ELBv2 modify_rule changes listener rule partially (#1073)

* modify_rule changes listener rule partially

* fix syntax

* fix outdated code

* fix outdated code

moto/elbv2/exceptions.py

@@ -174,3 +174,12 @@ class InvalidTargetGroupNameError(ELBClientError):
         super(InvalidTargetGroupNameError, self).__init__(
             "ValidationError", msg
         )
+
+
+class InvalidModifyRuleArgumentsError(ELBClientError):
+
+    def __init__(self):
+        super(InvalidModifyRuleArgumentsError, self).__init__(
+            "ValidationError",
+            "Either conditions or actions must be specified"
+        )

moto/elbv2/models.py

@@ -23,7 +23,8 @@ from .exceptions import (
     InvalidDescribeRulesRequest,
     RuleNotFoundError,
     DuplicatePriorityError,
-    InvalidTargetGroupNameError
+    InvalidTargetGroupNameError,
+    InvalidModifyRuleArgumentsError
 )
 
 
@@ -429,45 +430,50 @@ class ELBv2Backend(BaseBackend):
         raise ListenerNotFoundError()
 
     def modify_rule(self, rule_arn, conditions, actions):
+        # if conditions or actions is empty list, do not update the attributes
+        if not conditions and not actions:
+            raise InvalidModifyRuleArgumentsError()
         rules = self.describe_rules(listener_arn=None, rule_arns=[rule_arn])
         if not rules:
             raise RuleNotFoundError()
         rule = rules[0]
 
-        # validate conditions
-        for condition in conditions:
-            field = condition['field']
-            if field not in ['path-pattern', 'host-header']:
-                raise InvalidConditionFieldError(field)
+        if conditions:
+            for condition in conditions:
+                field = condition['field']
+                if field not in ['path-pattern', 'host-header']:
+                    raise InvalidConditionFieldError(field)
 
-            values = condition['values']
-            if len(values) == 0:
-                raise InvalidConditionValueError('A condition value must be specified')
-            if len(values) > 1:
-                raise InvalidConditionValueError(
-                    "The '%s' field contains too many values; the limit is '1'" % field
-                )
-
-            # TODO: check pattern of value for 'host-header'
-            # TODO: check pattern of value for 'path-pattern'
+                values = condition['values']
+                if len(values) == 0:
+                    raise InvalidConditionValueError('A condition value must be specified')
+                if len(values) > 1:
+                    raise InvalidConditionValueError(
+                        "The '%s' field contains too many values; the limit is '1'" % field
+                    )
+                # TODO: check pattern of value for 'host-header'
+                # TODO: check pattern of value for 'path-pattern'
 
         # validate Actions
         target_group_arns = [target_group.arn for target_group in self.target_groups.values()]
-        for i, action in enumerate(actions):
-            index = i + 1
-            action_type = action['type']
-            if action_type not in ['forward']:
-                raise InvalidActionTypeError(action_type, index)
-            action_target_group_arn = action['target_group_arn']
-            if action_target_group_arn not in target_group_arns:
-                raise ActionTargetGroupNotFoundError(action_target_group_arn)
+        if actions:
+            for i, action in enumerate(actions):
+                index = i + 1
+                action_type = action['type']
+                if action_type not in ['forward']:
+                    raise InvalidActionTypeError(action_type, index)
+                action_target_group_arn = action['target_group_arn']
+                if action_target_group_arn not in target_group_arns:
+                    raise ActionTargetGroupNotFoundError(action_target_group_arn)
 
         # TODO: check for error 'TooManyRegistrationsForTargetId'
         # TODO: check for error 'TooManyRules'
 
         # modify rule
-        rule.conditions = conditions
-        rule.actions = actions
+        if conditions:
+            rule.conditions = conditions
+        if actions:
+            rule.actions = actions
         return [rule]
 
     def register_targets(self, target_group_arn, instances):

tests/test_elbv2/test_elbv2.py

@@ -731,7 +731,7 @@ def test_handle_listener_rules():
             RuleArns=[first_rule['RuleArn']]
         )
 
-    # modify rule
+    # modify rule partially
     new_host = 'new.example.com'
     new_path_pattern = 'new_path'
     modified_rule = conn.modify_rule(
@@ -743,15 +743,15 @@ def test_handle_listener_rules():
             {
                 'Field': 'path-pattern',
                 'Values': [ new_path_pattern ]
-            }],
-            Actions=[{
-                'TargetGroupArn': target_group.get('TargetGroupArn'),
-                'Type': 'forward'
             }]
-
     )['Rules'][0]
+
     rules = conn.describe_rules(ListenerArn=http_listener_arn)
-    modified_rule.should.equal(rules['Rules'][0])
+    obtained_rule = rules['Rules'][0]
+    modified_rule.should.equal(obtained_rule)
+    obtained_rule['Conditions'][0]['Values'][0].should.equal(new_host)
+    obtained_rule['Conditions'][1]['Values'][0].should.equal(new_path_pattern)
+    obtained_rule['Actions'][0]['TargetGroupArn'].should.equal(target_group.get('TargetGroupArn'))
 
     # modify priority
     conn.set_rule_priorities(