Improve error reporting for missing nested template

When the template for a TemplateResource was missing from the files dict
and not otherwise available, we provided misleading feedback when
validating the parent template.

First, we log that we are fetching the template from a URL, even though we
would not actually attempt to do so if it is a file:/// URL. Move the log
to after the allowed scheme check, and log debug to indicate when we cannot
find a template file.

While an exception would be generated in
TemplateResource._generate_schema() at resource initialisation time, it is
suppressed and saved for later. An empty template is used to generate the
properties schema. The exception is re-raised when validate() is called,
but during a template validation we only call validate_template(), not
validate(), so the first error we run into will be a mismatch of property
names. (If no property values were passed in the parent template, we may
not even get an error even though we won't be able to create a stack from
the given data.) Also re-raise the stored exception at the beginning of
validate_template() so that users will see the true source of the error.

Change-Id: I1bc100684e1b84fc9ac54ef523d798b317e4dc51
Story: #1739447
Task: 22219

heat/common/urlfetch.py

@@ -39,13 +39,13 @@ def get(url, allowed_schemes=('http', 'https')):
     the allowed_schemes argument.
     Raise an IOError if getting the data fails.
     """
-    LOG.info('Fetching data from %s', url)
-
     components = urllib.parse.urlparse(url)
 
     if components.scheme not in allowed_schemes:
         raise URLFetchError(_('Invalid URL scheme %s') % components.scheme)
 
+    LOG.info('Fetching data from %s', url)
+
     if components.scheme == 'file':
         try:
             return urllib.request.urlopen(url).read()

heat/engine/resources/template_resource.py

@@ -195,6 +195,10 @@ class TemplateResource(stack_resource.StackResource):
         reported_excp = None
         t_data = self.stack.t.files.get(self.template_url)
         stored_t_data = t_data
+
+        if t_data is None:
+            LOG.debug('TemplateResource data file "%s" not found in files.',
+                      self.template_url)
         if not t_data and self.template_url.endswith((".yaml", ".template")):
             try:
                 t_data = self.get_template_file(self.template_url,
@@ -257,9 +261,8 @@ class TemplateResource(stack_resource.StackResource):
                 raise exception.StackValidationFailed(message=msg)
 
     def validate(self):
-        if self.validation_exception is not None:
+        # Calls validate_template()
-            msg = six.text_type(self.validation_exception)
+        result = super(TemplateResource, self).validate()
-            raise exception.StackValidationFailed(message=msg)
 
         try:
             self.template_data()
@@ -280,7 +283,14 @@ class TemplateResource(stack_resource.StackResource):
             facade_cls = fri.get_class(files=self.stack.t.files)
             self._validate_against_facade(facade_cls)
 
-        return super(TemplateResource, self).validate()
+        return result
+
+    def validate_template(self):
+        if self.validation_exception is not None:
+            msg = six.text_type(self.validation_exception)
+            raise exception.StackValidationFailed(message=msg)
+
+        return super(TemplateResource, self).validate_template()
 
     def handle_adopt(self, resource_data=None):
         return self.create_with_template(self.child_template(),

heat_integrationtests/functional/test_template_resource.py

@@ -792,9 +792,11 @@ outputs:
     value:
       not-important
 '''
+        template = yaml.safe_load(self.template)
+        del template['resources']['thisone']['properties']['two']
         try:
             self.stack_create(
-                template=self.template,
+                template=yaml.safe_dump(template),
                 environment=self.env,
                 files={'facade.yaml': self.templ_facade,
                        'concrete.yaml': templ_missing_parameter},