Support template transforms other than SAM

[filipe-amberflo-io]

Is this feature request related to a new rule or cfn-lint capabilities?

No response

Describe the feature you'd like to request

The Serverless Application Model (SAM) is supported by the linter. The template is transformed using AWS SAM before the linter processes the template.

Basically, the above, but for custom transforms.

Describe the solution you'd like

The linting rules should (optionally?) be applied after all transforms, not before.

Additional context

We use a CF macro to set "default values" for properties of the resources in the template (+40 templates)

For instance, default environment variables for lambdas; default network configuration for ECS services, etc...

Today the linter started failing due to NetworkMode not being set in an ECS task definition. If I set it, then the linter fails because NetworkConfuration is required for the given NetworkMode in the related ECS service.

• These values are precisely the ones the macro sets defaults for!

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this feature request

Would this feature include a breaking change?

• ⚠️ This feature might incur a breaking change