Fix: xr_engine strict vs. aux_coords

[pawel-wolff]

Description

This PR fixes the xr_engine handling of the aux_coords and strict arguments.

Changes

• Invalid auxiliary coordinates are now handled consistently with the value of strict.

• When an entry in aux_coords references a dimension that is not present in the dataset (e.g. aux_coords={"my_aux_coord": ("metadata_key", "unknown_dimension")}):

  • If strict=True, a ValueError is raised.
  • If strict=False, the invalid auxiliary coordinate is silently ignored.

Motivation

Allowing invalid auxiliary coordinates to be ignored when strict=False is particularly useful when using split_dims. In that case, an auxiliary coordinate may only be applicable to a subset of the datasets produced by the split, while being invalid for the others.

Tests

Added test coverage for both strict=True and strict=False behaviors, including a split_dims use case demonstrating that dataset-specific auxiliary coordinates are handled correctly.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.44%. Comparing base (a0d6492) to head (d89e54f).
⚠️ Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1030      +/-   ##
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+ Coverage    82.43%   82.44%   +0.01%     
===========================================
  Files          237      237              
  Lines        16683    16698      +15     
  Branches       806      808       +2     
===========================================
+ Hits         13752    13767      +15     
  Misses        2694     2694              
  Partials       237      237              

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