Include exception in custom constraints errors

This refactors constraints to use a shared base class that includes the
error message when validation errors happen.

Co-Authored-By: ala.rezmerita@cloudwatt.com
Closes-Bug: #1297371
Change-Id: Ia382f53d85d83c8c474ad8bda93c6d65f16cfca9

heat/engine/constraints.py

@@ -17,6 +17,7 @@ import re
 
 import six
 
+from heat.engine import clients
 from heat.engine import resources
 
 from heat.common import exception
@@ -508,3 +509,31 @@ class CustomConstraint(Constraint):
         if not constraint:
             return False
         return constraint.validate(value, context)
+
+
+class BaseCustomConstraint(object):
+    """A base class for validation using API clients.
+
+    It will provide a better error message, and reduce a bit of duplication.
+    Subclass must provide `expected_exceptions` and implement
+    `validate_with_client`.
+    """
+    expected_exceptions = ()
+
+    _error_message = None
+
+    def error(self, value):
+        if self._error_message is None:
+            return _("Error validating value %(value)r") % {"value": value}
+        return _("Error validating value %(value)r: %(message)s") % {
+            "value": value, "message": self._error_message}
+
+    def validate(self, value, context):
+        client = clients.Clients(context)
+        try:
+            self.validate_with_client(client, value)
+        except self.expected_exceptions as e:
+            self._error_message = str(e)
+            return False
+        else:
+            return True

heat/engine/resources/image.py

@@ -12,20 +12,17 @@
 #    under the License.
 
 from heat.common import exception
-from heat.engine import clients
 from heat.engine.resources import nova_utils
+from heat.engine import constraints
 
 
-class ImageConstraint(object):
+class ImageConstraint(constraints.BaseCustomConstraint):
 
-    def validate(self, value, context):
-        try:
-            nova_client = clients.Clients(context).nova()
-            nova_utils.get_image_id(nova_client, value)
-        except exception.ImageNotFound:
-            return False
-        else:
-            return True
+    expected_exceptions = (exception.ImageNotFound,)
+
+    def validate_with_client(self, client, value):
+        nova_client = client.nova()
+        nova_utils.get_image_id(nova_client, value)
 
 
 def constraint_mapping():

heat/engine/resources/neutron/net.py

@@ -12,6 +12,7 @@
 #    under the License.
 
 from heat.engine import clients
+from heat.engine import constraints
 from heat.engine import properties
 from heat.engine.resources.neutron import neutron
 
@@ -166,17 +167,14 @@ class Net(neutron.NeutronResource):
                     raise ex
 
 
-class NetworkConstraint(object):
+class NetworkConstraint(constraints.BaseCustomConstraint):
 
-    def validate(self, value, context):
-        try:
-            neutron_client = clients.Clients(context).neutron()
-            neutronV20.find_resourceid_by_name_or_id(
-                neutron_client, 'network', value)
-        except neutron_exp.NeutronClientException:
-            return False
-        else:
-            return True
+    expected_exceptions = (neutron_exp.NeutronClientException,)
+
+    def validate_with_client(self, client, value):
+        neutron_client = client.neutron()
+        neutronV20.find_resourceid_by_name_or_id(
+            neutron_client, 'network', value)
 
 
 def constraint_mapping():

heat/engine/resources/nova_keypair.py

@@ -14,7 +14,7 @@
 from novaclient import exceptions as nova_exceptions
 
 from heat.common import exception
-from heat.engine.clients import Clients
+from heat.engine import constraints
 from heat.engine import properties
 from heat.engine import resource
 from heat.engine.resources import nova_utils
@@ -117,19 +117,17 @@ class KeyPair(resource.Resource):
         return self.resource_id
 
 
-class KeypairConstraint(object):
+class KeypairConstraint(constraints.BaseCustomConstraint):
 
-    def validate(self, value, context):
+    expected_exceptions = (exception.UserKeyPairMissing,)
+
+    def validate_with_client(self, client, value):
         if not value:
             # Don't validate empty key, which can happen when you use a KeyPair
             # resource
             return True
-        try:
-            nova_utils.get_keypair(Clients(context).nova(), value)
-        except exception.UserKeyPairMissing:
-            return False
-        else:
-            return True
+        nova_client = client.nova()
+        nova_utils.get_keypair(nova_client, value)
 
 
 def constraint_mapping():

heat/engine/resources/server.py

@@ -1039,16 +1039,13 @@ class Server(stack_user.StackUser):
         return self._check_active(server)
 
 
-class FlavorConstraint(object):
+class FlavorConstraint(constraints.BaseCustomConstraint):
 
-    def validate(self, value, context):
-        nova_client = clients.Clients(context).nova()
-        try:
-            nova_utils.get_flavor_id(nova_client, value)
-        except exception.FlavorMissing:
-            return False
-        else:
-            return True
+    expected_exceptions = (exception.FlavorMissing,)
+
+    def validate_with_client(self, client, value):
+        nova_client = client.nova()
+        nova_utils.get_flavor_id(nova_client, value)
 
 
 def constraint_mapping():

heat/tests/test_server.py

@@ -292,8 +292,8 @@ class ServersTest(HeatTestCase):
 
         error = self.assertRaises(ValueError, server.handle_create)
         self.assertEqual(
-            'server_create_image_err: image "Slackware" does not '
-            'validate glance.image',
+            'server_create_image_err: image Error validating value '
+            '\'Slackware\': The Image (Slackware) could not be found.',
             str(error))
 
         self.m.VerifyAll()
@@ -343,8 +343,8 @@ class ServersTest(HeatTestCase):
 
         error = self.assertRaises(ValueError, server.handle_create)
         self.assertEqual(
-            'server_create_image_err: image "1" does not '
-            'validate glance.image',
+            'server_create_image_err: image Error validating value \'1\': '
+            'The Image (1) could not be found.',
             str(error))
 
         self.m.VerifyAll()
@@ -816,8 +816,8 @@ class ServersTest(HeatTestCase):
         error = self.assertRaises(exception.StackValidationFailed,
                                   server.validate)
         self.assertEqual(
-            'Property error : server_validate_test: key_name "test2" does '
-            'not validate nova.keypair',
+            'Property error : server_validate_test: key_name Error validating '
+            'value \'test2\': The Key (test2) could not be found.',
             str(error))
         self.m.VerifyAll()