DeftLog

A factory for building swift-log Loggers while adding centralized control over logLevel. Can be used by libraries to surface their logging options to applications.

Need

DeftLog provides a way for a program to configure log levels for all DeftLog-enabled libraries at logger label granularity.

In swift-log, the decision about whether to log a message is made by each logger; the Logger's extension checks the message against each instance's logLevel and does not forward the message to the log hander if the message does not reach the configured threshold. LogLevel is intended to be part of the Logger state; implementors of alternate Loggers are discouraged from centrally adjusting logLevel.

swift-log doesn't suggest any particular pattern for setting logLevel. For implementors of package libraries who want to allow library consumers to adjust logLevel, they are left on their own to plumb the setting of logLevel into private Loggers. This library offers a pattern where the main runtime can describe desired log levels early in execution, and then the library's Logger factory will offer Loggers to the implementor that default to the logLevel specified at the executable level.

Usage

Configuring

Near the start of the program, before libraries start requesting their loggers, set the configuration:

DeftLog.settings = [
    ("com.didactek.deft-log", .critical),
    ("com.didactek.deft-mcp2221.usb", .trace),
    ("com.didactek.deft-mcp2221", .debug),
]

Obtaining Loggers

// Will be .debug using above settings
let logger = DeftLog.logger(label: "com.didactek.deft-mcp2221.hidapi")

The settings are searched from start to end, looking for the first match against a label prefix. If no match is found, the default logLevel (as set by the initializer) is unchanged.

DeftLog.logger(label:) returns a Logger created from swift-log. It will be connected to the bootstrapped log handler backend in the usual manner.

DocC

Includes documentation.