AWS SAM transform

The AWS Serverless Application Model (AWS SAM) transform is a AWS CloudFormation macro that transforms SAM templates into CloudFormation templates.

To use the SAM transform, add AWS::Serverless-2016-10-31 to the Transform section of your CloudFormation template.

Benefits of using the SAM transform include:

Built-in best practices and sane defaults.
Local testing and debugging with the AWS SAM CLI.
Extension of the CloudFormation template syntax.

Getting started

Save the following as template.yaml:

Transform: AWS::Serverless-2016-10-31
Resources:
  MyFunction:
    Type: AWS::Serverless::Function
    Properties:
      Runtime: nodejs24.x
      Handler: index.handler
      InlineCode: |
        exports.handler = async (event) => {
          console.log(event);
        }

And deploy it with the SAM CLI:

sam sync --stack-name sam-app

The AWS::Serverless::Function resource will create a AWS Lambda function that logs events it receives.

Under the hood, the template is transformed into the JSON equivalent of the following CloudFormation template:

Resources:
  MyFunction:
    Type: AWS::Lambda::Function
    Properties:
      Code:
        ZipFile: |
          exports.handler = async (event) => {
            console.log(event);
          }
      Handler: index.handler
      Role: !GetAtt MyFunctionRole.Arn
      Runtime: nodejs24.x
      Tags:
        - Key: lambda:createdBy
          Value: SAM
  MyFunctionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Action:
              - sts:AssumeRole
            Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
      Tags:
        - Key: lambda:createdBy
          Value: SAM

For a more thorough introduction, see the this tutorial in the Developer Guide.

Contributing

Setting up development environment

You'll need to have Python 3.8+ installed.

Create a virtual environment:

python3 -m venv .venv
source .venv/bin/activate

Set up dependencies:

make init

Run tests:

make pr

See DEVELOPMENT_GUIDE.md for further development instructions, and CONTRIBUTING.md for the contributing guidelines.

Getting help

The best way to interact with the team is through GitHub. You can either create an issue or start a discussion.

You can also join the #samdev channel on Slack.

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