Adding log level methods when using Logger class

lib/winston/create-logger.js

@@ -7,14 +7,8 @@
 
 'use strict';
 
-const { LEVEL } = require('triple-beam');
 const config = require('./config');
 const Logger = require('./logger');
-const debug = require('@dabh/diagnostics')('winston:create-logger');
-
-function isLevelEnabledFunctionName(level) {
-  return 'is' + level.charAt(0).toUpperCase() + level.slice(1) + 'Enabled';
-}
 
 /**
  * Create a new instance of a winston Logger. Creates a new
@@ -47,58 +41,7 @@ module.exports = function (opts = {}) {
 
   const logger = new DerivedLogger(opts);
 
-  //
-  // Create the log level methods for the derived logger.
-  //
-  Object.keys(opts.levels).forEach(function (level) {
-    debug('Define prototype method for "%s"', level);
-    if (level === 'log') {
-      // eslint-disable-next-line no-console
-      console.warn('Level "log" not defined: conflicts with the method "log". Use a different level name.');
-      return;
-    }
-
-    //
-    // Define prototype methods for each log level e.g.:
-    // logger.log('info', msg) implies these methods are defined:
-    // - logger.info(msg)
-    // - logger.isInfoEnabled()
-    //
-    // Remark: to support logger.child this **MUST** be a function
-    // so it'll always be called on the instance instead of a fixed
-    // place in the prototype chain.
-    //
-    DerivedLogger.prototype[level] = function (...args) {
-      // Prefer any instance scope, but default to "root" logger
-      const self = this || logger;
-
-      // Optimize the hot-path which is the single object.
-      if (args.length === 1) {
-        const [msg] = args;
-        const info = msg && msg.message && msg || { message: msg };
-        info.level = info[LEVEL] = level;
-        self._addDefaultMeta(info);
-        self.write(info);
-        return (this || logger);
-      }
-
-      // When provided nothing assume the empty string
-      if (args.length === 0) {
-        self.log(level, '');
-        return self;
-      }
-
-      // Otherwise build argument list which could potentially conform to
-      // either:
-      // . v3 API: log(obj)
-      // 2. v1/v2 API: log(level, msg, ... [string interpolate], [{metadata}], [callback])
-      return self.log(level, ...args);
-    };
-
-    DerivedLogger.prototype[isLevelEnabledFunctionName(level)] = function () {
-      return (this || logger).isLevelEnabled(level);
-    };
-  });
+  logger.createLogLevelMethods(logger, opts.levels);
 
   return logger;
 };

lib/winston/logger.js

@@ -17,6 +17,7 @@ const LegacyTransportStream = require('winston-transport/legacy');
 const Profiler = require('./profiler');
 const { warn } = require('./common');
 const config = require('./config');
+const debug = require('@dabh/diagnostics')('winston:create-logger');
 
 /**
  * Captures the number of format (i.e. %s strings) in a given string.
@@ -149,6 +150,57 @@ class Logger extends Transform {
     }
   }
 
+  //
+  // Create the log level methods for the derived logger.
+  //
+  createLogLevelMethods(logger, levels) {
+    Object.keys(levels).forEach(function (level) {
+      debug('Define prototype method for "%s"', level);
+      if (level === 'log') {
+        // eslint-disable-next-line no-console
+        console.warn('Level "log" not defined: conflicts with the method "log". Use a different level name.');
+        return;
+      }
+      //
+      // Define prototype methods for each log level e.g.:
+      // logger.log('info', msg) implies these methods are defined:
+      // - logger.info(msg)
+      // - logger.isInfoEnabled()
+      //
+      // Remark: to support logger.child this **MUST** be a function
+      // so it'll always be called on the instance instead of a fixed
+      // place in the prototype chain.
+      //
+      Logger.prototype[level] = function (...args) {
+        // Prefer any instance scope, but default to "root" logger
+        const self = this || logger;
+        // Optimize the hot-path which is the single object.
+        if (args.length === 1) {
+          const [msg] = args;
+          const info = msg && msg.message && msg || { message: msg };
+          info.level = info[LEVEL] = level;
+          self._addDefaultMeta(info);
+          self.write(info);
+          return (this || logger);
+        }
+        // When provided nothing assume the empty string
+        if (args.length === 0) {
+          self.log(level, '');
+          return self;
+        }
+        // Otherwise build argument list which could potentially conform to
+        // either:
+        // . v3 API: log(obj)
+        // 2. v1/v2 API: log(level, msg, ... [string interpolate], [{metadata}], [callback])
+        return self.log(level, ...args);
+      };
+      const isLevelEnabledFunctionName = 'is' + level.charAt(0).toUpperCase() + level.slice(1) + 'Enabled';
+      Logger.prototype[isLevelEnabledFunctionName] = function () {
+        return (this || logger).isLevelEnabled(level);
+      };
+    });
+  }
+
   isLevelEnabled(level) {
     const givenLevelValue = getLevelValue(this.levels, level);
     if (givenLevelValue === null) {

test/unit/winston/logger.test.js

@@ -201,6 +201,32 @@ describe('Logger Instance', function () {
   });
 
   describe('Log Levels', function () {
+    it('create log level methods using Logger class', function (done) {
+      stdMocks.use();
+      const logger = new winston.Logger({
+        level: 'info',
+        transports: [new winston.transports.Console()],
+        format: winston.format.combine(winston.format.splat(), winston.format.colorize({ all: true }), winston.format.simple())
+      })
+      logger.error('test');
+      logger.warn('test');
+      logger.info('test');
+      logger.verbose('test');
+      logger.debug('test');
+      logger.silly('test');
+
+      stdMocks.restore();
+
+      assume(logger.error).is.a('function');
+      assume(logger.warn).is.a('function');
+      assume(logger.info).is.a('function');
+      assume(logger.verbose).is.a('function');
+      assume(logger.debug).is.a('function');
+      assume(logger.silly).is.a('function');
+
+      done();
+    });
+
     it('report unknown levels', function (done) {
       stdMocks.use();
       let logger = helpers.createLogger(function (info) {