chore(lambda): handle Runtime.ALL correctly in LayerVersion compatibleRuntimes

[pahud]

Issue # (if applicable)

Closes #35348.

Reason for this change

Runtime.ALL contains 43+ runtime entries (including deprecated ones), but AWS Lambda limits compatibleRuntimes to maximum 15 entries and only accepts currently supported runtimes. When users specify compatibleRuntimes: Runtime.ALL for Lambda layers, deployment fails with CloudFormation validation errors:

• "Member must have length less than or equal to 15"
• "Member must satisfy enum value set" for supported runtimes only

This breaks existing user code that relies on the documented Runtime.ALL constant for Lambda layers.

Description of changes

Modified the LayerVersion constructor to detect when compatibleRuntimes is set to Runtime.ALL and treat it as undefined, allowing AWS to use its default "all supported runtimes" behavior:

• Added conditional logic in CfnLayerVersion resource creation to check for Runtime.ALL via reference equality
• When Runtime.ALL is detected, compatibleRuntimes is set to undefined in the CloudFormation template
• When undefined, AWS Lambda defaults to supporting all currently supported runtimes (the intended behavior)
• All other behavior remains unchanged - specific runtime arrays and undefined work as before
• Updated documentation to clarify that Runtime.ALL is equivalent to undefined

Technical Implementation:

compatibleRuntimes: (props.compatibleRuntimes === Runtime.ALL)
  ? undefined
  : props.compatibleRuntimes?.map(r => r.name),

Describe any new or updated permissions being added

N/A - No IAM permissions or resource access changes.

Description of how you validated changes

• Unit tests: Added comprehensive test cases using test.each to verify that both Runtime.ALL and undefined result in omitting CompatibleRuntimes from the CloudFormation template. This eliminates code duplication and follows Jest best practices. All existing layer tests continue to pass (7/7).
• Integration tests: No additional integration tests required as this change leverages existing AWS Lambda service behavior when CompatibleRuntimes is omitted from the CloudFormation template. The AWS service automatically applies compatibility with all currently supported runtimes, which is the intended behavior for Runtime.ALL.

Test Coverage:

• ✅ Runtime.ALL produces undefined in CloudFormation template
• ✅ undefined compatibleRuntimes produces undefined in CloudFormation template
• ✅ Specific runtime arrays work unchanged
• ✅ Empty runtime array validation still throws error
• ✅ All existing layer functionality preserved
• ✅ Refactored tests using test.each to eliminate duplication

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[alvazjor]

@pahud
The description of the PR mentions integ test being ready, but I am not understanding if they are already in place, or if you planned to add some additional.

[alvazjor]

The 2 tests that we are adding are a duplication of code, since they are identical but with just changing the compatibleRuntimes value. I'd suggest we better do something like this to avoid the duplication of code:

test.each([
  ['Runtime.ALL is handled correctly', { compatibleRuntimes: lambda.Runtime.ALL }],
  ['undefined compatibleRuntimes is handled correctly', {}]
])('%s by omitting compatibleRuntimes', (_, props) => {
  // GIVEN
  const stack = new cdk.Stack();
  const bucket = new s3.Bucket(stack, 'Bucket');
  const code = new lambda.S3Code(bucket, 'ObjectKey');

  // WHEN
  new lambda.LayerVersion(stack, 'LayerVersion', {
    code,
    ...props
  });

// the remaining stays the same

[pahud]

All addressed. Thank you

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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