[ruby-core:116107] [Ruby master Bug#20158] Ractor affects Coverage results

Issue #20158 has been updated by mame (Yusuke Endoh).





@janosch-x Could you explain the complete reproduction procedure? I couldn'=
t reproduce the issue by the following configuration.



test.rb

```ruby

Ractor.new { nil }



require "coverage"



Coverage.start



load "test2.rb"

foo



pp Coverage.result

```



test2.rb

```ruby

def foo

  1

end

```



```

$ ruby test.rb

test.rb:1: warning: Ractor is experimental, and the behavior may change in =
future versions of Ruby! Also there are many implementation issues.

{"test2.rb"=3D>[1, 1, nil]}

```



Indeed, coverage does not support Ractor (#20167). However, I don't underst=
and why just creating a Ractor affects coverage.



----------------------------------------

Bug #20158: Ractor affects Coverage results

https://bugs.ruby-lang.org/issues/20158#change-106101



* Author: janosch-x (Janosch M=FCller)

* Status: Open

* Priority: Normal

* ruby -v: ruby 3.3.0preview1 (2023-05-12 master a1b01e7701) [arm64-darwin2=
2]

* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

----------------------------------------

I have a large rspec test suite. I found that if I call a Ractor, the Cover=
age results are strongly affected, i.e. almost all files appear to be uncov=
ered. This happens even if I only ever call a Ractor before the library or =
rspec are required.



Unfortunately, I was not able to build a simple repro yet.



I assume it is a timing thing and only affects larger suites, or it only ha=
ppens if there are multiple files, and maybe if the library lazily requires=
 its sub-modules?



However, I guess this should produce the same results when added to the spe=
c_helper.rb of other large suites:



```ruby

# Ractor.new { nil } # uncomment this to affect coverage results



require 'coverage'

Coverage.start



# require library, set up rspec etc.=20



RSpec.configuration.after(:suite) do

  # this number is greatly reduced and unstable when calling Ractor above

  p Coverage.result.values.sum { |arr| arr.sum(&:to_i) }

end

```



I had this problem in [this library](https://github.com/jaynetics/character=
_set/). The problem affects simplecov users as well, as described [here](ht=
tps://github.com/simplecov-ruby/simplecov/issues/1058).







--=20

https://bugs.ruby-lang.org/

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