REGRESSION: ring geometrically not-closed on 3D topology

[amsilva]

When adding an edge to the topology with totopogeom sometimes it gives this error "Corrupted topology: ring of edge x is geometrically not-closed".

I reduced the problem to an example with two lines. The first line is added with no errors to the topology but the second one throws this error. The second line intersects with the first one, but there's no vertex on the intersection. (example attached)

This bug results of a postgis-user ​post where Sandro Santilli confirmed the bug and complemented with this:

Gory details: the problem likely lays in _lwt_MakeRingShell which was recently changed to NOT use GEOS but rather do things internally, to reduce overhead. The internal implementation is NOT dropping the Z as the geos implementation did.

[strk]

Version 3.1.7 (and 3.1 branch at time of writing) is also affected. Reduced testcase:

BEGIN;
SELECT NULL FROM topology.createtopology('b5234', 0, 0, TRUE);
SELECT 'b5234.0', TopoGeo_addLinestring('b5234',
  'LINESTRING(0 0 0, 10 0 1, 10 10 3)', 0);
SELECT 'b5234.1', TopoGeo_addLinestring('b5234',
  'LINESTRING(10 10 3, 5 0 0.8)', 0);
ROLLBACK;

[strk]

3.0.8dev (current stable-3.0 branch) is also affected, while I confirm 3.0.1 works.

[strk]

The regression was introduced in version 3.0.2 via commit [273b7eaad3e9a6dfae8eef9e29f78dd67582a4ca/git] which references ticket #4709

[Sandro Santilli <strk@…>]

In 41a87d3/git:

Fix 2.5d topology building regression (geometrically non-closed)

References #5234 in master branch (3.4.0dev)

[Sandro Santilli <strk@…>]

In 642c8332/git:

Fix 2.5d topology building regression (geometrically non-closed)

References #5234 in 3.3 branch (3.3.2dev)

[Sandro Santilli <strk@…>]

In 7f5f964/git:

Fix 2.5d topology building regression (geometrically non-closed)

References #5234 in 3.2 branch (3.2.4dev)

[Sandro Santilli <strk@…>]

In 61bb7f6/git:

Fix 2.5d topology building regression (geometrically non-closed)

References #5234 in 3.1 branch (3.1.8dev)

[Sandro Santilli <strk@…>]

In f96b813/git:

Fix 2.5d topology building regression (geometrically non-closed)

Closes #5234 in 3.0 branch (3.0.8dev)