Helpers for error messages

[hadley]

(Meta issue, will edit as I come across more small helpers):

dir_copy(c("foo", NA_character_, "bar", NA_character_), "blah")
#> Error: `path` must not have missing values
#> NAs found at 1,000,000 locations: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...

• Number formatting (e.g. set big mark)
• Commas + truncation
• Standard wrappers for argument names, paths, expressions

[jimhester]

r-lib/fs@df2252a is the code I am using in fs for this

[gaborcsardi]

Maybe #37 is relevant here, the inline markup part.

[gaborcsardi]

Should this be in cli at all? Shall we use glue for the formatting? I think we already have some of these functions in other packages, no? Where?

@hadley @jimhester

[hadley]

I think some of probably belong in cli — e.g. cli should provide standard colours + text formatting for when we put an argument name or a string in a message. But maybe you're thinking that should live in a higher level package where those settings can be controlled with a theme?

[gaborcsardi]

A common theme would be definitely nice. Theming is now in the cliapp package, but that's a bit too heavy as it is now, for a low-level infrastructure package, it needs xml2, selectr, progress. It is possible that we don't need hierarchical theming for CLI apps. OTOH it is really nice to have it. We can work on thinning its dependencies.

[gaborcsardi]

OK, this will be proposed for after the coming 1.1.0 version, and I'll collect some use cases and mock up some API.