Overview
Language support for AWS CloudFormation templates in JSON and YAML, powered by the
AWS CloudFormation Language Server.
The extension is a standalone client for the language server: it installs and updates the server, keeps it running,
and adds an AWS region selector to the status bar.
Features
Editing
- Completion: resource types, properties, intrinsic functions, template sections, and references to parameters,
conditions, and mappings, including inline completions while you type
- Hover documentation: contextual help for resources, properties, and functions
- Go to definition: navigate to the definition of a referenced parameter, resource, condition, or mapping
- Document symbols: template structure in the Outline view and breadcrumbs
- Code actions: quick fixes for diagnostics, extracting hardcoded values to parameters, and inserting related
resources
Validation
- Syntax: immediate feedback on JSON and YAML errors
- Schema: resource schema validation using the schemas of the selected AWS region
- cfn-lint: linting with the bundled cfn-lint (no local Python installation required) or a local
cfn-lint
executable of your choice, with configurable delay and rule customization
- CloudFormation Guard: policy-as-code validation against managed rule packs (default:
cis-aws-benchmark-level-1) or a custom rules file
File support
- A
CloudFormation language mode with syntax highlighting for .template and .cfn files
- CloudFormation templates in
.json, .yaml, .yml, and .txt files
Getting started
- Install the extension (see Installation).
- Open a CloudFormation template. The language server starts automatically and diagnostics appear in the editor and
the Problems view.
- Pick the AWS region whose resource schemas you want to validate against: click the
AWS Region item in the status
bar or run AWS CloudFormation: Update Region. The default is us-east-1, and the choice is remembered across
sessions.
Requirements
- Visual Studio Code 1.91 or later
- Internet access on first activation: the extension downloads a verified release of the language server into the
user cache directory (
~/Library/Caches/aws/language-servers on macOS, %LOCALAPPDATA%\aws\language-servers on
Windows, ~/.cache/aws/language-servers on Linux). Later activations reuse the cached install and fall back to it
when a newer release cannot be downloaded. Regional resource schemas are downloaded on demand from the public
CloudFormation schema endpoint of the selected region.
AWS account access
The extension does not currently pass AWS credentials to the language server. Everything above works without an AWS
account. Server features that call AWS APIs on your behalf, such as deploying a template, listing stacks, server-side
template validation, and importing resource state, are not available in this extension.
Commands
| Command |
Description |
AWS CloudFormation: Update Region |
Select the AWS region whose resource schemas are used |
AWS CloudFormation: Restart LSP |
Restart the language server |
Settings
| Setting |
Default |
Description |
aws.cloudformation.hover.enabled |
true |
Enable hover documentation |
aws.cloudformation.completion.enabled |
true |
Enable completion |
aws.cloudformation.diagnostics.cfnLint.enabled |
true |
Enable cfn-lint diagnostics |
aws.cloudformation.diagnostics.cfnLint.lintOnChange |
true |
Run cfn-lint when the document changes |
aws.cloudformation.diagnostics.cfnLint.delayMs |
3000 |
Delay before running cfn-lint after a change |
aws.cloudformation.diagnostics.cfnLint.path |
"" |
Path to a local cfn-lint executable; empty uses the bundled version |
aws.cloudformation.diagnostics.cfnLint.customization |
{ "includeChecks": ["I"] } |
cfn-lint rule customization (ignore, include, mandatory, regions, ...) |
aws.cloudformation.diagnostics.cfnGuard.enabled |
true |
Enable CloudFormation Guard diagnostics |
aws.cloudformation.diagnostics.cfnGuard.validateOnChange |
true |
Run cfn-guard when the document changes |
aws.cloudformation.diagnostics.cfnGuard.delayMs |
1000 |
Delay before running cfn-guard after a change |
aws.cloudformation.diagnostics.cfnGuard.enabledRulePacks |
["cis-aws-benchmark-level-1"] |
Managed rule packs to validate against |
aws.cloudformation.diagnostics.cfnGuard.rulesFile |
"" |
Path to a custom cfn-guard rules file; empty uses the enabled rule packs |
aws.cloudformation.trace.server |
"off" |
Trace communication with the language server (messages, verbose) |
aws.iac.telemetry.enabled |
false |
Share anonymous usage telemetry with AWS |
aws.cloudformation.telemetry.logLevel |
"info" |
Log level of the extension output channel; applies after a window reload |
Telemetry
Telemetry is off by default. On first activation the extension asks whether to share anonymous usage data with AWS;
you can change the choice at any time with aws.iac.telemetry.enabled. The setting is specific to this extension;
it does not read or change the telemetry preference of any other extension. See the language server's
telemetry documentation
for what is collected.
Troubleshooting
- The extension and the language server log to the AWS CloudFormation channel in the Output view. Set
aws.cloudformation.telemetry.logLevel to debug for more detail, and aws.cloudformation.trace.server to
messages or verbose to see the protocol traffic.
- If the server stops responding, run
AWS CloudFormation: Restart LSP. A restart re-resolves the server install and
repairs an incomplete one.
- To force a fresh download, delete the
language-servers/cloudformation-languageserver folder under the cache
directory listed in Requirements and restart the server.
- Bugs and feature requests: GitHub issues.
Installation
Install AWS CloudFormation from the Visual Studio Code Marketplace or Open VSX, or download the .vsix package
from the releases page and install it with
code --install-extension aws-iac-vscode.vsix or Extensions: Install from VSIX... in VS Code.
Contributing
See CONTRIBUTING.md for how to report issues and submit pull requests, including how to report
security issues. This project follows the Code of Conduct.
License
Licensed under the Apache License 2.0. Third-party licenses are listed in
THIRD-PARTY-LICENSES.txt.
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