fix: parse nested yaml GetAtt refs correctly

[edwardfoyle]

Description of changes

Per the CFN spec: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-getatt.html, the logic for reading YAML templates had a bug where

!GetAtt myResource.output.propName

would be translated into

{
  "Fn::GetAtt": ["myResource", "output", "propName"]
}

instead of

{
  "Fn::GetAtt": ["myResource", "output.propName"]
}

Issue #, if available

Description of how you validated changes

Unit tested

Checklist

• PR description included
• yarn test passes
• Tests are changed or added

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

[cjihrig]

If there is no . in the string, this will generate the wrong output. I'm not sure if it actually matters though since the GetAtt won't work properly.

[edwardfoyle]

yeah I don't think we need to cover that case here as it's already invalid

[codecov-commenter]

Codecov Report

Merging #7220 (ff514ac) into master (ec1613e) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #7220      +/-   ##
==========================================
- Coverage   52.28%   52.27%   -0.02%     
==========================================
  Files         491      491              
  Lines       25242    25248       +6     
  Branches     4952     4952              
==========================================
  Hits        13199    13199              
- Misses      11091    11097       +6     
  Partials      952      952              

Impacted Files	Coverage Δ
packages/amplify-cli-core/src/cfnUtilities.ts	20.00% <0.00%> (-2.45%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ec1613e...ff514ac. Read the comment docs.

[siegerts]

👋 Hi, this issue was referenced in the v4.50.2 release!

Check out the release notes here https://github.com/aws-amplify/amplify-cli/releases/tag/v4.50.2.