Add warning for non-homogenous case

glue_astronomy/translators/spectrum1d.py

@@ -1,4 +1,5 @@
 import numpy as np
+import warnings
 
 from glue.config import data_translator
 from glue.core import Data, Subset
@@ -157,9 +158,7 @@ def _has_homogenous_spectral_solution(self, data):
 
     def to_data(self, obj):
 
-        # Glue expects spectral axis first for cubes (opposite of specutils).
-        # Swap the spectral axis to first here. to_object doesn't need this because
-        # Spectrum1D does it automatically on initialization.
+        # specutils 2.0 doesn't care where the spectral axis anymore, but we still need PaddedSpectrumWCS for now
         if obj.flux.ndim > 1 and obj.wcs.world_n_dim == 1:
             data = Data(coords=PaddedSpectrumWCS(obj.wcs, obj.flux.ndim, obj.spectral_axis_index))
         else:
@@ -238,10 +237,13 @@ def to_object(self, data_or_subset, attribute=None, statistic='mean'):
                     kwargs = {'spectral_axis': spectral_axis}
 
                 else:
-                    # In this case we'll need to resample the flux onto a common spectral axis before collapsing
+                    # In this case we should resample the flux onto a common spectral axis before collapsing
+                    warnings.warn("Spectral solution is not the same at all spatial points,"
+                                  " collapsing may give inaccurate results.")
                     kwargs = {'wcs': data.coords}
             else:
-                raise ValueError('Can only use statistic= if the Data object has a FITS WCS')
+                # Shouldn't get here anymore, but just in case.
+                raise ValueError('Can only use statistic= if the Data object has a GWCS or FITS WCS')
 
         elif isinstance(data.coords, SpectralCoordinates):