✨ feat(astro): gate unxts.parametric registrations on it being installed

[nstarman]

unxts.parametric is not a coordinaxs.astro dependency, but its ParametricQuantity is not a unxt.Q subclass either, so the AbstractDistance/Q promotion rules in coordinax.distances never reached it. The result depended on operand order:

Parallax(1, "mas") * PQ(1.0, "rad")   # ValueError: Parallax must have angular dimensions
PQ(1.0, "rad") * Parallax(1, "mas")   # PQ['solid angle'](..., unit='mas rad')

Same for DistanceModulus.

What this does

Adds the two missing promotion rules, in their own _src/register_parametric.py so the optional import is confined to one file, imported from _src/__init__ behind OptDeps.UNXTS_PARAMETRIC.installed.

OptDeps follows the optional-dependencies idiom unxt itself uses. It requires >=0.4.1: earlier versions keyed enum members on the installed version, so any two members sharing one silently collapsed into a single member reporting the wrong package's state — which caught every pair of uninstalled dependencies, and the co-released unxts.* packages (unxts.api, unxts.hypothesis and unxts.parametric are all 2.0.0). That is fixed in 0.4.1 (GalacticDynamics/optional_dependencies#57), so members can be added freely here.

unxts.parametric is declared as a [parametric] extra; the tests skip at module level on the same OptDeps check, so they run where the extra is installed and skip — not fail — where it is not.

Verification

• Both paths exercised: with the distribution hidden from importlib.metadata, coordinaxs.astro imports without pulling in unxts.parametric at all.
• Multi-member safety confirmed against the real packages: three unxts.* members at 2.0.0 plus two uninstalled ones all stay distinct.
• packages/coordinaxs.astro: 398 passed, 2 skipped. pre-commit clean.

Note

coordinax.distances.Distance has the identical gap (Distance * PQ raises the same way). A single add_promotion_rule(AbstractDistance, ParametricQuantity, ...) in core would close it for all three types, but core cannot import an optional package that only astro declares — it would need the same OptDeps treatment there. Left out of scope; happy to follow up.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes operand-order–dependent promotion behavior between coordinaxs.astro distance-like quantities (Parallax, DistanceModulus) and unxts.parametric.ParametricQuantity by adding explicit Plum promotion rules, while ensuring the registrations only load when unxts.parametric is actually installed.

Changes:

• Add OptDeps (based on optional-dependencies>=0.4.1) and gate unxts.parametric-specific registrations behind OptDeps.UNXTS_PARAMETRIC.installed.
• Register missing plum.add_promotion_rule promotions so Parallax/DistanceModulus interactions with ParametricQuantity reliably degrade to ParametricQuantity (order-independent).
• Add unit tests that skip when unxts.parametric isn’t installed, and add a [parametric] extra to coordinaxs.astro.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
uv.lock	Adds optional-dependencies to coordinaxs-astro, adds parametric extra (via unxts-parametric), and bumps optional-dependencies to 0.4.1.
pyproject.toml	Ensures workspace test group includes unxts.parametric so the gated registrations are exercised in CI when available.
packages/coordinaxs.astro/pyproject.toml	Adds hard dependency on optional-dependencies>=0.4.1 and declares [parametric] extra for unxts.parametric.
packages/coordinaxs.astro/src/coordinaxs/astro/_src/init.py	Conditionally imports the side-effect registration module when unxts.parametric is installed.
packages/coordinaxs.astro/src/coordinaxs/astro/_src/optional_deps.py	Introduces OptDeps enum for optional dependency checks.
packages/coordinaxs.astro/src/coordinaxs/astro/_src/register_parametric.py	Adds the two missing promotion rules to ParametricQuantity.
packages/coordinaxs.astro/tests/unit/distances/test_parametric_promotion.py	Adds regression tests for order-independent promotion and preserves existing degrade-to-u.Q behavior.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 7 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 6 changed files in this pull request and generated no new comments.

Suppressed comments (1)

packages/coordinaxs.astro/src/coordinaxs/astro/_src/init.py:16

• The conditional from .register_parametric import * is used only for its import side effects, and register_parametric.__all__ is empty, so the wildcard import never actually exports anything. This is confusing (and keeps a * import in the module) when a plain module import would be clearer and make the intent explicit.

if OptDeps.UNXTS_PARAMETRIC.installed:
    from .register_parametric import *

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.57%. Comparing base (f1eb540) to head (30a18e1).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #672   +/-   ##
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  Coverage   95.57%   95.57%           
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  Files         247      249    +2     
  Lines        8039     8052   +13     
=======================================
+ Hits         7683     7696   +13     
  Misses        356      356           

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