Froze rails gems

[depot.git] / vendor / rails / activesupport / lib / active_support / whiny_nil.rb

diff --git a/vendor/rails/activesupport/lib/active_support/whiny_nil.rb b/vendor/rails/activesupport/lib/active_support/whiny_nil.rb
new file mode 100644 (file)
index 0000000..36fe951
--- /dev/null
+++ b/vendor/rails/activesupport/lib/active_support/whiny_nil.rb
@@ -0,0 +1,58 @@
+# Extensions to +nil+ which allow for more helpful error messages for people who
+# are new to Rails.
+#
+# Ruby raises NoMethodError if you invoke a method on an object that does not
+# respond to it:
+#
+#   $ ruby -e nil.destroy
+#   -e:1: undefined method `destroy' for nil:NilClass (NoMethodError)
+#
+# With these extensions, if the method belongs to the public interface of the
+# classes in NilClass::WHINERS the error message suggests which could be the
+# actual intended class:
+#
+#   $ script/runner nil.destroy 
+#   ...
+#   You might have expected an instance of ActiveRecord::Base.
+#   ...
+#
+# NilClass#id exists in Ruby 1.8 (though it is deprecated). Since +id+ is a fundamental
+# method of Active Record models NilClass#id is redefined as well to raise a RuntimeError
+# and warn the user. She probably wanted a model database identifier and the 4
+# returned by the original method could result in obscure bugs.
+#
+# The flag <tt>config.whiny_nils</tt> determines whether this feature is enabled.
+# By default it is on in development and test modes, and it is off in production
+# mode.
+class NilClass
+  WHINERS = [::Array]
+  WHINERS << ::ActiveRecord::Base if defined? ::ActiveRecord
+
+  METHOD_CLASS_MAP = Hash.new
+
+  WHINERS.each do |klass|
+    methods = klass.public_instance_methods - public_instance_methods
+    class_name = klass.name
+    methods.each { |method| METHOD_CLASS_MAP[method.to_sym] = class_name }
+  end
+
+  # Raises a RuntimeError when you attempt to call +id+ on +nil+.
+  def id
+    raise RuntimeError, "Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id", caller
+  end
+
+  private
+    def method_missing(method, *args, &block)
+      raise_nil_warning_for METHOD_CLASS_MAP[method], method, caller
+    end
+
+    # Raises a NoMethodError when you attempt to call a method on +nil+.
+    def raise_nil_warning_for(class_name = nil, selector = nil, with_caller = nil)
+      message = "You have a nil object when you didn't expect it!"
+      message << "\nYou might have expected an instance of #{class_name}." if class_name
+      message << "\nThe error occurred while evaluating nil.#{selector}" if selector
+
+      raise NoMethodError, message, with_caller || caller
+    end
+end
+