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Only raise DelegationError if it's is the source of the exception

This fixes situations where nested NoMethodError exceptions are masked
by delegations. This would cause confusion especially where there was a
problem in the Rails booting process because of a delegation in the
routes reloading code.

Fixes #10559
(cherry picked from commit 07a4c76)

Conflicts:
	activesupport/CHANGELOG.md
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1 parent 88d1fa4 commit 8dec2e7281a1b38db037dc23becd1a147d1fcae1 @pixeltrix pixeltrix committed Jul 11, 2013
@@ -1,5 +1,9 @@
## unreleased ##
+* Only raise `Module::DelegationError` if it's the source of the exception.
+
+ Fixes #10559
+
* Add `DateTime#usec` and `DateTime#nsec` so that `ActiveSupport::TimeWithZone` keeps
sub-second resolution when wrapping a `DateTime` value.
Fixes #10855
@@ -179,16 +179,17 @@ def #{method_prefix}#{method}(#{definition}) # def customer_name(*args, &
exception = %(raise "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")
module_eval(<<-EOS, file, line - 2)
- def #{method_prefix}#{method}(#{definition}) # def customer_name(*args, &block)
- _ = #{to} # _ = client
- _.#{method}(#{definition}) # _.name(*args, &block)
- rescue NoMethodError # rescue NoMethodError
- if _.nil? # if _.nil?
- #{exception} # # add helpful message to the exception
- else # else
- raise # raise
- end # end
- end # end
+ def #{method_prefix}#{method}(#{definition}) # def customer_name(*args, &block)
+ _ = #{to} # _ = client
+ _.#{method}(#{definition}) # _.name(*args, &block)
+ rescue NoMethodError => e # rescue NoMethodError => e
+ location = "%s:%d:in `%s'" % [__FILE__, __LINE__ - 2, '#{method_prefix}#{method}'] # location = "%s:%d:in `%s'" % [__FILE__, __LINE__ - 2, 'customer_name']
+ if _.nil? && e.backtrace.first == location # if _.nil? && e.backtrace.first == location
+ #{exception} # # add helpful message to the exception
+ else # else
+ raise # raise
+ end # end
+ end # end
EOS
end
end
@@ -66,6 +66,23 @@ def self.table_name
delegate :name, :to => :client, :prefix => false
end
+Product = Struct.new(:name) do
+ delegate :name, :to => :manufacturer, :prefix => true
+ delegate :name, :to => :type, :prefix => true
+
+ def manufacturer
+ @manufacturer ||= begin
+ nil.unknown_method
+ end
+ end
+
+ def type
+ @type ||= begin
+ nil.type_name
+ end
+ end
+end
+
class ParameterSet
delegate :[], :[]=, :to => :@params
@@ -264,6 +281,16 @@ def test_delegation_invokes_the_target_exactly_once
assert_equal [3], se.ints
end
+ def test_delegation_doesnt_mask_nested_no_method_error_on_nil_receiver
+ product = Product.new('Widget')
+
+ # Nested NoMethodError is a different name from the delegation
+ assert_raise(NoMethodError) { product.manufacturer_name }
+
+ # Nested NoMethodError is the same name as the delegation
+ assert_raise(NoMethodError) { product.type_name }
+ end
+
def test_parent
assert_equal Yz::Zy, Yz::Zy::Cd.parent
assert_equal Yz, Yz::Zy.parent

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