Logger implementation

I’m opening this issue to start discussion on vision for logging module.

Coming from Python world and being familiar with its library, my intent for Deno logging was to emulate Python’s approach.

Its mechanism is based on:

• loggers - object to call to log something obviously
• LogRecord - contains timestamps and metadata about message logged by logger
• handlers - also known as transports. One logger may utilize multiple `handlers. Eg. console handler that print output to console, file handler that streams logs to file on disk.
• filters - predicates that interact with LogRecords, allowing for very granular control. Both loggers and handlers can have filters
• formatters - a function that given LogRecord instance returns output string

Loggers are accessed using getLogger function, so wherever in code you do const logger = logging.getLogger('myLogger'); you get the same instance.

This page gives a nice overview how to use it in action.

One of more popular node’s logging libraries winston takes not so different approach.

I’m really interested what community expects.

[ry]

My initial idea was to leverage Error.stack but I’m concerned with performance, throwing error at each logged message can’t be a good idea.

Hm… It’s possible we could provide __LINE__ as a preprocessed symbol in deno. For the filename we could use import.meta once https://github.com/denoland/deno/issues/975 lands.

[bartlomieju]

I reckon log implementation is good enough now we can close this.