SVGLoader pointsToStroke incorrect result using linecap square

[IRobot1]

Description

When passing a simple 2 point line shape to SVGLoader pointToStroke, when linecap is set to square, the resulting geometry is incorrect.

It works correctly when linecap is either butt or round.

Reproduction steps

create a 2 point line shape
getStrokeStyle passing linecap set to 'square'
pass resulting shape and stroke style to pointsToStroke

Code

const shape = new Shape();
  shape.moveTo(-12, 0);
  shape.lineTo(12, 0);

  const style = SVGLoader.getStrokeStyle(
    2,
    "white",
    undefined,
    "square",
    undefined
  );

  const geometry = SVGLoader.pointsToStroke(shape.getPoints(), style);
  const material = new MeshBasicMaterial({ side: DoubleSide });
  const rect = new Mesh(geometry, material);
  scene.add(rect);

Live example

https://codesandbox.io/s/three-stroke-square-test-3yn756

Screenshots

Version

156.1

Device

Desktop

Browser

Edge

OS

Windows

[WestLangley]

FWIW, it works if you add an interleaving point.

const shape = new Shape();
  shape.moveTo( - 12, 0 );
  shape.lineTo( 0, 0 );
  shape.lineTo( 12, 0 );

[IRobot1]

When I rotate the scene (using orbit), the missing triangle is facing backwards. So likely the normal is just wrong or not being calculated.