2d planar wire extrusion on coincident start & finish

[fragmuffin]

Problem

2d wires with coincident start & finish points cannot be generated without using .close() to create the last linear wire.

Using .close() imposes a mandatory linear line somewhere on the wire.

Positive Test

The following code functions as I'd expect; extruding a triangle into a 3d solid

import cadquery
from Helpers import show

obj = cadquery.Workplane('XY') \
    .moveTo(0, 0).lineTo(1, 0).lineTo(0, 1) \
    .close() \
    .extrude(1)

show(obj)

Reproducing Erroneous Behaviour

The following are small changes to the above definition of obj

1) Manually closing yields no solid

obj = cadquery.Workplane('XY') \
    .moveTo(0, 0).lineTo(1, 0).lineTo(0, 1) \
    .lineTo(0, 0) \
    .extrude(1)

no solid is generated

edit: no longer considered a bug 👍 ;
wires are not expected to be automatically closed, so a coincident point on a wire does not automatically imply that it is closed.

2) Closing on coincidental point

obj = cadquery.Workplane('XY') \
    .moveTo(0, 0).lineTo(1, 0).lineTo(0, 1) \
    .lineTo(0, 0).close() \
    .extrude(1)

raises exception: Line through identic points

3) Closing on coincidental point (arcs)

thickness = 3.
length = 10.
width = 5.

obj = cadquery.Workplane('XY', origin=(0, 0, -thickness / 2)) \
    .moveTo(length / 2, 0) \
    .threePointArc(
        (0, width / 2), (-length / 2, 0)
    ) \
    .threePointArc(
        (0, -width / 2), (length / 2, 0)
    ) \
    .close().extrude(thickness)

raises exception: BRepAdaptor_Curve::No geometry

Impossible Solid?

There are usually ways to get around this limitation, but I found the following solid impossible to create

I ended up creating it in 2 halves, then union both sides.

[dcowden]

Can't find it now, but there has been a lot of discussion on this. It came up when working on dxf import.... It's desirable to get the code the creates the wires from edges separated .

Last I remember, I think I decided that instead of pushing wires onto the pending wires list, we should just collect all of the edges together and form wires in extrude.

[fragmuffin]

I imagine any re-design of forming 2d wires will impact #172. Perhaps this could be the first step toward parametric 2d sketches.

[adam-james-v]

I often end up doing the same thing. It's a workaround in my opinion.

I think that it would be useful to add logic to close(). If the set of edges / wires is open, then add a line to close it, otherwise, just return a single wire and work with that directly.

It might be as simple as checking if start point = end point and doing nothing if that's true...

Or maybe it's way more difficult. That's just a first thought

[fragmuffin]

As agreed in #257#issuecomment-385205989, test 1 is not a failed test-case.
So after #257 is merged, I think this issue can be closed

[gntech]

#257 have been merged now