Using a linter for best practices on templates

Let’s describe a linter again. A linter is a tool that is used for static source code analysis to flag obvious programming errors and bugs, as well as stylistic and non-idiomatic issues. A linter generally operates on a set of predefined rules and style guides. CloudFormation has two linters available: cfn-lint, a previous generation yet still maintained linter, written in Python, and cloudformation-guard, a policy-based linter written in Rust. In this section, we will take a look at both and find out which one serves the best for our use cases.

Evaluating templates with cfn-lint

cfn-lint is a command-line tool that inspects your template and compares the declared resources against a wide range of written rules.

Unlike the template validator, cfn-lint can detect tricky issues such as missing resource properties or arguments in an intrinsic function.

CloudFormation’s linter is an external tool that can be installed...