If shape_out is specified, use this over the array_shape attribute of a WCS object

reproject/tests/test_utils.py

@@ -5,6 +5,7 @@
 from astropy.utils.data import get_pkg_data_filename
 from astropy.wcs import WCS
 
+from reproject.conftest import set_wcs_array_shape
 from reproject.tests.helpers import assert_wcs_allclose
 from reproject.utils import parse_input_data, parse_input_shape, parse_output_projection
 from reproject.wcs_utils import has_celestial
@@ -92,6 +93,26 @@ def test_parse_output_projection_invalid_wcs(simple_celestial_fits_wcs):
         parse_output_projection(simple_celestial_fits_wcs)
 
 
+def test_parse_output_projection_override_shape_out(simple_celestial_wcs):
+    # Regression test for a bug that caused shape_out to be ignored if the
+    # WCS object had array_shape set - but shape_out should override the WCS
+    # shape.
+
+    wcs_ref = simple_celestial_wcs
+
+    set_wcs_array_shape(wcs_ref, (10, 20))
+
+    if hasattr(wcs_ref, "low_level_wcs"):
+        assert wcs_ref.low_level_wcs.array_shape == (10, 20)
+    else:
+        assert wcs_ref.array_shape == (10, 20)
+
+    wcs, shape = parse_output_projection(wcs_ref, shape_out=(30, 40))
+
+    assert shape == (30, 40)
+    assert_wcs_allclose(wcs, wcs_ref)
+
+
 @pytest.mark.filterwarnings("ignore::astropy.utils.exceptions.AstropyUserWarning")
 @pytest.mark.filterwarnings("ignore::astropy.wcs.wcs.FITSFixedWarning")
 def test_has_celestial():

reproject/utils.py

@@ -166,12 +166,13 @@ def parse_output_projection(output_projection, shape_in=None, shape_out=None, ou
             wcs_out = HighLevelWCSWrapper(output_projection)
         else:
             wcs_out = output_projection
-        if wcs_out.low_level_wcs.array_shape is not None:
-            shape_out = wcs_out.low_level_wcs.array_shape
-        elif shape_out is None:
-            raise ValueError(
-                "Need to specify shape_out when specifying output_projection as WCS object"
-            )
+        if shape_out is None:
+            if wcs_out.low_level_wcs.array_shape is not None:
+                shape_out = wcs_out.low_level_wcs.array_shape
+            else:
+                raise ValueError(
+                    "Need to specify shape_out when specifying output_projection as WCS object"
+                )
     elif isinstance(output_projection, str):
         hdu_list = fits.open(output_projection)
         shape_out = hdu_list[0].data.shape