Cfn-python-lint: Need to validate that resource type is a string

[miparnisari]

cfn-lint version: (cfn-lint --version) 0.30.1

Description of issue.

[PatMyron]

https://github.com/aws-cloudformation/cfn-python-lint/blob/b788cc9bd3d49ed20d5f2e58602755a0ef37f52c/src/cfnlint/rules/resources/ServerlessTransform.py#L36

https://github.com/aws-cloudformation/cfn-python-lint/blob/2d7ed333e5514896c07a6514eb8a84907b536f29/src/cfnlint/rules/resources/Configuration.py#L63

https://github.com/aws-cloudformation/cfn-python-lint/blob/2d7ed333e5514896c07a6514eb8a84907b536f29/src/cfnlint/rules/resources/Configuration.py#L96

startswith getting called indirectly in E1010

---

bit of an odd use case I'd rather not explicitly check in every rule though, maybe there's somewhere earlier like rules/__init__.py this could be caught?

[miparnisari]

The code lines you pointed out are all using either cfn.template.get('Resources', {}).items() or cfn.get_resources().items(). If we can change all instances of the former to the latter, maybe we can make a change within cfn.get_resources():

results = {}
for k, v in resources.items():
    if isinstance(v, dict):
        existing_resource_type = v.get('Type', None)
        if not isinstance(existing_resource_type, six.string_types):
            raise ValueError("A resource type has to be a string")
        if (existing_resource_type in resource_type) or (not resource_type and existing_resource_type is not None):
            results[k] = v

return results

[kddejong]

@miparnisari I completely agree catching it in get_resources(). I tried to make the functions like cfn.get_resources() return resources only if they are valid. No value in returning something if the Type is a number or not even specified. It should be a safe way to get back "valid" resources that any rule or even other core functionality can use.