Warning / logging system?

[Fil]

In some cases we'd want Plot to warn the user about some kind of misconfiguration or unfit data that causes issues.

• data points mapped to nothing (Communicate information about filtered data points #493)
• negative data on a positive log scale (Instead of filtering oppositely-signed values for log scales, require an explicit sign #534)
• too many ordinal values (Hide tick labels when an ordinal x or y has a high-cardinality domain. #74)
• cycling the ordinal color scale because we have more categories than colors
• infinite values (ignore infinite values when setting a scale domain? #528)
• on-the-fly data coercion (coerce to the scale’s type #532)
• (more to add)

This meta-issue tries to capture all the cases when we'd want such a logging/warning system, and discussions on how they could be rendered.

A design issue is to know when it would be appropriate to display this — with a distinction between the case in which the user is actively coding (data exploration, development), vs. when the user passively consumes a chart, and the developer might want the chart to be more robust to errors.

[mbostock]

I think we should also consider throwing errors that prevent the chart from rendering, forcing the user to clarify something, in cases where we do not think we can make a reasonable interpretation of the chart specification.