Names of missing required arguments are always colorized

[dotdash]

Affected Version of clap

2.19.2

Expected Behavior Summary

Coloring is only applied when output is sent to a terminal.

Actual Behavior Summary

The name of the missing required argument is always colorized, giving messed up output e.g. capturing output into vim's quickfix buffer.

|| [cargo run --bin render]                                                                                                                  
|| unused variable: `matches`, #[warn(unused_variables)] on by default                                                                       
||    |                                                                                                                                      
|| 33 |     let matches = App::new("My  app")                                                                                                
||    |         ^^^^^^^                                                                                                                      
||-                                                                                                                                          
||      Running `target/debug/render`                                                                                                        
|| The following required arguments were not provided:                                                                                       
||     ^[[1;31m<CONFIG>^[[0m                                                                                                                 
||-                                                                                                                                          
|| USAGE:                                                                                                                                    
||     render <CONFIG> <WIDTH> <HEIGHT>                                                                                                      
||-                                                                                                                                          
|| For more information try --help                                                                                                           
|| [Finished in 1 seconds with code 1]              

[kbknapp]

Is this with using AppSettings::ColorNever?

[dotdash]

It's not, but even with it, that one thing is still colored.

[dotdash]

OK, this is because the closure in validate_required directly uses Format::Error instead of the Colorizer and thus unconditonally emits ANSI color codes. The quick fix would be to create a Colorizer there, and using its error() method instead. Is that an acceptable approach (I'm not familiar with the code base)?

[kbknapp]

Great catch! Yeah that would be an acceptable fix. I'm on mobile right now, so if you'd like to do the PR feel free 😉