Invalid number of points in LinearRing

[Ryszard-Trojnacki]

I'm trying to create LinearRing (Polygon) from array of CoordinatesXY but I get exception:
IllegalArgumentException: Invalid number of points in LinearRing (found 3 - must be 0 or >= 4)

Why there is a minimum of 4 points? Isn't triangle a valid LinearRing?

Another thing - Java implementation (JTS) requires only 3 points.

JavaScript constant definition and validate method:

LinearRing.MINIMUM_VALID_SIZE = 4

validateConstruction() {
    if (!this.isEmpty() && !super.isClosed.call(this)) 
      throw new IllegalArgumentException('Points of LinearRing do not form a closed linestring')
    
    if (this.getCoordinateSequence().size() >= 1 && this.getCoordinateSequence().size() < LinearRing.MINIMUM_VALID_SIZE) 
      throw new IllegalArgumentException('Invalid number of points in LinearRing (found ' + this.getCoordinateSequence().size() + ' - must be 0 or >= 4)')
    
  }

Java constant definition and validate method:

public class LinearRing extends LineString {
  public static final int MINIMUM_VALID_SIZE = 3;

  private void validateConstruction() {
    if (!isEmpty() && ! super.isClosed()) {
      throw new IllegalArgumentException("Points of LinearRing do not form a closed linestring");
    }
    if (getCoordinateSequence().size() >= 1 && getCoordinateSequence().size() < MINIMUM_VALID_SIZE) {
      throw new IllegalArgumentException("Invalid number of points in LinearRing (found "
      		+ getCoordinateSequence().size() + " - must be 0 or >= " + MINIMUM_VALID_SIZE + ")");
    }
  }
}

Shouldn't this be changed to 3 like in Java code?

[Ryszard-Trojnacki]

I see that in Java this code was changed from 4 to 3.

My workaround is to add this to override minimum valid size:

LinearRing.MINIMUM_VALID_SIZE=3;

[bjornharrtell]

@Ryszard-Trojnacki I guess the definition is that it needs to be a closed ring in which case a triangle would be defined by 4 points. As seen in the pull request in JTS it was lowered with the intent to be able to create invalid rings.