CloudFormation validation
Accepted cfn-lint work on intrinsic functions, SAM outputs, lifecycle policies and schema-aware validation.
Eight merged pull requests in cfn-lint as of 3 October 2026.
From a single fix to a technical area
The original entry on this site highlighted an Elasticsearch enum patch. The more useful current story is a sequence of accepted contributions around CloudFormation validation.
The contribution record links every merged PR in the site’s dated snapshot. Closed proposals are not counted as accepted work.
A representative case: lifecycle policies
A bare Fn::Select used as the entire CreationPolicy or UpdatePolicy passed linting, but CloudFormation rejected it unless the language-extension transform resolved it first.
PR #4704 validates those attributes at the owning layer. It preserves global Fn::Select behavior and continues routing ordinary policy objects and Fn::If through the existing validators.
The fix includes policy regression cases and checks around intrinsic-function behavior. It was merged in September 2026.
Other accepted work
- SAM application GetAtt outputs
- Negative Fn::Select indexes
- FindInMap DefaultValue without a transform
- Single-property schema maxProperties warnings
What I learned
A validator is not just a list of rules. It is a composition of transforms, schema context and intrinsic-function resolution. A symptom can appear in one rule while the correct fix belongs in another layer.
Scope of the claim
I contribute focused fixes and regression tests. I do not maintain cfn-lint or imply ownership of the project. A PR under review is a proposal until the upstream maintainers accept it.