style: fix ruff lint and format findings in polarized-sky code

Author: kartikmandar

src/matvis/core/coherency.py

@@ -483,7 +483,7 @@ def partition_and_negate(stokes, skycoords, I_sky=None):
     if len(idx_M) > 0:
         raise ValueError(
             "partition_and_negate is only valid when no sources have "
-            "mixed-sign eigenvalues; got {} mixed sources.".format(len(idx_M))
+            f"mixed-sign eigenvalues; got {len(idx_M)} mixed sources."
         )
     perm = np.concatenate([idx_P, idx_N])
     n_P = int(len(idx_P))

src/matvis/wrapper.py

@@ -168,9 +168,7 @@ def simulate_vis(
     fnc = gpu.simulate if use_gpu else cpu.simulate
 
     if (fluxes is None) == (stokes is None):
-        raise ValueError(
-            "Provide exactly one of `fluxes` or `stokes` to simulate_vis."
-        )
+        raise ValueError("Provide exactly one of `fluxes` or `stokes` to simulate_vis.")
 
     if polarized is None:
         polarized = stokes is not None

tests/test_coherency.py

@@ -1,8 +1,7 @@
 """Unit tests for coherency matrix and M matrix computation."""
 
-import pytest
-
 import numpy as np
+import pytest
 
 from matvis.core.coherency import (
     coherency_to_stokes,

tests/test_compare_pyuvsim.py

@@ -89,7 +89,7 @@ def test_compare_pyuvsim(polarized, use_analytic_beam):
     ids=["analytic_beam", "uvbeam"],
 )
 def test_compare_pyuvsim_polarized_sky(use_analytic_beam, xfail):
-    """matvis stokes path vs pyuvsim for a fully polarized sky (Q,U,V≠0).
+    """Compare the matvis stokes path with pyuvsim for a fully polarized sky (Q,U,V≠0).
 
     The existing ``test_compare_pyuvsim`` only exercises Stokes I; this one
     drives non-trivial coherency rotation and XY/YX off-diagonals through

tests/test_polarized_benchmark.py

@@ -3,17 +3,18 @@
 Not run in CI — use: pytest tests/test_polarized_benchmark.py -v -s
 """
 
-import pytest
-
 import os
 
+import pytest
+
 pytestmark = pytest.mark.skipif(
     not os.getenv("RUN_BENCHMARKS"),
     reason="Set RUN_BENCHMARKS=1 to run benchmarks",
 )
 
-import numpy as np
 import time
+
+import numpy as np
 from astropy import units as un
 from astropy.coordinates import EarthLocation
 from astropy.time import Time

tests/test_polarized_sky.py

@@ -5,9 +5,8 @@
 - New path: simulate_vis(stokes=...) with full Stokes params
 """
 
-import pytest
-
 import numpy as np
+import pytest
 from astropy import units as un
 from astropy.coordinates import EarthLocation, SkyCoord
 from astropy.time import Time
@@ -54,8 +53,11 @@ def _make_sim_params(nsrc=10, nant=3, ntime=2, nfreq=1, precision=2):
 
 
 class TestBackwardCompatibility:
-    """``stokes=[I,0,0,0]`` routed through the eigen path must reproduce
-    the legacy ``fluxes``-only path that uses ``sqrt(0.5*I)`` directly."""
+    """Check that the eigen path reproduces the legacy unpolarized path.
+
+    ``stokes=[I,0,0,0]`` routed through the eigen path must reproduce
+    the legacy ``fluxes``-only path that uses ``sqrt(0.5*I)`` directly.
+    """
 
     @pytest.mark.parametrize("precision,atol", [(2, 1e-12), (1, 1e-4)])
     def test_unpolarized_stokes_matches_existing(self, precision, atol):
@@ -138,8 +140,11 @@ class TestNegativeFluxHandling:
         ["positive_sky", "mixed_negative_sky"],
     )
     def test_negative_flux_path(self, case):
-        """Sign-split route must match eigen when sky is positive, and
-        produce finite nonzero visibilities when some Stokes I are negative."""
+        """Check the sign-split route against the eigen route.
+
+        Sign-split must match eigen when the sky is positive, and
+        produce finite nonzero visibilities when some Stokes I are negative.
+        """
         params = _make_sim_params(nsrc=10, nant=3, ntime=2, nfreq=1)
 
         if case == "positive_sky":
@@ -246,10 +251,14 @@ def test_negate_source_symmetry(self):
 
 
 class TestPolarizedInference:
-    """Passing ``stokes`` must auto-enable ``polarized``; explicit
-    ``polarized=False`` alongside ``stokes`` must raise."""
+    """Check that ``polarized`` is correctly inferred from ``stokes``.
+
+    Passing ``stokes`` must auto-enable ``polarized``; explicit
+    ``polarized=False`` alongside ``stokes`` must raise.
+    """
 
     def test_stokes_alone_enables_polarized(self):
+        """Omitting ``polarized`` while passing ``stokes`` must auto-enable it."""
         params = _make_sim_params(nsrc=5, nant=2, ntime=1, nfreq=1)
         nsrc = len(params["ra"])
         nfreq = len(params["freqs"])
@@ -264,6 +273,7 @@ def test_stokes_alone_enables_polarized(self):
         assert not np.any(np.isnan(vis))
 
     def test_polarized_false_with_stokes_raises(self):
+        """Explicit ``polarized=False`` alongside ``stokes`` must raise."""
         params = _make_sim_params(nsrc=5, nant=2, ntime=1, nfreq=1)
         nsrc = len(params["ra"])
         nfreq = len(params["freqs"])