Shapely buffer returns empty polygon

[sor-droneup]

Expected behavior and actual behavior.

I'm using a buffer to reduce precision error before applying contains operation on my geometries. Geometry that is expected to contain another one gets small buffer applied to catch a cases when there is some rounding issue eg. -85.1234 and -85.123400000000055.

However some polygons after having this operation applied returns empty geometry:

example polygon:
POLYGON ((-8486160.859752608 4407005.311912118, -8486322.012133999 4419552.266313265, -8498821.965759974 4419382.682467878, -8498646.158633558 4406836.479565462, -8486160.859752608 4407005.311912118))

buffer(1e-9) - ok
buffer(1e-10) - ok
buffer(1e-11) - POLYGON EMPTY

Steps to reproduce the problem.

wkt = "POLYGON ((-8486160.859752608 4407005.311912118, -8486322.012133999 4419552.266313265, -8498821.965759974 4419382.682467878, -8498646.158633558 4406836.479565462, -8486160.859752608 4407005.311912118))"
poly = shapely.wkt.loads(wkt)
print(poly.buffer(1e-11))

Operating system

Alpine (docker image - ghcr.io/osgeo/gdal:alpine-small-3.8.2)

Shapely version and provenance

shapely - 2.0.3 installed through poetry

[theroggy]

In some rare cases this indeed happens when a negative buffer is applied :-(.

Shapely is actually mainly a python wrapper around a C++ library, GEOS, where the actual algorithms are implemented. So I added this example to an existing issue about this problem in the GEOS project: libgeos/geos#984