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CFn: handle invalid GetAtt validation#13241

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simonrw merged 2 commits intomainfrom
cfn/fix-getatt-invalid-structure
Oct 8, 2025
Merged

CFn: handle invalid GetAtt validation#13241
simonrw merged 2 commits intomainfrom
cfn/fix-getatt-invalid-structure

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@simonrw simonrw commented Oct 8, 2025

Motivation

While triaging CFn issues we found a couple of errors that were

  File ""/opt/code/localstack/.venv/lib/python3.13/site-packages/localstack/services/cloudformation/engine/v2/change_set_model_preproc.py"", line 563, in _resolve_attribute
    attribute_name = arguments_list[1]
                     ~~~~~~~~~~~~~~^^^
localstack.aws.api.core.CommonServiceException: exception while calling cloudformation.UpdateStack: list index out of range

This is due to an invalid usage of the Fn::GetAtt intrinsic which expects two arguments, the logical resource id and the attribute to fetch. On AWS this raises a validation error during create change set.

Changes

Add two tests covering this situation

@simonrw simonrw added semver: patch Non-breaking changes which can be included in patch releases aws:cloudformation:v2 Issues related to the V2 CloudFormation engine docs: skip Pull request does not require documentation changes notes: skip Pull request does not have to be mentioned in the release notes labels Oct 8, 2025
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Test Results - Preflight, Unit

22 298 tests  ±0   20 555 ✅ ±0   15m 59s ⏱️ +18s
     1 suites ±0    1 743 💤 ±0 
     1 files   ±0        0 ❌ ±0 

Results for commit a31ed23. ± Comparison against base commit 9af2464.

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Test Results (amd64) - Acceptance

7 tests  ±0   5 ✅ ±0   3m 22s ⏱️ +3s
1 suites ±0   2 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit a31ed23. ± Comparison against base commit 9af2464.

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Test Results - Alternative Providers

582 tests   330 ✅  25m 52s ⏱️
  1 suites  252 💤
  1 files      0 ❌

Results for commit a31ed23.

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Test Results (amd64) - Integration, Bootstrap

    5 files      5 suites   2h 40m 1s ⏱️
5 183 tests 4 686 ✅ 497 💤 0 ❌
5 189 runs  4 686 ✅ 503 💤 0 ❌

Results for commit a31ed23.

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LocalStack Community integration with Pro

    2 files  ±0      2 suites  ±0   2h 2m 12s ⏱️ + 3m 54s
4 809 tests +2  4 472 ✅ +2  337 💤 ±0  0 ❌ ±0 
4 811 runs  +2  4 472 ✅ +2  339 💤 ±0  0 ❌ ±0 

Results for commit a31ed23. ± Comparison against base commit 9af2464.

@simonrw simonrw marked this pull request as ready for review October 8, 2025 15:47
pinzon
pinzon approved these changes Oct 8, 2025
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👍 Nice

@simonrw simonrw merged commit c9f9602 into main Oct 8, 2025
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@simonrw simonrw deleted the cfn/fix-getatt-invalid-structure branch October 8, 2025 17:48
baermat pushed a commit that referenced this pull request Oct 13, 2025
@simonrw @baermat
CFn: handle invalid GetAtt validation (#13241)
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@pinzon pinzon pinzon approved these changes

@dominikschubert dominikschubert Awaiting requested review from dominikschubert dominikschubert is a code owner

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