Based on the discussion, plus some extra off-list discussion with Greg,
I've made the following changes:
* The `log-error', etc. forms still treat a single subexpression as a
literal string for the log message, but now they treat multiple
subexpressions as arguments to `format'.
This change balances backward compatibility, convenience, and
interaction with the new `racket/format' library (which I'll post
about on the dev list).
* Add `define-logger', where
(define-logger zoo)
binds
log-zoo-error
log-zoo-warning
...
that write to a logger that is created a child of `(current-logger)'
with the name 'zoo.
Unlike what I suggested before, the `define-logger' form doesn't
create a parameter and it doesn't inspect environment variables.
Those ideas were on the wrong track --- trying to filter at the
producer side, instead of the consumer side of logging.
* Changed `make-log-receiver' to accept a sequence of level symbols
and name symbols. For example,
(make-log-receiver logger 'debug 'GC 'error)
receives 'debug level events from children of `logger' that are
named 'GC, and it receives 'error events from all other loggers
under `logger'.
The logger name in a receiver affects `log-level?' queries in the
way that you'd expect, which avoids unnecessary work on the producer
side while keeping consumers in control.
* Changed -W, -L, PLTSTDERR, and PLTSYSLOG to allow specifications
like "debug@GC error", which is analogous to the `make-log-receiver'
call above. That is, a level can be suffixed with "@" and a logger
name to restrict the level specification to apply to a logger name.
Note that you can use
"debug none@optimizer"
to see all debug messages except those from 'optimizer, since a
level without a name applies only to loggers that are not otherwise
mentioned.
This change is based on Neil's suggestion, but with a syntax that I
find more suggestive and more in parallel to `make-log-receiver'.
* Changed the GC to log messages to a 'GC logger, the optimizer to log
to an 'optimizer logger, and the futures subsystem to log to a
'future logger.
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