Adds ValueError to mapbase.submap() when Helioprojection coordinate contains NaN values.

changelog/7543.feature.rst

@@ -0,0 +1 @@
+Updated :meth:`sunpy.map.Map.submap` to check if it is about to work on locations with NaNs now errors and informs the user that they likely want to use :meth:`~sunpy.coordinates.Helioprojective.assume_spherical_screen` so that the off-disk 2D coordinate can be converted to a 3D coordinate.

sunpy/map/mapbase.py

@@ -36,7 +36,7 @@
 import sunpy.coordinates
 import sunpy.visualization.colormaps
 from sunpy import config, log
-from sunpy.coordinates import HeliographicCarrington, get_earth, sun
+from sunpy.coordinates import HeliographicCarrington, Helioprojective, get_earth, sun
 from sunpy.coordinates.utils import get_rectangle_coordinates
 from sunpy.image.resample import resample as sunpy_image_resample
 from sunpy.image.resample import reshape_image_to_4d_superpixel
@@ -1994,6 +1994,18 @@ def _parse_submap_quantity_input(self, bottom_left, top_right, width, height):
     @_parse_submap_input.register(SkyCoord)
     @_parse_submap_input.register(BaseCoordinateFrame)
     def _parse_submap_coord_input(self, bottom_left, top_right, width, height):
+        msg = (
+            "The {quadrant} input contains NaN values. "
+            "It is possible the coordinates are off-disk. "
+            "Consider using Helioprojective.assume_spherical_screen"
+        )
+        if isinstance(bottom_left, Helioprojective):
+            if np.isnan(bottom_left.distance.to_value()).any():
+                raise ValueError(msg.format(quadrant="bottom_left"))
+        if top_right is not None and isinstance(top_right, Helioprojective):
+            if np.isnan(top_right.distance.to_value()).any():
+                raise ValueError(msg.format(quadrant="top_right"))
+
         # Use helper function to get top_right as a SkyCoord
         bottom_left, top_right = get_rectangle_coordinates(bottom_left,
                                                            top_right=top_right,

sunpy/map/tests/test_mapbase.py

@@ -25,7 +25,7 @@
 import sunpy.coordinates
 import sunpy.map
 import sunpy.sun
-from sunpy.coordinates import HeliographicCarrington, HeliographicStonyhurst, sun
+from sunpy.coordinates import HeliographicCarrington, HeliographicStonyhurst, Helioprojective, sun
 from sunpy.data.test import get_dummy_map_from_header, get_test_filepath
 from sunpy.image.transform import _rotation_registry
 from sunpy.map.mapbase import GenericMap
@@ -1815,3 +1815,19 @@ def test_plot_deprecated_positional_args(aia171_test_map):
     with pytest.warns(SunpyDeprecationWarning, match=r"Pass annotate=interpolation, axes=True as keyword args."):
         with pytest.raises(TypeError, match="non-boolean value"):
             aia171_test_map.plot('interpolation', True)
+
+
+def test_submap_nan_error_bottom_left(aia171_test_map):
+    h = Helioprojective([319, 2233]*u.arcsec, 0*u.arcsec, observer='earth', obstime='2020-04-08')
+    h_3d = h.make_3d()
+    with pytest.raises(ValueError, match="The bottom_left input contains NaN values."):
+        aia171_test_map.submap(h_3d)
+
+def test_submap_nan_error_top_right(aia171_test_map):
+    h = Helioprojective(319*u.arcsec, 0*u.arcsec, observer='earth', obstime='2020-04-08')
+    h2 = Helioprojective(2233*u.arcsec, 0*u.arcsec, observer='earth', obstime='2020-04-08')
+    h_3d = h.make_3d()
+    with pytest.warns(SunpyUserWarning, match="The conversion of these 2D helioprojective coordinates to 3D is all NaNs"):
+        h2_3d = h2.make_3d()
+    with pytest.raises(ValueError, match="The top_right input contains NaN values."):
+        aia171_test_map.submap(h_3d, top_right=h2_3d)