Make primary writers public? about flexi_logger

[emabee]

In branch issue-47 I added a builder option 'Logger::duplicate_to_stdout()'.

With this, you could use

// Only log to stderr
        .log_target(LogTarget::StdErr)

// Log to stderr, and duplicate >= INFO to stdout
        .log_target(LogTarget::DevNull)  // only pretends to log
        .duplicate_to_stderr(Duplicate::All)
        .duplicate_to_stdout(Duplicate::Info)

// Log to file, duplicate ALL to stderr, nothing to stdout
        .log_target(LogTarget::File) 
        .duplicate_to_stderr(Duplicate::All)

// Log to file, duplicate to stderr, and duplicate >= INFO to stdout
        .log_target(LogTarget::File) 
        .duplicate_to_stderr(Duplicate::All)
        .duplicate_to_stdout(Duplicate::Info)

What do you think?

[pscott]

To make sure we avoid the XY problem, I'm trying to build a logger that works like this:

let log_file: Option<PathBuf>; // path to directory
let stderr_isatty = atty::is(atty::Stream::Stderr); // whether stderr is attached to a terminal or not
match (log_file, isatty) {
  (None, true) => , // Only log to stderr
  (None, false) => , // Log to stderr, and duplicate >= INFO to stdout
  (Some(dir), true) => ,// Log to file, duplicate ALL to stderr, nothing to stdout
  (Some(dir), false) => , // Log to file, duplicate to stderr, and duplicate >= INFO to stdout
}

edit: just noticed that duplication does not occur if log_target is Stderr or Stdout ^^'

[pscott]

Yup sounds good!
I would never have thought about using LogTarget::DevNull to "pretend" to log in order to be able to duplicate. It might be worth mentioning it in the docs somewhere (my two cents! :)).

Thank you so much for your help!

[emabee]

Implemented with version 0.15.5.

[pscott]

@emabee Getting back to this issue, I think I'm missing something like format_for_stdout() to be able to log with colors to stdout, while keeping LogTarget::Stderr and LogTarget::File without colors. Should I try submitting a PR for this one?