AWS::LanguageExtensions transform - AWS CloudFormation
UsageSupport for additional functionsConsiderationsExamplesRelated resources

This is the new AWS CloudFormation Template Reference Guide. Please update your bookmarks and links. For help getting started with CloudFormation, see the AWS CloudFormation User Guide.

AWS::LanguageExtensions transform

This topic describes how to use the AWS::LanguageExtensions transform to enable additional functions and capabilities that are not available by default.

The AWS::LanguageExtensions is a CloudFormation macro that, when referenced in your stack template, updates any intrinsic function defined by the transform to its resolved value within the template when you create or update a stack using a change set.

By including this transform in your CloudFormation template, you can access additional features, such as Fn::ForEach, which allows for more advanced operations like iteration. You can also use intrinsic functions in places where they're typically not allowed, such as in Ref and Fn::GetAtt functions.

Usage

To use the AWS::LanguageExtensions transform, you must declare it at the top level of your CloudFormation template. You can't use AWS::LanguageExtensions as a transform embedded in any other template section.

The declaration must use the literal string AWS::LanguageExtensions as its value. You can't use a parameter or function to specify a transform value.

Syntax

To declare this transform in your CloudFormation template, use the following syntax:

JSON

{
  "Transform":"AWS::LanguageExtensions",
  "Resources":{
    ...
  }
}

YAML

Transform: AWS::LanguageExtensions
Resources:
  ...

The AWS::LanguageExtensions transform is a standalone declaration with no additional parameters.

Support for additional functions

The AWS::LanguageExtensions transform supports the following additional functions:

Considerations

When using the AWS::LanguageExtensions transform, keep the following considerations in mind:

  • When you update a stack that uses the AWS::LanguageExtensions transform, we recommend that you don't use the Use existing template option in the CloudFormation console, or the equivalent command line option --use-previous-template. The AWS::LanguageExtensions transform resolves parameters to literal values during processing. When you use --use-previous-template, CloudFormation uses this processed template with the old literal values, preventing new parameter values and Systems Manager parameter updates from being applied. Instead, provide the original template to ensure parameters are re-resolved with current values.

  • Short-form YAML syntax isn't supported within a template for intrinsic functions that are only available in the AWS::LanguageExtensions transform. Use explicit references to these functions. For example, use Fn::Length instead of !Length.

  • The AWS SAM CLI currently doesn't support the Fn::ForEach intrinsic function of the AWS::LanguageExtensions transform.

  • If you're using multiple transforms, use a list format. If you're using custom macros, place AWS-provided transforms after your custom macros. If you're using both the AWS::LanguageExtensions and AWS::Serverless transforms, the AWS::LanguageExtensions transform must come before the AWS::Serverless transform in the list.

  • Functions and attributes provided by the AWS::LanguageExtensions transform are only supported in the Resources, Conditions, and Outputs sections of your template.

Examples

The following examples show how to use the AWS::LanguageExtensions transform to use the Fn::Length intrinsic function, defined by the transform.

JSON

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Parameters": {
        "QueueList": {
            "Type": "CommaDelimitedList"
        },
        "QueueNameParam": {
            "Description": "Name for your SQS queue",
            "Type": "String"
        }
    },
    "Resources": {
        "Queue": {
            "Type": "AWS::SQS::Queue",
            "Properties": {
                "QueueName": {
                    "Ref": "QueueNameParam"
                },
                "DelaySeconds": {
                    "Fn::Length": {
                        "Ref": "QueueList"
                    }
                }
            }
        }
    }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Parameters:
  QueueList:
    Type: CommaDelimitedList
  QueueNameParam:
    Description: Name for your SQS queue
    Type: String
Resources:
  Queue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: !Ref QueueNameParam
      DelaySeconds:
        'Fn::Length': !Ref QueueList

For more examples, see the following topics.

For general information about using macros, see Perform custom processing on CloudFormation templates with template macros in the AWS CloudFormation User Guide.