zeroline doesn't display when showline=true

[cldougl]

Using rangemode: 'tozero' and zeroline: true to always display zero line doesn't display zero line when showline=true is added to the axis.
Example: https://codepen.io/plotly/pen/WvPgPP?editors=1010

[etpinard]

Looks like that's on-purpose from the !ax.showline part of

plotly.js/src/plots/cartesian/axes.js

Lines 2173 to 2175 in 41d870b

	showZl = (rng[0] * rng[1] <= 0) && ax.zeroline &&
	(ax.type === 'linear' || ax.type === '-') && gridvals.length &&
	(hasBarsOrFill || clipEnds({x: 0}) || !ax.showline);

[etpinard]

.... not sure why though.

[alexcjohnson]

I suspect that was intended to be the opposite axis showline - so we don't show two lines nearly on top of each other. Notice that that's the effect it has - if you move zero just a little away from the end of the axis, the zero line will show up again.

Nice catch @cldougl

[yifan-yang]

@cldougl when do you think this can be deployed?

[cldougl]

@yifan-yang the activity will be logged in this issue.

[yifan-yang]

@cldougl thanks, what would be the usual ETA for such case?