Define resource/output definition sections with constants

It was unclear what the valid arguments to Template.get_section_name() were
(especially since the function is mis-named for what it actually does in
HOT). Define the arguments as constants and don't pass string literals any
more. Be consistent in how we define paths, standardising on the method in
Resource.validate_template().

Change-Id: Ifd073d9889ff60502f78aaa54532cec2b7814d93

heat/engine/output.py

@@ -19,6 +19,15 @@ from heat.common import exception
 from heat.engine import function
 
 
+# Field names that can be passed to Template.get_section_name() in order to
+# determine the appropriate name for a particular template format.
+FIELDS = (
+    VALUE, DESCRIPTION,
+) = (
+    'Value', 'Description',
+)
+
+
 class OutputDefinition(object):
     """A definition of a stack output, independent of any template format."""
 
@@ -30,9 +39,9 @@ class OutputDefinition(object):
         self._deps = None
         self._all_dep_attrs = None
 
-    def validate(self, path=''):
+    def validate(self):
         """Validate the output value without resolving it."""
-        function.validate(self._value, path)
+        function.validate(self._value, VALUE)
 
     def required_resource_names(self):
         if self._deps is None:

heat/engine/resources/openstack/sahara/job_binary.py

@@ -18,6 +18,7 @@ from heat.common import exception
 from heat.common.i18n import _
 from heat.engine import properties
 from heat.engine import resource
+from heat.engine import rsrc_defn
 from heat.engine import support
 
 
@@ -105,8 +106,8 @@ class JobBinary(resource.Resource):
                 and uuidutils.is_uuid_like(url[len("internal-db://"):]))):
             msg = _("%s is not a valid job location.") % url
             raise exception.StackValidationFailed(
-                path=[self.stack.t.get_section_name('resources'), self.name,
-                      self.stack.t.get_section_name('properties')],
+                path=[self.stack.t.RESOURCES, self.name,
+                      self.stack.t.get_section_name(rsrc_defn.PROPERTIES)],
                 message=msg)
 
     def handle_create(self):

heat/engine/resources/openstack/sahara/templates.py

@@ -24,6 +24,7 @@ from heat.common.i18n import _
 from heat.engine import constraints
 from heat.engine import properties
 from heat.engine import resource
+from heat.engine import rsrc_defn
 from heat.engine import support
 from heat.engine import translation
 
@@ -346,9 +347,9 @@ class SaharaNodeGroupTemplate(resource.Resource):
                     'unsupported': ', '.join(unsupported_processes),
                     'allowed': ', '.join(allowed_processes)})
             raise exception.StackValidationFailed(
-                path=[self.stack.t.get_section_name('resources'),
+                path=[self.stack.t.RESOURCES,
                       self.name,
-                      self.stack.t.get_section_name('properties')],
+                      self.stack.t.get_section_name(rsrc_defn.PROPERTIES)],
                 message=msg)
 
     def parse_live_resource_data(self, resource_properties, resource_data):

heat/engine/rsrc_defn.py

@@ -26,6 +26,17 @@ from heat.engine import properties
 __all__ = ['ResourceDefinition']
 
 
+# Field names that can be passed to Template.get_section_name() in order to
+# determine the appropriate name for a particular template format.
+FIELDS = (
+    TYPE, PROPERTIES, METADATA, DELETION_POLICY, UPDATE_POLICY,
+    DEPENDS_ON, DESCRIPTION, EXTERNAL_ID,
+) = (
+    'Type', 'Properties', 'Metadata', 'DeletionPolicy', 'UpdatePolicy',
+    'DependsOn', 'Description', 'external_id',
+)
+
+
 @repr_wrapper
 class ResourceDefinition(object):
     """A definition of a resource, independent of any template format."""
@@ -230,9 +241,9 @@ class ResourceDefinition(object):
                 return '.'.join([self.name, section])
 
             prop_deps = function.dependencies(self._properties,
-                                              path('Properties'))
+                                              path(PROPERTIES))
             metadata_deps = function.dependencies(self._metadata,
-                                                  path('Metadata'))
+                                                  path(METADATA))
             implicit_depends = six.moves.map(lambda rp: rp.name,
                                              itertools.chain(prop_deps,
                                                              metadata_deps))
@@ -282,7 +293,7 @@ class ResourceDefinition(object):
         """
         props = properties.Properties(schema, self._properties or {},
                                       function.resolve, context=context,
-                                      section='Properties')
+                                      section=PROPERTIES)
         props.update_translation(self._rules, self._client_resolve)
         return props
 
@@ -301,7 +312,7 @@ class ResourceDefinition(object):
         """
         props = properties.Properties(schema, self._update_policy or {},
                                       function.resolve, context=context,
-                                      section='UpdatePolicy')
+                                      section=UPDATE_POLICY)
         props.update_translation(self._rules, self._client_resolve)
         return props
 

heat/engine/stack.py

@@ -904,13 +904,15 @@ class Stack(collections.Mapping):
 
         for op_name, output in six.iteritems(self.outputs):
             try:
-                path = '.'.join([self.t.OUTPUTS, op_name,
-                                 self.t.OUTPUT_VALUE])
-                output.validate(path)
-            except exception.StackValidationFailed:
-                raise
-            except AssertionError:
-                raise
+                output.validate()
+            except exception.StackValidationFailed as ex:
+                path = [self.t.OUTPUTS, op_name,
+                        self.t.get_section_name(ex.path[0])]
+                path.extend(ex.path[1:])
+                raise exception.StackValidationFailed(
+                    error=ex.error,
+                    path=path,
+                    message=ex.error_message)
 
     def requires_deferred_auth(self):
         """Determine whether to perform API requests with deferred auth.

heat/engine/template.py

@@ -213,7 +213,16 @@ class Template(collections.Mapping):
 
     @abc.abstractmethod
     def get_section_name(self, section):
-        """Return a correct section name."""
+        """Get the name of a field within a resource or output definition.
+
+        Return the name of the given field (specified by the constants given
+        in heat.engine.rsrc_defn and heat.engine.output) in the template
+        format. This is used in error reporting to help users find the
+        location of errors in the template.
+
+        Note that 'section' here does not refer to a top-level section of the
+        template (like parameters, resources, &c.) as it does everywhere else.
+        """
         pass
 
     @abc.abstractmethod