Initial import.

MIT-LICENSE

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+Copyright (c) 2010 [name of plugin creator]
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README

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+BetterLocking
+=============
+
+Introduction goes here.
+
+
+Example
+=======
+
+Example goes here.
+
+
+Copyright (c) 2010 [name of plugin creator], released under the MIT license

Rakefile

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+require 'rake'
+require 'rake/testtask'
+require 'rake/rdoctask'
+
+desc 'Default: run unit tests.'
+task :default => :test
+
+desc 'Test the better_locking plugin.'
+Rake::TestTask.new(:test) do |t|
+  t.libs << 'lib'
+  t.libs << 'test'
+  t.pattern = 'test/**/*_test.rb'
+  t.verbose = true
+end
+
+desc 'Generate documentation for the better_locking plugin.'
+Rake::RDocTask.new(:rdoc) do |rdoc|
+  rdoc.rdoc_dir = 'rdoc'
+  rdoc.title    = 'BetterLocking'
+  rdoc.options << '--line-numbers' << '--inline-source'
+  rdoc.rdoc_files.include('README')
+  rdoc.rdoc_files.include('lib/**/*.rb')
+end

init.rb

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+require 'better_locking'

install.rb

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+# Install hook code here

lib/better_locking.rb

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+module BetterLocking 
+
+  def self.included(base)
+    base.extend(ClassMethods)
+  end
+
+  def confirm_lock!
+    raise LockNotHeld unless ActiveRecord::Base.locked_objects.include?(self)
+  end
+
+  module ClassMethods
+    def transaction_with_locks(*objects)
+      objects = objects.flatten.compact
+      return if objects.all? {|object| ActiveRecord::Base.locked_objects.include?(object) }
+
+      minimum_transaction_level = (Rails.env.test? ? 1 : 0)
+      raise LockMustBeOutermostTransaction unless connection.open_transactions == minimum_transaction_level
+
+      objects.sort_by {|object| [object.class.name, object.send(object.class.primary_key)] }
+      begin
+        ActiveRecord::Base.locked_objects = nil
+        transaction do
+          begin
+            objects.each(&:lock!)
+            ActiveRecord::Base.locked_objects = objects
+          rescue ActiveRecord::StatementInvalid => exception
+            if exception.message =~ /Deadlock/
+              raise RetryTransaction
+            else
+              raise
+            end
+          end
+
+          yield
+        end
+      rescue RetryTransaction
+        retry
+      ensure
+        ActiveRecord::Base.locked_objects = nil
+      end
+    end
+
+    def locked_objects=(objects)
+      @locked_objects = objects
+    end
+
+    def locked_objects
+      @locked_objects || []
+    end
+  end
+
+  class LockMustBeOutermostTransaction < RuntimeError
+  end
+
+  class LockNotHeld < RuntimeError
+  end
+
+  class RetryTransaction < RuntimeError
+  end
+
+end
+
+class ActiveRecord::Base
+  include BetterLocking
+end

tasks/better_locking_tasks.rake

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+# desc "Explaining what the task does"
+# task :better_locking do
+#   # Task goes here
+# end

test/better_locking_test.rb

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+require 'test_helper'
+
+class BetterLockingTest < ActiveSupport::TestCase
+  # Replace this with your real tests.
+  test "the truth" do
+    assert true
+  end
+end

test/test_helper.rb

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+require 'rubygems'
+require 'active_support'
+require 'active_support/test_case'

uninstall.rb

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+# Uninstall hook code here