Could color be disabled?

[nbigaouette]

I really like the new format, including the color!

Unfortunately when the log output is piped and stored elsewhere (for example in AWS CloudWatch) I see all the control characters which makes reading the log actually harder.

Could the color be disabled with a feature flag?

[KodrAus]

Hi @nbigaouette. I think this is a reasonable thing for us to do. Rather than a feature flag I think an environment variable might be a better fit here (since it's the environment that determines whether or not colours are going to be useful).

Like other env_logger settings, we can pick up this environment variable in the default builder, or let you read it yourself when configuring a logger. Maybe we can call the default environment variable RUST_LOG_STYLE. A value of 0 means no colour or styling. If there is no value, or it's not 0, then we write colour and style. This is the opposite behaviour to the RUST_BACKTRACE environment variable.

What do you think?

[nbigaouette]

An environment variable makes absolute sense, specially for env_logger... ;)

The advantage of a feature flag would be to prevent having to pull some dependencies, which might speed up CI runs.

I feel like RUST_LOG_STYLE sounds more a way to control the style, not an on-off flag. But that's still what the 0 or 1 value mean, it applies a style to the logging (or not). There's not much else that it can do; either there is style, or there isn't.

In any way, the variable you suggested would definitely fit my use case! Thanks a lot! 👍

[kpcyrd]

I'd suggest to align this with cargo and others, so you would have never, always and auto, where auto means it tests if it's writing to a tty and disables colors if it isn't. This is usually good enough. If you run ./app on your terminal you have colors, if you run ./app > log 2>&1 you don't. :)

[KodrAus]

Ah thanks @kpcyrd! I hadn't realised cargo had values for adjusting style output already. I was aligning this with RUST_BACKTRACE, but aligning with --color makes much more sense.