[postgis-tickets] [PostGIS] #5105: TopoGeo_addLineString turns topology invalid

[PostGIS]

#5105: TopoGeo_addLineString turns topology invalid
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  Reporter:  strk      |      Owner:  strk
      Type:  defect    |     Status:  new
  Priority:  medium    |  Milestone:  PostGIS 3.3.0
 Component:  topology  |    Version:  master
Resolution:            |   Keywords:  reliability
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Comment (by strk):

 On a closer look, the "face has multiple shells" seems to be a false
 invalidity, as the reported "shell" is actually a ring formed only by
 dangling edges. The Topology validation code is using
 `ST_IsPolygonCCW(ST_MakePolygon($ringedges))` to determine if the ring is
 a shell, erroneously expecting that a "flat" ring would always return
 false from ST_IsPolygonCCW but this is evidently not the case.

 The manual does not mention any explicit handling of such cases, I'd think
 a NULL could be returned, or what other options do you see ?
 https://postgis.net/docs/ST_IsPolygonCCW.html

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5105#comment:4>
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