Make primary writers public?

[pscott]

I'm trying to log things to a file, stderr, and stdout at the same time.

To do that I must create a new writer for Stdout which I've done this way:

struct StdoutWriter {
    format: FormatFunction,
    log_level: log::LevelFilter
}

impl StdoutWriter {
    fn new(format: FormatFunction, log_level: LevelFilter) -> Self {
        StdoutWriter { format, log_level}
    }
}

impl LogWriter for StdoutWriter {
    #[inline]
    fn write(&self, now: &mut DeferredNow, record: &Record) -> std::io::Result<()> {
        (self.format)(&mut std::io::stdout(), now, record)
    }

    fn flush(&self) -> std::io::Result<()> {
        std::io::stdout().flush()
    }

    fn max_log_level(&self) -> log::LevelFilter {
        self.log_level
    }
}

However, I was wondering if flexi_logger couldn't expose the StdoutWriter that it already uses internally (as a Primary Writer), to make that easier.
Or maybe I'm missing something :)

Thanks!

[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 ^^'

[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]

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?