AWS CloudFormation Guard - VS Code Extension

Language support for AWS CloudFormation Guard DSL, providing syntax highlighting, IntelliSense, diagnostics, and formatting capabilities.

Note: This extension was built using AI agent to demonstrate rapid VS Code extension development with the Language Server Protocol.

Features

✅ Syntax Highlighting

Keywords: rule, let, when, some, this, or, not
Operators: ==, !=, >, <, >=, <=, IN, exists, empty, type checks
16 built-in functions with proper highlighting
Variables (%variable_name)
Comments (#)
Custom error messages (<< >>)

✅ IntelliSense & Code Completion

Keyword completion
Function completion with snippets
Operator suggestions
Variable references

✅ Diagnostics

Syntax error detection
Undefined variable warnings
Real-time validation

✅ Hover Information

Function signatures and descriptions
Keyword explanations
Operator documentation

✅ Code Formatting

Auto-indentation
Consistent spacing
Brace alignment

Installation

From VSIX

Download the .vsix file from releases
Open VS Code
Go to Extensions view
Click ... → "Install from VSIX"
Select the downloaded file

From Source

cd vscode-extension
npm install
npm run compile

Then press F5 to launch the Extension Development Host.

Usage

Create a .guard file
Start writing Guard rules - IntelliSense will activate automatically
Use Ctrl+Space for completion suggestions
Hover over keywords/functions for documentation

Example Guard Rule

let s3_buckets = Resources.*[ Type == 'AWS::S3::Bucket' ]

rule s3_bucket_encrypted when %s3_buckets !empty {
    %s3_buckets.Properties.BucketEncryption exists
    %s3_buckets.Properties.BucketEncryption.ServerSideEncryptionConfiguration[*] {
        ServerSideEncryptionByDefault.SSEAlgorithm IN ["aws:kms", "AES256"]
    }
    <<
        Violation: S3 buckets must have encryption enabled
        Fix: Enable server-side encryption on the bucket
    >>
}

Guard DSL Reference

Keywords

rule - Define a named rule
let - Variable assignment
when - Conditional execution
some - At-least-one quantifier
this - Current context reference
or - Disjunction operator
not - Negation

Operators

Binary: ==, !=, >, <, >=, <=, IN
Unary: exists, empty, is_string, is_list, is_struct, is_bool, is_int, is_float, is_null

Built-in Functions (16 total)

String: json_parse, regex_replace, join, to_lower, to_upper, substring, url_decode
Collection: count, keys
Converters: parse_int, parse_float, parse_string, parse_boolean, parse_char
Date/Time: parse_epoch, now

Note: Functions must be used with variable assignment: let result = count(Resources.*)

Development

Build

npm run compile

Watch Mode

npm run watch

Debug

Open the extension folder in VS Code
Press F5 to launch Extension Development Host
Open a .guard file to test

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Guard

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