use ndarray comparison options in wcs comparison

CHANGES.rst

@@ -30,6 +30,9 @@ general
 
 - Use tolerance for more comparisons in ``compare_asdf`` [#917]
 
+- Use array comparison options (including ``nan`` equality) when
+  comparing ``WCS`` objects during ``compare_asdf`` [#941]
+
 ramp_fitting
 ------------
 

romancal/regtest/regtestdata.py

@@ -633,26 +633,22 @@ def _wcs_to_ra_dec(wcs):
     return wcs(x, y)
 
 
-class WCSOperator(BaseOperator):
+class WCSOperator(NDArrayTypeOperator):
     def give_up_diffing(self, level, diff_instance):
         # for comparing wcs instances this function evaluates
         # each wcs and compares the resulting ra and dec outputs
         # TODO should we compare the bounding boxes?
         ra_a, dec_a = _wcs_to_ra_dec(level.t1)
         ra_b, dec_b = _wcs_to_ra_dec(level.t2)
-        meta = {}
-        for name, a, b in [("ra", ra_a, ra_b), ("dec", dec_a, dec_b)]:
-            # TODO do we want to do something fancier than allclose?
-            if not np.allclose(a, b):
-                meta[name] = {
-                    "abs_diff": np.abs(a - b),
-                }
-        if meta:
-            diff_instance.custom_report_result(
-                "wcs_differ",
-                level,
-                meta,
-            )
+        ra_diff = self._compare_arrays(ra_a, ra_b)
+        dec_diff = self._compare_arrays(dec_a, dec_b)
+        difference = {}
+        if ra_diff:
+            difference["ra"] = ra_diff
+        if dec_diff:
+            difference["dec"] = dec_diff
+        if difference:
+            diff_instance.custom_report_result("wcs_differ", level, difference)
         return True
 
 
@@ -712,7 +708,7 @@ def compare_asdf(result, truth, ignore=None, rtol=1e-05, atol=1e-08, equal_nan=T
         ),
         TimeOperator(types=[astropy.time.Time]),
         TableOperator(rtol, atol, equal_nan, types=[astropy.table.Table]),
-        WCSOperator(types=[gwcs.WCS]),
+        WCSOperator(rtol, atol, equal_nan, types=[gwcs.WCS]),
     ]
     # warnings can be seen in regtest runs which indicate
     # that ddtrace logs are evaluated at times after the below

romancal/regtest/test_regtestdata.py

@@ -5,14 +5,23 @@
 from roman_datamodels import datamodels as rdm
 from roman_datamodels import maker_utils
 
+from romancal.assign_wcs.assign_wcs_step import load_wcs
 from romancal.regtest.regtestdata import compare_asdf
 
 
+def _add_wcs(tmp_path, model):
+    dfn = tmp_path / "wcs_distortion.asdf"
+    distortion_model = rdm.DistortionRefModel(maker_utils.mk_distortion())
+    distortion_model.save(dfn)
+    load_wcs(model, {"distortion": dfn})
+
+
 @pytest.mark.parametrize("modification", [None, "small", "large"])
 def test_compare_asdf(tmp_path, modification):
     fn0 = tmp_path / "test0.asdf"
     fn1 = tmp_path / "test1.asdf"
     l2 = rdm.ImageModel(maker_utils.mk_level2_image(shape=(100, 100)))
+    _add_wcs(tmp_path, l2)
     l2.save(fn0)
     atol = 0.0001
     if modification == "small":