Test hardening of dbt node having tags as unset or missing

[pankajkoti]

Follow-up PR for #1915 adding tests to ensure cosmos handles well when dbt tags are missing or set to None on a DbtNode.

related: #1915
closes: #1919

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Name	Link
🔨 Latest commit	89ae417
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[pankajkoti]

We observed test failures here before rebasing main (i.e. before PR #1915 was merged): https://github.com/astronomer/astronomer-cosmos/actions/runs/16935353240/job/47990492166?pr=1918

[Copilot]

Pull Request Overview

This PR adds test coverage to ensure that the cosmos dbt graph loader properly handles edge cases when the tags field is either missing or set to None in dbt manifest nodes. This hardening follows up on PR #1915 to prevent potential issues when processing malformed or incomplete dbt manifests.

• Adds parameterized tests for handling None and missing tags fields in dbt manifest nodes
• Introduces a helper function to create minimal test manifests with configurable tag values
• Implements a sentinel object pattern to distinguish between missing keys and None values

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[pankajkoti]

After rebasing PR #1915, we still have the test failing: https://github.com/astronomer/astronomer-cosmos/actions/runs/16935513205/job/47991044286?pr=1918#step:6:1083, which is when the tags key is present but set to None. To fix this, I have pushed a commit: 89ae417

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.08%. Comparing base (e5a90eb) to head (89ae417).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1918   +/-   ##
=======================================
  Coverage   98.08%   98.08%           
=======================================
  Files          86       86           
  Lines        5334     5334           
=======================================
  Hits         5232     5232           
  Misses        102      102           

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[tatiana]

Thanks a lot, @pankajkoti , looks great!