Legend not showing when values are var(...)

[vincent-octo]

Hello,

When using color: {legend: true} and values are "var(--something)" then the legend does not appear.
Additionally, I could not see any warning or error message that could help in understanding why the legend doesn't show.

Here is an notebook that reproduces the bug: https://observablehq.com/d/fbd79535abd8788a
Changing fill: "test" with fill: "sex" will display the legend again, so I am assuming that the "var(...)" content of test is to blame here.

[Fil]

When the values are passed as literal colors, there is no color scale, and as a consequence no legend.

to fix, you could try using "sex" again, with something like this for the color option:

color: {
  legend: true,
  domain: ["FEMALE", "MALE", null],
  range: ["var(--female)", "var(--male)", "var(--null)"]
},

[vincent-octo]

Thanks! That does indeed fix it. :)

I was a little lost as to why the bug occured at first, and a hint from an error/warning message would have probably saved some time. Could adding such a message be considered?

[Fil]

I've added this to the list in #755