Missing TracePoint return event for ||=
While updating ruby-prof, I ran into an issue while profiling rails that caused ruby-prof to show an incorrect method invocation tree. This is caused by the use of the ||= operator in minitest.
Here is a small test case:
class Operators def self.should_be_called_by_test end def self.test self.a should_be_called_by_test end def self.b=(value) end def self.b end def self.a self.b ||= :random end end tp = TracePoint.new(:call, :c_call, :return, :c_return) do |event| p [event.event, event.method_id] end tp.enable do Operators.test end
This is the result:
[:call, :test] [:call, :a] [:call, :b] [:return, :b] [:call, :b=] [:return, :b=] <---------- Missing [:return, :a] [:call, :should_be_called_by_test] [:return, :should_be_called_by_test] [:return, :test]
Notice there is a missing :return event for the :a method. From my experiments, ||= works if the left hand side is not a method call (say @b ||=1) but fails if it is.
Note this works correctly on the latest version of ruby 2.5 - ruby 2.5.5p157 (2019-03-15 revision 67260) [x86_64-darwin18].
The minitest code which this bug is triggered by:
module ActiveSupport class TestCase < ::Minitest::Test Assertion = Minitest::Assertion class << self def test_order=(new_order) ActiveSupport.test_order = new_order end def test_order ActiveSupport.test_order ||= :random end end end end