A VS Code extension that makes writing CloudFormation templates less painful.
The popular YAML extensions don't know anything about CloudFormation — so you get red squiggly lines on !Ref, no autocomplete for resource types, and no help when you forget a required property. This fixes that.
What it does
Autocomplete for resource types
Type AWS:: and get a dropdown of every AWS resource type (2800+). Filter as you type — AWS::Lambda:: shows only Lambda resources.
Property completions
Inside a Properties block, it suggests the valid properties for that resource type. Required properties are marked so you know what you can't skip.
!Ref completions and validation
Type !Ref and see every resource and parameter defined in the current template. If a !Ref points to something that doesn't exist, you get a warning.
!GetAtt completions and validation
Type !GetAtt to pick a resource, then automatically see the valid attributes for that resource type. Warns if the resource doesn't exist or the attribute isn't valid.
!Sub variable completions and validation
Inside a !Sub string, type ${ and see resources, parameters, and pseudo-parameters. Warns if a variable doesn't resolve to anything in the template.
!ImportValue completions
Type !ImportValue and see the outputs defined in the current template.
Required property warnings
If you're missing a required property on a resource, the logical ID gets a yellow underline telling you exactly what's missing.
Hover documentation
Hover over a resource type, property name, or logical ID to see the AWS description, type info, and available !GetAtt attributes.
Go-to-definition
Cmd+click (or Ctrl+click) on a !Ref, !GetAtt, or ${...} target to jump to where that resource or parameter is defined.
No false positives
!Ref, !Sub, !GetAtt, !ImportValue, !If, !Join and all other CloudFormation intrinsic functions are treated as valid. No more red squiggly lines on correct templates.
Getting started
Install the extension, open any CloudFormation YAML template, and it works automatically. It detects CloudFormation templates by looking for a Resources: block and switches into CloudFormation mode.
It only activates on CloudFormation templates — regular YAML files are left alone.
Supported intrinsic functions
All standard CloudFormation intrinsic functions are recognized:
!Ref !Sub !GetAtt !ImportValue !If !Join !Select !Split !FindInMap !Base64 !Cidr !And !Or !Not !Equals !Transform
Resource data
The extension uses the official AWS CloudFormation resource provider schemas from us-east-1, pulled directly from AWS. This covers 2800+ resource types with accurate property definitions, required/optional indicators, descriptions, and return attributes.
To regenerate the schema data (e.g. after AWS adds new services):
npm run fetch-schema
Contributing
Issues and PRs are welcome at github.com/Robert076/cloudformation-lens.
If something doesn't work the way you'd expect, open an issue with your template snippet and what you expected to happen.
License
MIT
