split plane center not as expected

[lalebarde]

In the following example, after the split, I expect the workplane to be in the plane of the split, but it looks like it is centered on the center of gravity of the remaining part, even if I call a workplane(centerOption="ProjectedOrigin"):

import cadquery as cq
from math import pi as pi, sin as sin, cos as cos, tan as tan, atan as atan
col_limon = (230, 153, 0, 0.5)

result0 = cq.Workplane("XY" ).box(100, 40, 20)
result = result0.faces(">Z").workplane().transformed(rotate=(90, 20, 0)).split(keepTop=True).workplane(centerOption="ProjectedOrigin").circle(20).extrude(20, combine = True)
show_object(result0, options=dict(rgba=col_limon))
show_object(result)

[lalebarde]

Possibly related, if after the split I call faces("<Z"), I expect it is relative to the workplane of the splitted part, but it is like "Z" is the world one:

result = result0.faces(">Z").workplane().transformed(rotate=(90, 20, -360/3*0)).split(keepTop=True).faces("<Z").workplane().circle(20).extrude(20, combine = True)

[lorenzncode]

The Workplane origin is where you expect it: (0, 0, 10.0).

split returned with the top object on the stack. Then when you create the circle it is created 'for each item on the stack' not the Workplane origin.

To create the circle at the origin you could use tags and create an empty Workplane:

import cadquery as cq

result0 = cq.Workplane("XY").box(100, 40, 20)

result = (
    result0.faces(">Z")
    .workplane()
    .transformed(rotate=(90, 20, 0))
    .tag("splitwp")
    .split(keepTop=True)
    .workplaneFromTagged("splitwp")
    .circle(20)
    .extrude(20, combine=True)
)

or call newObject with empty list:

import cadquery as cq

result0 = cq.Workplane("XY").box(100, 40, 20)

result = (
    result0.faces(">Z")
    .workplane()
    .transformed(rotate=(90, 20, 0))
    .split(keepTop=True)
    .newObject([])
    .circle(20)
    .extrude(20, combine=True)
)

For debug, you can break the chain after the split and inspect the stack.:

import cadquery as cq

result0 = cq.Workplane("XY").box(100, 40, 20)

result = (
    result0.faces(">Z")
    .workplane()
    .transformed(rotate=(90, 20, 0))
    .split(keepTop=True)
    )

print(result.vals())         # note stack is not empty
print(result.val().Center()) # this is where the circle would be centered if you do not clear the stack