Add reraise_write_errors keyword argument to Logger and LogDevice

This allows the user to specify exception classes to treat as regular
exceptions instead of being swallowed.  Among other things, it is
useful for having Logger work with Timeout when having Timeout raise
a specific subclass.

Fixes Ruby Bug 9115.

lib/logger.rb

@@ -370,14 +370,19 @@ def fatal!; self.level = FATAL; end
   # +shift_period_suffix+::
   #   The log file suffix format for +daily+, +weekly+ or +monthly+ rotation.
   #   Default is '%Y%m%d'.
+  # +reraise_write_errors+::
+  #   An array of exception classes, which will be reraised if there is an
+  #   error when writing to the log device. The default is to swallow all
+  #   exceptions raised.
   #
   # === Description
   #
   # Create an instance.
   #
   def initialize(logdev, shift_age = 0, shift_size = 1048576, level: DEBUG,
                  progname: nil, formatter: nil, datetime_format: nil,
-                 binmode: false, shift_period_suffix: '%Y%m%d')
+                 binmode: false, shift_period_suffix: '%Y%m%d',
+                 reraise_write_errors: [])
     self.level = level
     self.progname = progname
     @default_formatter = Formatter.new
@@ -388,7 +393,8 @@ def initialize(logdev, shift_age = 0, shift_size = 1048576, level: DEBUG,
       @logdev = LogDevice.new(logdev, shift_age: shift_age,
         shift_size: shift_size,
         shift_period_suffix: shift_period_suffix,
-        binmode: binmode)
+        binmode: binmode,
+        reraise_write_errors: reraise_write_errors)
     end
   end
 

lib/logger/log_device.rb

@@ -11,9 +11,10 @@ class LogDevice
     attr_reader :filename
     include MonitorMixin
 
-    def initialize(log = nil, shift_age: nil, shift_size: nil, shift_period_suffix: nil, binmode: false)
+    def initialize(log = nil, shift_age: nil, shift_size: nil, shift_period_suffix: nil, binmode: false, reraise_write_errors: [])
       @dev = @filename = @shift_age = @shift_size = @shift_period_suffix = nil
       @binmode = binmode
+      @reraise_write_errors = reraise_write_errors
       mon_initialize
       set_dev(log)
       if @filename
@@ -34,16 +35,22 @@ def write(message)
           if @shift_age and @dev.respond_to?(:stat)
             begin
               check_shift_log
+            rescue *@reraise_write_errors
+              raise
             rescue
               warn("log shifting failed. #{$!}")
             end
           end
           begin
             @dev.write(message)
+          rescue *@reraise_write_errors
+            raise
           rescue
             warn("log writing failed. #{$!}")
           end
         end
+      rescue *@reraise_write_errors
+        raise
       rescue Exception => ignored
         warn("log writing failed. #{ignored}")
       end

test/logger/test_logger.rb

@@ -113,6 +113,15 @@ def test_string_level
     assert_raise(ArgumentError) { @logger.level = 'something_wrong' }
   end
 
+  def test_reraise_write_errors
+    c = Object.new
+    e = Class.new(StandardError)
+    c.define_singleton_method(:write){|*| raise e}
+    c.define_singleton_method(:close){}
+    logger = Logger.new(c, :reraise_write_errors=>[e])
+    assert_raise(e) { logger.warn('foo') }
+  end
+
   def test_progname
     assert_nil(@logger.progname)
     @logger.progname = "name"