Pass service_name to process_errors

Previously on Buffy... The process_errors was parsing a load of
ValidationErrors that we get back from jsonschema which included
assumptions about the state of the instance we're validating.

Now it's split in two and we're doing field separate to service,
those assumptions don't hold and we can't logically retrieve the
service_name from the error parsing when we're doing service schema
validation, have to explicitly pass this in.

process_errors is high on my list for some future re-factoring to help
make it a bit clearer, smaller state of doing things.

Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>

compose/config/config.py

@@ -184,7 +184,7 @@ class ServiceLoader(object):
             self.service_dict = self.resolve_extends()
 
         if not self.already_seen:
-            validate_against_service_schema(self.service_dict)
+            validate_against_service_schema(self.service_dict, self.service_name)
 
         return process_container_options(self.service_dict, working_dir=self.working_dir)
 

compose/config/validation.py

@@ -95,7 +95,7 @@ def get_unsupported_config_msg(service_name, error_key):
     return msg
 
 
-def process_errors(errors):
+def process_errors(errors, service_name=None):
     """
     jsonschema gives us an error tree full of information to explain what has
     gone wrong. Process each error and pull out relevant information and re-write
@@ -137,13 +137,14 @@ def process_errors(errors):
                 root_msgs.append(_clean_error_message(error.message))
 
         else:
-            try:
+            if not service_name:
                 # field_schema errors will have service name on the path
                 service_name = error.path[0]
                 error.path.popleft()
-            except IndexError:
-                # service_schema errors will have the name in the instance
-                service_name = error.instance.get('name')
+            else:
+                # service_schema errors have the service name passed in, as that
+                # is not available on error.path or necessarily error.instance
+                service_name = service_name
 
             if error.validator == 'additionalProperties':
                 invalid_config_key = _parse_key_from_error_msg(error)
@@ -218,12 +219,12 @@ def validate_against_fields_schema(config):
     return _validate_against_schema(config, schema_filename)
 
 
-def validate_against_service_schema(config):
+def validate_against_service_schema(config, service_name):
     schema_filename = "service_schema.json"
-    return _validate_against_schema(config, schema_filename)
+    return _validate_against_schema(config, schema_filename, service_name)
 
 
-def _validate_against_schema(config, schema_filename):
+def _validate_against_schema(config, schema_filename, service_name=None):
     config_source_dir = os.path.dirname(os.path.abspath(__file__))
     schema_file = os.path.join(config_source_dir, schema_filename)
 
@@ -235,5 +236,5 @@ def _validate_against_schema(config, schema_filename):
 
     errors = [error for error in sorted(validation_output.iter_errors(config), key=str)]
     if errors:
-        error_msg = process_errors(errors)
+        error_msg = process_errors(errors, service_name)
         raise ConfigurationError("Validation failed, reason(s):\n{}".format(error_msg))