pyproj 2.1.3 transform() fails with errcheck=True

[cjmayo]

#228 introduced a check for the return value of proj_trans_generic which is saved as err_count although it is described as "Number of transformations completed" in PROJ:
https://github.com/OSGeo/proj.4/blob/e87b3744350baca2b7fe35070e621a6b45bcbf67/src/4D_api.cpp#L353

(proj_trans_array returns 0 if all coordinates are transformed without error, otherwise returns an error number:
https://github.com/OSGeo/proj.4/blob/e87b3744350baca2b7fe35070e621a6b45bcbf67/src/4D_api.cpp#L282)

This code:

from pyproj import Proj, transform

p1 = Proj(init="epsg:4326")
p2 = Proj(init="epsg:27700")

print(transform(p1, p2, 1.716073972, 52.658007833, errcheck=True))

now fails with:

  File "/usr/lib/python3.7/site-packages/pyproj/transformer.py", line 367, in transform
    xx=x, yy=y, zz=z, tt=tt, radians=radians, errcheck=errcheck
  File "/usr/lib/python3.7/site-packages/pyproj/transformer.py", line 180, in transform
    inx, iny, inz=inz, intime=intime, radians=radians, errcheck=errcheck
  File "pyproj/_transformer.pyx", line 144, in pyproj._transformer._Transformer._transform
pyproj.exceptions.ProjError: 1 proj_trans_generic error(s)

As per this comment #208 (comment), a return value of 0 may be an error (or just there was nothing to transform).
But you would expect a positive integer result on a successful transformation as above?

[snowman2]

@kbevers, can you clarify this?

[snowman2]

Nevermind, this is correct. I misinterpreted this and is a bug.