Polygonizer throws NullPointerException

[clarisma]

Polygonization throws NullPointerException using the following input geometry:

MULTILINESTRING ((143145039 659338416, 143146736 659338410, 143146496 659332192, 143152064 659332033, 143151920 659338391, 143153808 659338383, 143153951 659330368, 143144624 659330497, 143145039 659338416),
(143146736 659338410, 143151920 659338391, 143152064 659332033, 143146496 659332192, 143146736 659338410))

java.lang.NullPointerException: Cannot read field "y" because "p" is null
at org.locationtech.jts.algorithm.locate.IndexedPointInAreaLocator.locate(IndexedPointInAreaLocator.java:88)
at org.locationtech.jts.operation.polygonize.EdgeRing.isInRing(EdgeRing.java:261)
at org.locationtech.jts.operation.polygonize.EdgeRing.findEdgeRingContaining(EdgeRing.java:87)
at org.locationtech.jts.operation.polygonize.HoleAssigner.findShellContaining(HoleAssigner.java:106)
at org.locationtech.jts.operation.polygonize.HoleAssigner.assignHoleToShell(HoleAssigner.java:78)
at org.locationtech.jts.operation.polygonize.HoleAssigner.assignHolesToShells(HoleAssigner.java:72)
at org.locationtech.jts.operation.polygonize.HoleAssigner.assignHolesToShells(HoleAssigner.java:40)
at org.locationtech.jts.operation.polygonize.Polygonizer.polygonize(Polygonizer.java:255)
at org.locationtech.jts.operation.polygonize.Polygonizer.getGeometry(Polygonizer.java:188)

I can work around this issue by unioning the geometry prior to passing it to the Polygonizer.

[dr-jts]

That linework is not fully noded, as required by Polygonizer. But it should throw a more informative exception.

[dr-jts]

Fixed by #692

[clarisma]

Thanks for the fast fix, I'll have a look at it tomorrow.
Could you explain the "not fully noded" part? The two linestrings polygonize fine individually. The four vertexes of the squarish shape are shared by the outer U-shape; their edges don't cross. I know I'm missing something, but I can't figure out what.

[dr-jts]

Input to the Polygonizer must touch only at endpoints (nodes). These lines clearly violate that.

Note that this also precludes input lines which share lines segments (or subsegments). This data also violates that.

[clarisma]

Yes, I figured the collinear edges might be the issue.
However, this geometry has shared segments as well, but produces two valid polygons:

MULTILINESTRING ((100 100, 200 100, 200 200, 100 200, 100 100),
(200 100, 300 100, 300 200, 200 200, 200 100))

[dr-jts]

Invalid input may still produce valid output. But it also may not....

With the fix for this issue, in fact the data above also produces valid output.

But these examples are outside the operating range of Polygonizer, so all bets are off.