Mercator. Getting boundary values by longitude

[dowhileforeach]

I use d3-geo 3.1.0

Without rotation (everything works well)

const geoToProj = geoMercator().rotate([0, 0, 0]);

console.log('[-180,0] ->', geoToProj([-180,0]));
console.log('[180,0] ->', geoToProj([180,0]));

output:

[-180,0] -> [-0.5, 250]
[180,0] -> [960.5, 250]

it seems there are no problems here, the only thing is not clear why -0.5 and 960.5, and not 0 and 960...

Rotate, lambda -10 (unexpected behavior)

const geoToProj = geoMercator().rotate([-10, 0, 0]);

console.log('[-170,0] ->', geoToProj([-170,0]));
console.log('[190,0] ->', geoToProj([190,0]));

const roundD3Bound = (n) => n - 0.0000000000001;
console.log('[190 rounded,0] ->', geoToProj([roundD3Bound(190),0]));

output:

[-170,0] -> [-0.5, 250]
[190,0] -> [-0.49999999999994316, 250]
[190 rounded,0] -> [960.4999999999998, 250]

I rotated the projection to lambda -10 degrees.
Accordingly, I expect the longitude boundaries to be -170 and 190.
As a result, the geographic point [-170,0] on the projection [-0.5, 250]
matches the geographical point [190,0] on the projection [-0.49999999999994316, 250].

And only such a geographical point [189.9999999999999, 0] on the projection will be where it is expected [960.4999999999998, 250].

Check it. Stackblitz

Question

Is there a method to get the longitude boundary values for the projection?
That is, for example, for projection geoMercator().rotate([-10, 0, 0])
I call the method "give boundary values for longitude" and it returns to me left=-170, right=189.9999999999999?

[mbostock]

You can’t rely on [190,0] being distinct from [-170, 0]; they represent the same point on the sphere. Same with [-180, 0] and [180, 0]; it’s somewhat coincidental that it works in this case due to floating point. If you want to compute the bounds of something, use path.bounds, say with {type: "Sphere"} for the entire globe.

[dowhileforeach]

Mike, thank you for the hint about using path.bounds.
As a result, the boundary values of the mercator, expressed in geographical coordinates, now I get this way:

function mercatorGeoBounds(lambda: number) {
  const geoToProj = geoMercator().rotate([lambda, 0, 0]);
  const projToGeo = geoToProj.invert;
  const [leftTopBoundPointOnProj, rightBottomBoundPointOnProj] = geoPath().projection(geoToProj).bounds({type: 'Sphere'});
  const leftTopBoundPoint = projToGeo(leftTopBoundPointOnProj);
  const rightBottomBoundPoint = projToGeo(rightBottomBoundPointOnProj);

  const [lonLeft, latTop] = leftTopBoundPoint;
  return {
    lonLeft,
    lonRight: (lonLeft + 360) - 0.000000000001,
    latTop,
    latBottom: rightBottomBoundPoint[1],
  };
}