[0xTaoZ]

What

Fixes #4714.

This updates SAM implicit-resource handling so AWS::Serverless::StateMachine Api events create the same synthetic implicit ServerlessRestApi/stage context as function Api events. It also teaches Fn::Sub validation that SAM ${Api.Stage} references are generated stage-resource references, not CloudFormation Fn::GetAtt attributes on the API resource.

Why

SAM rewrites ${ServerlessRestApi.Stage} to the generated stage logical id during transform. cfn-lint was treating it as a GetAtt against AWS::Serverless::Api/AWS::ApiGateway::RestApi, causing false positives after the schema-based SAM validation changes.

Tests

• .venv/bin/python -m pytest test/unit/module/context/test_inject_sam_implicit.py test/unit/rules/functions/test_sub.py -q
• .venv/bin/python -m pytest test/unit/rules/functions/test_sub.py test/unit/rules/functions/test_getatt.py test/unit/module/context/test_inject_sam_implicit.py -q
• .venv/bin/ruff check src/cfnlint/context/context.py src/cfnlint/rules/functions/Sub.py test/unit/module/context/test_inject_sam_implicit.py test/unit/rules/functions/test_sub.py
• .venv/bin/ruff format --check src/cfnlint/context/context.py src/cfnlint/rules/functions/Sub.py test/unit/module/context/test_inject_sam_implicit.py test/unit/rules/functions/test_sub.py
• git diff --check

Note: I also tried a CLI smoke with the issue-shaped SAM templates, but this local environment could not download enhanced schemas due to CERTIFICATE_VERIFY_FAILED, so the focused unit tests are the reliable validation here.

Supersedes #4719. The commit and scope are unchanged.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.72%. Comparing base (be66fb3) to head (6e9f4c3).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/cfnlint/rules/functions/Sub.py	83.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4730      +/-   ##
==========================================
- Coverage   94.72%   94.72%   -0.01%     
==========================================
  Files         439      439              
  Lines       15840    15858      +18     
  Branches     3060     3067       +7     
==========================================
+ Hits        15005    15021      +16     
- Misses        456      457       +1     
- Partials      379      380       +1     

Flag	Coverage Δ
unittests	94.72% <88.88%> (-0.01%)	⬇️

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