Bug #20716
openDifferent instance_method behavior in Ruby 2.7 and Ruby 3.x
Description
Hi, I am working on upgrading our project from 2.7 to 3.x and found a breaking change in instance_method
behavior.
Here is the code snippet
module A
def test(*args)
super
end
end
module B
def test(a)
puts a
end
end
B.prepend(A)
a = lambda do
puts 'lambda'
end
class C
include B
end
B.instance_method(:test).bind(C.new).call(1)
# Ruby 2.7: 1
# Ruby 3.0: 1
# Ruby 3.1: 1
B.module_exec do
define_method(:test, a)
end
B.instance_method(:test).bind(C.new).call
# Ruby 2.7: lambda
# Ruby 3.0: wrong number of arguments (given 0, expected 1) (ArgumentError)
# Ruby 3.1: wrong number of arguments (given 0, expected 1) (ArgumentError)
I don't know if this is a bug or a correct intention.
My specs:
- Ruby manager: rbenv
- Tested on
- ruby 2.7.4p191 (2021-07-07 revision a21a3b7d23) [x86_64-linux]
- ruby 3.0.7p220 (2024-04-23 revision 724a071175) [x86_64-linux]
- ruby 3.1.4p223 (2023-03-30 revision 957bb7cb81) [x86_64-linux]
- ruby 3.2.3 (2024-01-18 revision 52bb2ac0a6) [x86_64-linux]
- ruby 3.3.1 (2024-04-23 revision c56cd86388) [x86_64-linux]
Updated by jeremyevans0 (Jeremy Evans) 6 days ago
This appears to be a method caching bug in super
. If you remove the .call(1)
, then it works correctly. super_method
returns the correct method. The define_method(:test, a)
call should result in the method cache being cleared or ignored, but it doesn't. However, it isn't specific to define_method
, regular def
results in the same behavior.
Maybe related? b9007b6c548f91e88fd3f2ffa23de740431fa969
Updated by natton (Tien Truong) 6 days ago
Yes, you are correct. This isn't specific to define_method
. I modified the snippet a little bit
module A
def test(*args)
super
end
end
module B
def test(a)
puts a
end
end
B.prepend(A)
class C
include B
end
C.new.test(1)
# Ruby 2.7: 1
# Ruby 3.0: 1
# Ruby 3.1: 1
module B
def test
puts 'new test'
end
end
C.new.test
# Ruby 2.7: 'new test'
# Ruby 3.0: wrong number of arguments (given 0, expected 1) (ArgumentError)
# Ruby 3.1: wrong number of arguments (given 0, expected 1) (ArgumentError)
Updated by jeremyevans0 (Jeremy Evans) 5 days ago
This behavior isn't related to instance_method
. It occurs in the following code:
module A
def test(*args)
super
end
end
module B
def test(a)
puts a
end
end
class C; end
B.prepend(A)
C.include(B)
C.new.test 1
module B
def test
puts 'lambda'
end
end
C.new.test
It also happens when you replace C.include(B)
with C.prepend(B)
.
It does not happen when you replace B.prepend(A); C.include(B)
with A.include(B); C.include(A)
. It also does not happen if a class directly prepends a module, such as in this example:
module A
def test(*args)
super
end
end
class B
def test(a)
puts a
end
end
B.prepend(A)
B.new.test 1
class B
def test
puts 'lambda'
end
end
B.new.test
It seems like the conditions are:
- Class includes or prepends module X that prepends module Y
- Both X and Y define method M
- Y's definition of M calls
super
- X's definition of M is overridden after
super
method call is cached
Updated by natton (Tien Truong) 3 days ago
Hi Evans,
Thank you for your confirmation.
I am new here so is there anything I can do to escalate this or how can I help to resolve this issue?
Updated by jeremyevans0 (Jeremy Evans) 3 days ago
natton (Tien Truong) wrote in #note-4:
I am new here so is there anything I can do to escalate this or how can I help to resolve this issue?
There isn't an escalation process in place in Ruby, as it is an open source project managed by volunteers. In terms of helping to resolve the issue, first, we need to determine the cause of the bug. Bisecting changes between 2.7 and 3.0 would help here to confirm the actual commit that caused the issue (the commit I listed in an early comment is just a guess). I tried bisecting myself, but I think the current version of bison doesn't work with the parse.y of 2.7, so bisecting is more challenging than usual.
After the problem has been determined, then an appropriate fix needs to be determined. This is likely more challenging, and requires knowledge and/or study of how method caching works in Ruby.
If this isn't work you are comfortable doing yourself, and it's important enough that you are willing to pay to have it fixed, you could pay a developer to do so on your behalf, or you could offer a bounty for a developer to fix it for you. There are no guarantees of success, of course, but it likely increases the odds.
Considering this bug has been around for about 4 years, and this is the first time it has been reported, this doesn't seem like a major issue, and it should be fairly easy to work around by overriding the method before calling super
. That said, I would still like to see it fixed, and likely will work on it more myself at some point. However, I don't have extensive knowledge of Ruby's method caching, and there are other bugs I'm working on fixing.
Updated by jeremyevans0 (Jeremy Evans) 1 day ago
- Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN to 3.1: REQUIRED, 3.2: REQUIRED, 3.3: REQUIRED
I was able to track down the cause and submitted a pull request to fix this: https://github.com/ruby/ruby/pull/11582
It appears to be introduced by ad729a1d11c6c57efd2e92803b4e937db0f75252, which I wrote and which was a fix for #16736.
Updated by natton (Tien Truong) 1 day ago
Hi Evans,
Thank you for your guidance and the quick fix.
I truly appreciate it