E1010 false positive: GetAtt <app>.Outputs.* on AWS::Serverless::Application rejected since 1.54.0 (only StackId allowed)

[jpinsolle-bc]

CloudFormation Lint Version

1.55.1

What operating system are you using?

macOS 26.6, Ubuntu

Describe the bug

#Problem
!GetAtt <SomeApplication>.Outputs.<OutputName> on an AWS::Serverless::Application resource is reported as invalid:

E1010 'Outputs.TopicName' is not one of ['StackId'] in ['us-east-1']
template.yaml:12:7

This is the documented way to consume a nested application's outputs, and it works at deploy time: SAM transforms AWS::Serverless::Application into AWS::CloudFormation::Stack, whose outputs are reachable via Outputs.<name>.

Bisection points at the removal of the SAM translator in #4491:

version	result
1.53.3	clean
1.54.0	E1010
1.55.1	E1010

Root cause, as far as I can tell: GetAtts.__init__ in cfnlint/schema/_getatts.py grants the Outputs\..* wildcard to exactly two type names — AWS::CloudFormation::Stack and AWS::ServiceCatalog::CloudFormationProvisionedProduct:

if schema.type_name == "AWS::CloudFormation::Stack":
    self._attrs["Outputs\\..*"] = "/properties/CfnLintStringType"
    return

if schema.type_name == "AWS::ServiceCatalog::CloudFormationProvisionedProduct":
    ...

Before #4491 the translator rewrote the resource to AWS::CloudFormation::Stack, so the first branch applied. Now the resource keeps its SAM type, and the SAM schema for it declares a single GetAtt-able attribute:

typeName: AWS::Serverless::Application
readOnlyProperties: ['/properties/StackId']

so _attrs ends up as ['StackId'] and any Outputs.* lookup fails.

Expected behavior

No E1010.
Outputs.<anything> should be accepted on AWS::Serverless::Application, as it is on AWS::CloudFormation::Stack.

Reproduction template

AWSTemplateFormatVersion: "2010-09-09"
Transform: "AWS::Serverless-2016-10-31"
Resources:
  ChildApplication:
    Type: AWS::Serverless::Application
    Properties:
      Location: ./child.yaml

  TopicPolicy:
    Type: AWS::SNS::TopicPolicy
    Properties:
      Topics:
        - !GetAtt ChildApplication.Outputs.TopicArn
      PolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: Allow
            Principal:
              Service: events.amazonaws.com
            Action: "sns:Publish"
            Resource: "*"

child.yaml — declares the output referenced above:

AWSTemplateFormatVersion: "2010-09-09"
Resources:
  Topic:
    Type: AWS::SNS::Topic
Outputs:
  TopicArn:
    Value: !Ref Topic