Add MVP rule for AWS::Events::Rule ScheduleExpression

docs/rules.md

@@ -44,7 +44,7 @@ To include these rules, use the `-e/include-experimental` argument when running
 
 
 ## Rules
-The following **119** rules are applied by this linter:
+The following **120** rules are applied by this linter:
 (_This documentation is generated from the Rules, do not alter this manually_)
 
 | Rule ID  | Title | Description | Config<br />(Name:Type:Default) | Source | Tags |
@@ -117,6 +117,7 @@ The following **119** rules are applied by this linter:
 | E3024<a name="E3024"></a> | Validate that ProvisionedThroughput is not specified with BillingMode PAY_PER_REQUEST | When using ProvisionedThroughput with BillingMode PAY_PER_REQUEST will result in BillingMode being changed to PROVISIONED |  | [Source](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-dynamodb-table.html) | `resources`,`dynamodb`,`provisioned_throughput`,`billing_mode` |
 | E3025<a name="E3025"></a> | RDS instance type is compatible with the RDS type | Check the RDS instance types are supported by the type of RDS engine. Only if the values are strings will this be checked. |  | [Source](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.DBInstanceClass.html) | `resources`,`rds` |
 | E3026<a name="E3026"></a> | Check Elastic Cache Redis Cluster settings | Evaluate Redis Cluster groups to make sure automatic failover is enabled when cluster mode is enabled |  | [Source](https://github.com/awslabs/cfn-python-lint) | `resources`,`elasticcache` |
+| E3027<a name="E3027"></a> | Validate AWS Event ScheduleExpression format | Validate the formation of the AWS::Event ScheduleExpression |  | [Source](https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html) | `resources`,`events` |
 | E3030<a name="E3030"></a> | Check if properties have a valid value | Check if properties have a valid value in case of an enumator |  | [Source](https://github.com/aws-cloudformation/cfn-python-lint/blob/master/docs/cfn-resource-specification.md#allowedvalue) | `resources`,`property`,`allowed value` |
 | E3031<a name="E3031"></a> | Check if property values adhere to a specific pattern | Check if properties have a valid value in case of a pattern (Regular Expression) |  | [Source](https://github.com/awslabs/cfn-python-lint/blob/master/docs/cfn-resource-specification.md#allowedpattern) | `resources`,`property`,`allowed pattern`,`regex` |
 | E3032<a name="E3032"></a> | Check if a list has between min and max number of values specified | Check lists for the number of items in the list to validate they are between the minimum and maximum |  | [Source](https://github.com/awslabs/cfn-python-lint/blob/master/docs/cfn-resource-specification.md#allowedpattern) | `resources`,`property`,`list`,`size` |

src/cfnlint/rules/resources/events/RuleScheduleExpression.py

@@ -0,0 +1,98 @@
+"""
+  Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+  Permission is hereby granted, free of charge, to any person obtaining a copy of this
+  software and associated documentation files (the "Software"), to deal in the Software
+  without restriction, including without limitation the rights to use, copy, modify,
+  merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so.
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+"""
+from cfnlint import CloudFormationLintRule
+from cfnlint import RuleMatch
+
+
+class RuleScheduleExpression(CloudFormationLintRule):
+    """Validate AWS Events Schedule expression format"""
+    id = 'E3027'
+    shortdesc = 'Validate AWS Event ScheduleExpression format'
+    description = 'Validate the formation of the AWS::Event ScheduleExpression'
+    source_url = 'https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html'
+    tags = ['resources', 'events']
+
+    def initialize(self, cfn):
+        """Initialize the rule"""
+        self.resource_property_types = ['AWS::Events::Rule']
+
+    def check_rate(self, value, path):
+        """Check Rate configuration"""
+        matches = []
+        # Extract the expression from rate(XXX)
+        rate_expression = value[value.find('(')+1:value.find(')')]
+
+        if not rate_expression:
+            matches.append(RuleMatch(path, 'Rate value of ScheduleExpression cannot be empty'))
+        else:
+            # Rate format: rate(Value Unit)
+            items = rate_expression.split(' ')
+
+            if len(items) != 2:
+                message = 'Rate expression must contain 2 elements (Value Unit), rate contains {} elements'
+                matches.append(RuleMatch(path, message.format(len(items))))
+            else:
+                # Check the Value
+                if not items[0].isdigit():
+                    message = 'Rate Value ({}) should be of type Integer.'
+                    matches.append(RuleMatch(path, message.format(items[0])))
+
+        return matches
+
+    def check_cron(self, value, path):
+        """Check Cron configuration"""
+        matches = []
+        # Extract the expression from cron(XXX)
+        cron_expression = value[value.find('(')+1:value.find(')')]
+
+        if not cron_expression:
+            matches.append(RuleMatch(path, 'Cron value of ScheduleExpression cannot be empty'))
+        else:
+            # Rate format: cron(Minutes Hours Day-of-month Month Day-of-week Year)
+            items = cron_expression.split(' ')
+
+            if len(items) != 6:
+                message = 'Cron expression must contain 6 elements (Minutes Hours Day-of-month Month Day-of-week Year), cron contains {} elements'
+                matches.append(RuleMatch(path, message.format(len(items))))
+
+        return matches
+
+    def check_value(self, value, path):
+        """Count ScheduledExpression value"""
+        matches = []
+
+        # Value is either "cron()" or "rate()"
+        if value.startswith('rate(') and value.endswith(')'):
+            matches.extend(self.check_rate(value, path))
+        elif value.startswith('cron(') and value.endswith(')'):
+            matches.extend(self.check_cron(value, path))
+        else:
+            message = 'Invalid ScheduledExpression specified ({}). Value has to be either cron() or rate()'
+            matches.append(RuleMatch(path, message.format(value)))
+
+        return matches
+
+    def match_resource_properties(self, properties, _, path, cfn):
+        """Check CloudFormation Properties"""
+        matches = []
+
+        matches.extend(
+            cfn.check_value(
+                obj=properties, key='ScheduleExpression',
+                path=path[:],
+                check_value=self.check_value
+            ))
+
+        return matches

test/fixtures/templates/bad/resources/events/rule_schedule_expression.yaml

@@ -0,0 +1,31 @@
+---
+AWSTemplateFormatVersion: "2010-09-09"
+Resources:
+  MyScheduledRule1:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "daily" # has to be cron() or rate()
+  MyScheduledRule2:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron()" # Empty cron
+  MyScheduledRule3:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "rate()" # Empty rate
+  MyScheduledRule4:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "rate(5)" # Not enough values
+  MyScheduledRule5:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "rate(5 minutes daily)" # Too many values
+  MyScheduledRule6:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "rate(five minutes)" # Value has to be a digit
+  MyScheduledRule7:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(0 */1 * * WED)" # Not enough values

test/fixtures/templates/good/resources/events/rule_schedule_expression.yaml

@@ -0,0 +1,42 @@
+---
+AWSTemplateFormatVersion: "2010-09-09"
+Description: >
+  Valid scheduled expression accordig to the examples in the documentation
+  (https://docs.aws.amazon.com/lambda/latest/dg/tutorial-scheduled-events-schedule-expressions.html)
+Resources:
+  MyCronRule1:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(15 10 * * ? *)" # 10:15 AM (UTC) every day
+  MyCronRule2:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(0 18 ? * MON-FRI *)" # 6:00 PM Monday through Friday
+  MyCronRule3:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(0 8 1 * ? *)" # 8:00 AM on the first day of the month
+  MyCronRule4:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(0/10 * ? * MON-FRI *)" # Every 10 min on weekdays
+  MyCronRule5:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(0/5 8-17 ? * MON-FRI *)" # Every 5 minutes between 8:00 AM and 5:55 PM weekdays
+  MyCronRule6:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: "cron(0 9 ? * 2#1 *)" # 9:00 AM on the first Monday of each month
+  MyRateRule1:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: rate(5 minutes) # Every 5 minutes
+  MyRateRule2:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: rate(1 hour) # Every hour
+  MyRateRule3:
+    Type: AWS::Events::Rule
+    Properties:
+      ScheduleExpression: rate(7 days) # Every seven days

test/rules/resources/events/test_rule_schedule_expression.py

@@ -0,0 +1,37 @@
+"""
+  Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy of this
+  software and associated documentation files (the "Software"), to deal in the Software
+  without restriction, including without limitation the rights to use, copy, modify,
+  merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+"""
+from cfnlint.rules.resources.events.RuleScheduleExpression import RuleScheduleExpression  # pylint: disable=E0401
+from ... import BaseRuleTestCase
+
+
+class TestRuleScheduleExpression(BaseRuleTestCase):
+    """Test Event Rules ScheduledExpression format"""
+    def setUp(self):
+        """Setup"""
+        super(TestRuleTargetsLimit, self).setUp()
+        self.collection.register(RuleScheduleExpression())
+        self.success_templates = [
+            'test/fixtures/templates/good/resources/events/rule_schedule_expression.yaml'
+        ]
+
+    def test_file_positive(self):
+        """Test Positive"""
+        self.helper_file_positive()
+
+    def test_file_negative_alias(self):
+        """Test failure"""
+        self.helper_file_negative('test/fixtures/templates/bad/resources/events/rule_schedule_expression.yaml', 7)