Add Spec file and test for properties Allowed Values

[fatbasstard]

Issue #50

Introduce new rule E3030 to check allowed values as mentioned in the documentation. Properties sometimes have a list of "allowed values" (e.g. https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-vpc.html#cfn-aws-ec2-vpc-instancetenancy).

These values are not in the Spec files, and probably will never be. This PR will add a new Additional Spec file (AllowedValues.json) which contains these allowed values in the same format as the Spec files itself, and the other Additional Spec files. In this way all Allowed Values are maintained in a single place which makes more transparent, easier to maintain and remove this logic from current (existing) rules.

This is a first version (MVP) that introduces the new Rule and the definition file. The definition file contains a first set of known allowed values. Also "moved" some of the existing rule logic already (including altering/moving the test logic).

It's an MVP rule at the moment that is open for extension/improvement when required. By adding it already we can move move allowed values in the future from rules and more values can be added to the definition.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[kddejong]

I love these types of rules as it allows for making new checks a lot easier.

We should remove rule E2531 as well as that should be covered by this.

[kddejong]

I would use the cfn.check_value function to check the value against the supported lists.
With this version Runtime: !If [myCondition, nodejs4.3, nodejs4.4] will not show a failure.

[fatbasstard]

Funny detail BTW. This example breaks the existing Runtime check (E2531 ):

E0002 Unknown exception while processing rule E2531: sequence item 5: expected str instance, int found
test/fixtures/templates/bad/properties_allowedvalues.yaml:1:

[kddejong]

Yea that is covered by pull request #457

[kddejong]

Since you are using match instead of the resource and property match functions this isn't providing a failure.

myBucketGood:
    Type: AWS::S3::Bucket
    Properties:
      VersioningConfiguration:
        Status: Bad

As an example.
https://github.com/awslabs/cfn-python-lint/pull/234/files#diff-dd307d557b713eb258c15a2607351227R203

[cmmeyer]

So looking at this and #234 I wonder if we need two separate files? Seems like the only difference is one is for string values and the other is for resource values, unless I missed something?

Would it make sense to consolidate to a single extended spec file, or even patch the existing specs to include value?

[fatbasstard]

Replaced by a new PR that uses the new Spec Patch mechanism