Fix setting a more verbose thread-local log level

We prepend a check against the thread-local level to Logger#add, but because it proceeds to check against the thread-global level, only setting a quieter thread-local level works. The quietest of the two wins. Fix by reimplementing #add entirely.

It's unfortunate to have to do this, but I've already patched upstream Logger to prefer the level instance method over the @level instance variable, so we'll be able to avoid touching #add at all in the future. See https://github.com/ruby/logger/pull/41.

activesupport/lib/active_support/logger_thread_safe_level.rb

@@ -48,9 +48,25 @@ module ActiveSupport
       local_level || super
     end
 
+    # Redefined to check severity against #level, and thus the thread-local level, rather than +@level+.
+    # FIXME: Remove when the minimum Ruby version supports overriding Logger#level.
     def add(severity, message = nil, progname = nil, &block) # :nodoc:
-      return true if @logdev.nil? || (severity || UNKNOWN) < level
-      super
+      severity ||= UNKNOWN
+      progname ||= @progname
+
+      return true if @logdev.nil? || severity < level
+
+      if message.nil?
+        if block_given?
+          message  = yield
+        else
+          message  = progname
+          progname = @progname
+        end
+      end
+
+      @logdev.write \
+        format_message(format_severity(severity), Time.now, progname, message)
     end
   end
 end

activesupport/test/logger_test.rb

@@ -144,6 +144,19 @@ class LoggerTest < ActiveSupport::TestCase
     assert_includes @output.string, "THIS IS HERE"
   end
 
+  def test_unsilencing
+    @logger.level = Logger::INFO
+
+    @logger.debug "NOT THERE"
+
+    @logger.silence Logger::DEBUG do
+      @logger.debug "THIS IS HERE"
+    end
+
+    assert_not @output.string.include?("NOT THERE")
+    assert_includes @output.string, "THIS IS HERE"
+  end
+
   def test_logger_silencing_works_for_broadcast
     another_output  = StringIO.new
     another_logger  = ActiveSupport::Logger.new(another_output)