Error handle invalid YAML with LoadMode.DBT_MANIFEST and RenderConfig.selector

[YourRoyalLinus]

Description

Ensure that DAG parsing only fails for DAGs that are attempting to render using a misconfigured yaml selector.

This was done by collecting any errors during yaml selector parsing and raising an exception when the selector is accessed rather than when the issue is encountered.

The exception to this is for invalid yaml structures. In those cases, we can't be certain whether we have a valid selector name or definition. When the graph attempts to grab the parsed selector, it would always get a selector not found exception, hiding the error messages related to the invalid structure.

As a result, if there is an invalid yaml structure, all DAGs using LoadMode.DBT_MANIFEST and RenderConfig.selector will fail during dag parse. As long as a user never directly modifies the manifest.json, this should not occur.

When doing local QA, I created separate example DAGs, however keeping them did not seem valuable as the unit tests cover the expected behavior.

Follow up from #2257

Related Issue(s)

closes #2312

Breaking Change?

N/A

Checklist

• I have made corresponding changes to the documentation (if required)
• I have added tests that prove my fix is effective or that my feature works

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[Copilot]

Pull request overview

This PR improves error handling for YAML selector parsing by deferring most parsing errors until selector access rather than failing immediately at parse time. This ensures that DAG parsing only fails for DAGs actually using a misconfigured selector, while still failing immediately for structural YAML errors that prevent proper selector identification.

Changes:

• Modified selector parsing to collect errors during parse and raise them on selector access via get_parsed()
• Updated all parsing methods to return error lists alongside parsed results
• Added comprehensive test coverage for multiple error scenarios including nested errors and complex selector definitions

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
cosmos/dbt/selector.py	Refactored all parsing methods to return tuples including error lists; modified get_parsed() to raise errors when accessing selectors with parsing issues
tests/dbt/test_selector.py	Added extensive tests for multi-error scenarios and updated existing tests to call get_parsed() instead of expecting errors from parse()
tests/dbt/test_graph.py	Updated selector cache hash value to reflect implementation changes
docs/configuration/selecting-excluding.rst	Added documentation explaining the two categories of errors (structural vs definition) and when each is raised

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[YourRoyalLinus]

I also noticed a bug that prevents the cache from invalidating when a DAG initially swaps LoadModes from DBT_LS to `DBT_MANIFEST or vice versa. The fix is extremely small (8 simple loc + 2 new unit tests).

Would you prefer a separate issue and PR for tracking or is there a threshold that's small enough to lump those changes into this PR? My preference is to separate them, for many reasons, but I don't want to pile on new issues and PRs unnecessarily.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.93%. Comparing base (b48b9f5) to head (9f41ab1).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2316      +/-   ##
==========================================
+ Coverage   95.74%   97.93%   +2.19%     
==========================================
  Files         102      102              
  Lines        6885     6926      +41     
==========================================
+ Hits         6592     6783     +191     
+ Misses        293      143     -150     

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[tatiana]

Hi @YourRoyalLinus — thanks so much for following up and further improving the solution! The implementation itself, along with the documentation and tests, is very thorough.

I also noticed a bug that prevents the cache from invalidating when a DAG initially swaps LoadModes from DBT_LS to `DBT_MANIFEST or vice versa. The fix is extremely small (8 simple loc + 2 new unit tests).

Would you prefer a separate issue and PR for tracking, or is there a threshold that's small enough to lump those changes into this PR? My preference is to separate them, for many reasons, but I don't want to pile on new issues and PRs unnecessarily.

A separate PR for this fix would be great.

If you could address the minor comment I left and rebase this PR, I'm happy to approve it once the checks pass. We can release this as part of the next Cosmos release, likely 1.13.1 or 1.14.0.

[tatiana]

Looks great, @YourRoyalLinus , thank you!

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

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[tatiana]

I'm merging since the check that failed is unrelated to the changes in this PR, thanks a lot, @YourRoyalLinus !