Format::without_time makes it hard to enable/disable timestamps at runtime

[azerupi]

Bug Report

Version

tracing = "0.1.41"
tracing-subscriber = "0.3.19"

But this is also present in master.

Crates

• tracing-subscriber

Description

I'm trying to display the timestamp depending on the log level but the API makes this harder than expected.

In the Format methods there are a bunch of methods of the form with_xxx(self, bool). But the method that allows enabling or disabling the timestamps breaks this pattern by being called without_time(self) and not accepting a boolean.

Additionally, calling without_time changes the type, so its not as simple as just breaking up the builder to add an if.

https://docs.rs/tracing-subscriber/latest/tracing_subscriber/fmt/format/struct.Format.html#method.without_time

Desired:

let format = fmt::format()
    .with_level(true)
    .with_target(show_log_details)
    .with_thread_ids(false)
    .with_thread_names(false)
    .with_timestamp(show_log_details)
    .compact();

tracing_subscriber::fmt()
    .event_format(format)
    .with_max_level(verbosity)
    .init();

Current solution:

let show_log_details = matches!(verbosity, Verbosity::Debug | Verbosity::Trace);

let format = fmt::format()
    .with_level(true)
    .with_target(show_log_details)
    .with_thread_ids(false)
    .with_thread_names(false)
    .compact();

if show_log_details {
    tracing_subscriber::fmt()
        .event_format(format)
        .with_max_level(verbosity)
        .init();
} else {
    let format = format.without_time();

    tracing_subscriber::fmt()
        .event_format(format)
        .with_max_level(verbosity)
        .init();
}

I saw that there was an open PR to fix this: #2084 but it hasn't received any updates since 2022.