Refactor validators into a list, and add a custom validator function, which is passed the YAML as an argument, and will return (rv,msgs) to signal custom semantic validation results

config/__init__.py

@@ -69,6 +69,13 @@ class Validator(object):
         self.logger.addHandler(logging.NullHandler())
 
         self.schema = schema
+        self.validators = [
+           validate_bondethernets,
+           validate_interfaces,
+           validate_loopbacks,
+           validate_bridgedomains,
+           validate_vxlan_tunnels,
+           validate_taps ]
 
     def validate(self, yaml):
         ret_rv = True
@@ -107,41 +114,12 @@ class Validator(object):
 
         self.logger.debug("Validating Semantics...")
 
-        rv, msgs = validate_bondethernets(yaml)
+        for v in self.validators:
-        if msgs:
+            rv, msgs = v(yaml)
-            ret_msgs.extend(msgs)
+            if msgs:
-        if not rv:
+                ret_msgs.extend(msgs)
-            ret_rv = False
+            if not rv:
-
+                ret_rv = False
-        rv, msgs = validate_interfaces(yaml)
-        if msgs:
-            ret_msgs.extend(msgs)
-        if not rv:
-            ret_rv = False
-
-        rv, msgs = validate_loopbacks(yaml)
-        if msgs:
-            ret_msgs.extend(msgs)
-        if not rv:
-            ret_rv = False
-
-        rv, msgs = validate_bridgedomains(yaml)
-        if msgs:
-            ret_msgs.extend(msgs)
-        if not rv:
-            ret_rv = False
-
-        rv, msgs = validate_vxlan_tunnels(yaml)
-        if msgs:
-            ret_msgs.extend(msgs)
-        if not rv:
-            ret_rv = False
-
-        rv, msgs = validate_taps(yaml)
-        if msgs:
-            ret_msgs.extend(msgs)
-        if not rv:
-            ret_rv = False
 
         if ret_rv:
             self.logger.debug("Semantics correctly validated")
@@ -162,3 +140,11 @@ class Validator(object):
 
         self.logger.info("Configuration validated successfully")
         return True
+
+    def add_validator(self, func):
+        """ Add a validator function, which strictly takes the prototype
+               rv, msgs = func(yaml)
+            returning a Boolean success value in rv and a List of strings
+            in msgs. The function will be passed the configuration YAML and
+            gets to opine if it's valid or not. """
+        self.validators.append(func)

tests.py

@@ -27,6 +27,14 @@ except ImportError:
     print("ERROR: install argparse manually: sudo pip install argparse")
     sys.exit(-2)
 
+def example_validator(yaml):
+    """ A simple example validator that takes the YAML configuration file as an input,
+    and returns a tuple of rv (return value, True is success), and a list of string
+    messages to the validation framework. """
+    rv = True
+    msgs = []
+
+    return rv, msgs
 
 class YAMLTest(unittest.TestCase):
     def __init__(self, testName, yaml_filename, yaml_schema):