Unexpected arcs when corner radius is nonzero

[tkonopka]

Hello and thank you for providing this library.

I traced some unexpected behavior in another library (reported here) to arcs in d3-shape. It only affects extremely short arcs when cornerRadius is nonzero.

In this example, the first two rows show expected behavior. In the third row, the angles are very similar, and the generated arcs are invisible (as expected). The angles are even more similar in the fourth row, but one of the arcs flips direction (unexpected).

This is not too much bother because it is straightforward to filter out such arcs before rendering, but mentioning it here as a curiosity.

https://codesandbox.io/s/dry-pine-7m88p9?file=/src/App.js

[mbostock]

Reproduction https://observablehq.com/d/41da02e4ede0cabc