More convenience options for child logger filtering

Author: FoxxMD

README.md

@@ -205,6 +205,9 @@ nestedChild1.debug('I am nested one level');
 const nestedChild2 = childLogger(nestedChild1, ['Second', 'Third'], { level: 'silent' });
 nestedChild2.info('I do not log because of set level and not enabled by filter');
 
+// without LOG_FILTER_ENABLE from above set, the below logging would be silent
+// because they inherit the level from their parent
+
 const nestedChild3 = childLogger(nestedChild2, ['Fourth']);
 nestedChild3.info('I do log because of filter Third:Fourth');
 
@@ -215,6 +218,18 @@ const nestedChild5 = childLogger(nestedChild4, ['Bar']);
 nestedChild5.info('I do log because of filter Bar');
 ```
 
+The minimum level a child logger is "enabled" to is ENV `LOG_FILTER_ENABLE_LEVEL` or `trace`, by default. It can also be specified by passing `labelEnableLevel` to childLogger options.
+
+The minimum level a child logger is "disabled" to is ENV `LOG_FILTER_DISABLE_LEVEL` or `silent`, by default. It can also be specified by passing `labelDisableLevel` to childLogger options.
+
+There are also options for passing your own function to determine if a child logger should be enabled or disabled. See [`childLogger`](https://foxxmd.github.io/logging/functions/index.childLogger.html) docs for full a full reference.
+
+A caveat to be aware of: **enable/disable by filter is evaluated once, when `childLogger` is instantiated.** This means:
+
+* Only the labels added by `childLogger` insantiation are applicable. Labels added during logging, IE `logger.info({labels: ['Runtime']}, "a log")`, are not considered.
+* Labels that are functions are evaluated **once**, when `childLogger` is instantiated
+* Changing the `LOG_FILTER_*` envs after a childLogger is created will have no effect on it
+
 ### Serializing Objects and Errors
 
 Passing an object or array as the first argument to the logger will cause the object to be JSONified and pretty printed below the log message

src/loggers.ts

@@ -97,9 +97,9 @@ export const buildLogger = (defaultLevel: LogLevel, streams: LogLevelStreamEntry
 export const childLogger = (parent: Logger, labelsVal: any | any[] = [], context: object = {}, options: ChildLoggerOptions = {}): Logger => {
     const {
         labelEnable = labelsEnableFromEnvSingleton,
-        labelEnableLevel = parent.level,
+        labelEnableLevel = process.env.LOG_FILTER_ENABLE_LEVEL ?? 'trace',
         labelDisable = labelsDisableFromEnvSingleton,
-        labelDisableLevel = 'silent',
+        labelDisableLevel = process.env.LOG_FILTER_DISABLE_LEVEL ?? 'silent',
         ...rest
     } = options;