Unexpected result transforming lat-lon on sphere to WGS84

[andypbarrett]

I am trying to convert lat, lon on a sphere to lat, lon on the WGS84 ellipsoid. My understanding is that latitude, at least, should be different. However, I get the output is the same as the input.

In [1]: import pyproj                                                                                                                                                                                       
In [2]: pyproj.__version__                                                                                                                                                                                  
Out[2]: '2.6.1.post1'

In [3]: from pyproj import Transformer                                                                                                                                                                      
In [4]: tranformer = Transformer.from_crs('+proj=lonlat +ellps=sphere +R=6367470', 4326, always_xy=True)                                                                                                    
In [5]: tranformer.transform(10., 60.)                                                                                                                                                                      
Out[5]: (10.0, 60.0)
In [6]: tranformer.transform(10., 89.)                                                                                                                                                                      
Out[6]: (10.0, 89.0)

[snowman2]

Looks like it is a noop transformation:

>>> from pyproj import Transformer
>>> tranformer = Transformer.from_crs('+proj=lonlat +ellps=sphere +R=6367470', 4326, always_xy=True)
>>> tranformer
<Concatenated Operation Transformer: noop>
Description: Ballpark geographic offset from unknown to WGS 84 + axis order change (2D)
Area of Use:
- name: World
- bounds: (-180.0, -90.0, 180.0, 90.0)

projinfo -s '+proj=lonlat +ellps=sphere +R=6367470 +type=crs' -t 'EPSG:4326' -o PROJ
Candidate operations found: 1
-------------------------------------
Operation No. 1:

unknown id, Ballpark geographic offset from unknown to WGS 84, unknown accuracy, World, has ballpark transformation

PROJ string:
+proj=axisswap +order=2,1

I would ask here if you think this behavior is incorrect: /~https://github.com/osgeo/PROJ/

UPDATE: Better answer here: OSGeo/PROJ#2860

[andypbarrett]

See the answer here: OSGeo/PROJ#2860