Fix wcs.array_shape definition in WcsGeom.create

[QRemy]

Fix wcs.array_shape definition in WcsGeom.create to fix the bug described in :
#4652 (comment)

[Astro-Kirsty]

Thanks @QRemy.
Are the tests failing because of the known CI issue, or because this reverses the order where we have no implemented that before?

[registerrier]

Thanks @QRemy . I am afraid the problems run deeper.

For instance, the get_shape function used in WcsGeom.create handles differently tuples and lists.

See:

>>> print(WcsGeom.create(binsz=(0.1,0.05)).wcs)
WCS Keywords

Number of WCS axes: 2
CTYPE : 'RA---CAR'  'DEC--CAR'  
CRVAL : 0.0  0.0  
CRPIX : 1800.5  1800.5  
PC1_1 PC1_2  : 1.0  0.0  
PC2_1 PC2_2  : 0.0  1.0  
CDELT : -0.1  0.05  
NAXIS : 3600  3600

but:

>>> print(WcsGeom.create(binsz=[0.1,0.05]).wcs)
WCS Keywords

Number of WCS axes: 2
CTYPE : 'RA---CAR'  'DEC--CAR'  
CRVAL : 0.0  0.0  
CRPIX : 1800.5  900.5  
PC1_1 PC1_2  : 1.0  0.0  
PC2_1 PC2_2  : 0.0  1.0  
CDELT : -0.1  0.1  
NAXIS : 1800  3600

EDIT: actually, this is probably the intended behaviour, because lists can define different bin size along non-spatial axes. I think this should be better protected since here there is no non-spatial axis.

[registerrier]

According to https://astropy-astrofrog.readthedocs.io/en/latest/api/astropy.wcs.WCS.html#astropy.wcs.WCS.array_shape

the expected order is (rows, columns). It should then be reversed as you propose.

[QRemy]

The previous tests failures were related to a mismatch between the width of the region geom and their wcs array_shape, I added a fix to have this consistent.

[codecov]

Codecov Report

Merging #4677 (78fa8d1) into main (60f03ad) will increase coverage by 0.00%.
The diff coverage is 86.66%.

@@           Coverage Diff           @@
##             main    #4677   +/-   ##
=======================================
  Coverage   75.95%   75.96%           
=======================================
  Files         223      223           
  Lines       31959    31969   +10     
=======================================
+ Hits        24275    24284    +9     
- Misses       7684     7685    +1     

Files Changed	Coverage Δ
gammapy/modeling/models/tests/test_core.py	79.74% <0.00%> (ø)
gammapy/maps/wcs/geom.py	95.93% <83.33%> (-0.19%)	⬇️
gammapy/maps/region/geom.py	91.06% <100.00%> (+0.05%)	⬆️
gammapy/maps/wcs/tests/test_geom.py	100.00% <100.00%> (ø)

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[registerrier]

Thanks @QRemy. Looks good. See few inline comments.

[registerrier]

Is this needed here? Why does it need to be re-created?

[registerrier]

Thanks @QRemy . Merging now.