There should be no source color highlighting if the label points to the whole line, or if the label is multiline

[RDambrosio016]

Codespan currently highlights in red whatever the primary label is pointing to in the source, while this looks great for errors inside of source code lines, it looks really ugly if the label points to the whole line. It ruins the point of highlighting, you can clearly see what the label is pointing at, a line of all red just looks like it does not belong there. In the case of multiline labels, usually they are used to point to blocks of source code, but this means if you highlight everything inside of them you end up with a giant blob of RED which just looks like it does not belong and it ruins the cleanliness of the diagnostic.

Labels should highlight their source code only if the label points to a subsection of the source code line, and should be fully disabled for multiline labels.

[brendanzab]

Yeah, this was definitely one of my original concerns about adding source highlighting - see #206 (comment) - maybe special casing full lines and multiline might be ok?

cc. @jonathandturner @dtolnay

[Johann150]

@RDambrosio016 What would you consider to be the "whole line"? All text (optionally without the leading whitespace). What about trailing whitespace?

[RDambrosio016]

@Johann150 the whole line is the line of source code will All leading and trailing whitespace removed, as this isnt really viewable so there is no point in counting it in

[RDambrosio016]

Note that this also means that no highlighting should be done if the label goes over the actual source and into trailing or leading whitespace

[brendanzab]

One thing I'm pondering is whether it would be better to do this as a simpler configuration option. Like, personally I'm not the biggest fan of the source highlighting, but perhaps we could add in a boolean flag to enable it? I guess I'm just worried about adding complicated heuristics around this, and how good it will actually look in practice, or whether it will end up confusing people.

[Johann150]

Do you mean that this option should turn off all highlighting and just rely on the underlines?

[brendanzab]

Yeah - thinking of how rustc normally renders errors. Maybe an option like highlight_source or something 🤔

[Johann150]

I think that is not related to this issue