure_callback)
         extensions = self._load_plugins(invoke_on_load,
                                         invoke_args,
-                                        invoke_kwds)
+                                        invoke_kwds,
+                                        verify_requirements)
         self._init_plugins(extensions)
 
     @classmethod
     def make_test_instance(cls, extensions, namespace='TESTING',
                            propagate_map_exceptions=False,
-                           on_load_failure_callback=None):
+                           on_load_failure_callback=None,
+                           verify_requirements=False):
         """Construct a test NamedExtensionManager
 
         Test instances are passed a list of extensions to use rather than
@@ -74,6 +80,9 @@ class NamedExtensionManager(ExtensionManager):
             an entrypoint fails to load) are (manager, entrypoint,
             exception)
         :type on_load_failure_callback: function
+        :param verify_requirements: Use setuptools to enforce the
+            dependencies of the plugin(s) being loaded. Defaults to False.
+        :type verify_requirements: bool
         :return: The manager instance, initialized for testing
 
         """
@@ -102,7 +111,8 @@ class NamedExtensionManager(ExtensionManager):
         if self._name_order:
             self.extensions = [self[n] for n in self._names]
 
-    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds):
+    def _load_one_plugin(self, ep, invoke_on_load, invoke_args, invoke_kwds,
+                         verify_requirements):
         # Check the name before going any further to prevent
         # undesirable code from being loaded at all if we are not
         # going to use it.
@@ -110,4 +120,5 @@ class NamedExtensionManager(ExtensionManager):
             return None
         return super(NamedExtensionManager, self)._load_one_plugin(
             ep, invoke_on_load, invoke_args, invoke_kwds,
+            verify_requirements,
         )