Allow Jekyll's logger to be set to any Logger compatible instance

* Stevenson now inherits from Logger and extends some methods to use $stderr
for log messages greater than info level.
* LogWriter provides an interface between Jekyll and Logger to maintain API.

lib/jekyll.rb

@@ -31,6 +31,7 @@ require 'toml'
 # internal requires
 require 'jekyll/version'
 require 'jekyll/utils'
+require 'jekyll/log_writer'
 require 'jekyll/stevenson'
 require 'jekyll/deprecator'
 require 'jekyll/configuration'
@@ -115,7 +116,11 @@ module Jekyll
   end
 
   def self.logger
-    @logger ||= Stevenson.new
+    @logger ||= LogWriter.new(Stevenson.new)
+  end
+
+  def self.logger=(writer)
+    @logger = LogWriter.new(writer)
   end
 
   # Public: File system root

lib/jekyll/log_writer.rb

@@ -0,0 +1,103 @@
+require 'logger'
+module Jekyll
+  class LogWriter
+    attr_reader :writer
+
+    LOG_LEVELS = {
+      debug: 0,
+      info:  1,
+      warn:  2,
+      error: 3
+    }
+
+    # Public: Create a new instance of Jekyll's log writer
+    #
+    # writer - Logger compatible instance
+    # log_level - (optional, symbol) the log level
+    #
+    # Returns nothing
+    def initialize(writer, level = :info)
+      @writer = writer
+      self.log_level = level
+    end
+
+    # Public: Set the log level on the writer
+    #
+    # level - (symbol) the log level
+    #
+    # Returns nothing
+    def log_level=(level)
+      writer.level = LOG_LEVELS.fetch(level)
+    end
+
+    # Public: Print a jekyll debug message
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail
+    #
+    # Returns nothing
+    def debug(topic, message = nil)
+      writer.debug(message(topic, message))
+    end
+
+    # Public: Print a jekyll message
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail
+    #
+    # Returns nothing
+    def info(topic, message = nil)
+      writer.info(message(topic, message))
+    end
+
+    # Public: Print a jekyll message
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail
+    #
+    # Returns nothing
+    def warn(topic, message = nil)
+      writer.warn(message(topic, message).yellow)
+    end
+
+    # Public: Print a jekyll error message
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail
+    #
+    # Returns nothing
+    def error(topic, message = nil)
+      writer.error(message(topic, message).red)
+    end
+
+    # Public: Print a Jekyll error message and immediately abort the process
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail (can be omitted)
+    #
+    # Returns nothing
+    def abort_with(topic, message = nil)
+      error(topic, message)
+      abort
+    end
+
+    # Public: Build a Jekyll topic method
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail
+    #
+    # Returns the formatted message
+    def message(topic, message)
+      formatted_topic(topic) + message.to_s.gsub(/\s+/, ' ')
+    end
+
+    # Public: Format the topic
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    #
+    # Returns the formatted topic statement
+    def formatted_topic(topic)
+      "#{topic} ".rjust(20)
+    end
+  end
+end

lib/jekyll/stevenson.rb

@@ -1,102 +1,49 @@
+require 'logger'
 module Jekyll
-  class Stevenson
-    attr_accessor :log_level
-
-    LOG_LEVELS = {
-      debug: 0,
-      info:  1,
-      warn:  2,
-      error: 3
-    }
-
-    # Public: Create a new instance of Stevenson, Jekyll's logger
-    #
-    # level - (optional, symbol) the log level
-    #
-    # Returns nothing
-    def initialize(level = :info)
-      @log_level = level
+  class Stevenson < ::Logger
+    def initialize
+      @progname = nil
+      @level = DEBUG
+      @default_formatter = Formatter.new
+      @logdev = $stdout
+      @formatter = proc do |severity, datetime, progname, msg|
+        "#{msg}"
+      end
     end
 
-    # Public: Print a jekyll debug message to stdout
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    # message - the message detail
-    #
-    # Returns nothing
-    def debug(topic, message = nil)
-      $stdout.puts(message(topic, message)) if should_log(:debug)
+    def add(severity, message = nil, progname = nil, &block)
+      severity ||= UNKNOWN
+      @logdev = set_logdevice(severity)
+
+      if @logdev.nil? or severity < @level
+        return true
+      end
+      progname ||= @progname
+      if message.nil?
+        if block_given?
+          message = yield
+        else
+          message = progname
+          progname = @progname
+        end
+      end
+      @logdev.puts(
+        format_message(format_severity(severity), Time.now, progname, message))
+      true
     end
 
-    # Public: Print a jekyll message to stdout
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    # message - the message detail
-    #
-    # Returns nothing
-    def info(topic, message = nil)
-      $stdout.puts(message(topic, message)) if should_log(:info)
+    def close
+      # No LogDevice in use
     end
 
-    # Public: Print a jekyll message to stderr
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    # message - the message detail
-    #
-    # Returns nothing
-    def warn(topic, message = nil)
-      $stderr.puts(message(topic, message).yellow) if should_log(:warn)
-    end
+    private
 
-    # Public: Print a jekyll error message to stderr
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    # message - the message detail
-    #
-    # Returns nothing
-    def error(topic, message = nil)
-      $stderr.puts(message(topic, message).red) if should_log(:error)
-    end
-
-    # Public: Print a Jekyll error message to stderr and immediately abort the process
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    # message - the message detail (can be omitted)
-    #
-    # Returns nothing
-    def abort_with(topic, message = nil)
-      error(topic, message)
-      abort
-    end
-
-    # Public: Build a Jekyll topic method
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    # message - the message detail
-    #
-    # Returns the formatted message
-    def message(topic, message)
-      formatted_topic(topic) + message.to_s.gsub(/\s+/, ' ')
-    end
-
-    # Public: Format the topic
-    #
-    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
-    #
-    # Returns the formatted topic statement
-    def formatted_topic(topic)
-      "#{topic} ".rjust(20)
-    end
-
-    # Public: Determine whether the current log level warrants logging at the
-    #         proposed level.
-    #
-    # level_of_message - the log level of the message (symbol)
-    #
-    # Returns true if the log level of the message is greater than or equal to
-    #   this logger's log level.
-    def should_log(level_of_message)
-      LOG_LEVELS.fetch(log_level) <= LOG_LEVELS.fetch(level_of_message)
+    def set_logdevice(severity)
+      if severity > INFO
+        $stderr
+      else
+        $stdout
+      end
     end
   end
 end