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Re: [MirageOS-devel] Logs

On 17 October 2015 at 15:04, Daniel BÃnzli <daniel.buenzli@xxxxxxxxxxxx> wrote:
> Le samedi, 17 octobre 2015 Ã 12:49, Thomas Leonard a Ãcrit :
>> (but OCaml libraries don't generally do any logging at all, so it's not a 
>> huge issue).
> And this tradition should continue as much as possible.
>> Makes sense (I'd expect it to go between warning and info - I can
>> imagine wanting to suppress progress without suppressing errors).
> It doesn't really match what I expect from this level which I really see like 
> the stdout of you program. So I'd like to be able to redirect the output of 
> the program without e.g. getting errors or warnings in the output.

Thinking on about this, I don't think it makes sense to have a log
level that goes to stdout by default. All libraries can log, but they
shouldn't be able to write to the program's output. e.g. consider:

  curl URL > file.html

If some library wants to make sure the user sees a message (Log.show
"Connected!" or something), that should go to stderr, where the use
will see it, not to stdout where the downloaded HTML is being written.

> For me it is also distinct from the info level which I'd use to inform a bit 
> more about what is happening internally in the program.

Yes, a log level for messages that are more important than info
(should be shown by default even in interactive applications) but do
not indicate problems sounds reasonable. "Log.notice" still sounds
right to me for this.

> Of course you could use a special log source for that but then you'd need to 
> devise a special log reporter for that, so I prefer if all the reporters have 
> to acknowledge the existence of that level and its supposed semantics.

I think anything that writes to stdout should need explicit
configuration from the application.

> So for now I have kept that as the lowest level and renamed it to `App` 
> rather than `Show`. I may still kill the concept though.
> Daniel

Dr Thomas Leonard        http://roscidus.com/blog/
GPG: DA98 25AE CAD0 8975 7CDA  BD8E 0713 3F96 CA74 D8BA

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