Bug #20158


Ractor affects Coverage results

Added by janosch-x (Janosch Müller) 6 months ago. Updated 5 months ago.

Target version:
ruby -v:
ruby 3.3.0preview1 (2023-05-12 master a1b01e7701) [arm64-darwin22]


I have a large rspec test suite. I found that if I call a Ractor, the Coverage results are strongly affected, i.e. almost all files appear to be uncovered. 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 happens 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 spec_helper.rb of other large suites:

# { nil } # uncomment this to affect coverage results

require 'coverage'

# require library, set up rspec etc. 

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) }

I had this problem in this library. The problem affects simplecov users as well, as described here.

Related issues 1 (1 open0 closed)

Has duplicate Ruby master - Bug #20167: Code execution isn't recorded in RactorOpenActions

Updated by mame (Yusuke Endoh) 5 months ago

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

test.rb { nil }

require "coverage"


load "test2.rb"

pp Coverage.result


def foo
$ 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"=>[1, 1, nil]}

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

Actions #2

Updated by jeremyevans0 (Jeremy Evans) 5 months ago

  • Has duplicate Bug #20167: Code execution isn't recorded in Ractor added

Updated by janosch-x (Janosch Müller) 5 months ago

Hi @mame (Yusuke Endoh)!

As mentioned in the ticket, i could not reproduce it with a smaller setup.

Maybe problems only begin at a certain size, or when there is some require hierarchy?

I've now forked my affected repository to demonstrate the problem:

Maybe you have some idea how to debug it based on this?

Updated by mame (Yusuke Endoh) 5 months ago

  • Status changed from Open to Assigned
  • Assignee set to ko1 (Koichi Sasada)

Thanks, I reproduce the problem successfully with rspec + Ractor + TracePoint (without coverage).

# test_spec.rb
if ENV["RACTOR"] == "1" { nil }
  p :ractor_enabled
  p :ractor_disabled

$tp = {|t| pp t }

describe "foo" do

Expected behavior: The last output should be the line of $tp.disable as follows.

$ RACTOR=0 rspec t_spec.rb
#<TracePoint:line /home/mame/.rbenv/versions/ruby-dev/lib/ruby/gems/3.4.0+0/gems/rspec-core-3.12.2/lib/rspec/core/example_group.rb:398 in `subclass'>
#<TracePoint:line /home/mame/work/ractor_coverage_repro/t_spec.rb:12>
#<TracePoint:line <internal:trace_point>:297 in `disable'>
No examples found.

Finished in 0.00022 seconds (files took 7.97 seconds to load)
0 examples, 0 failures

Actual result: Once Ractor mode is enabled, TracePoint stops firing in the middle of the process.

$ RACTOR=1 rspec t_spec.rb
#<TracePoint:line /home/mame/.rbenv/versions/ruby-dev/lib/ruby/3.4.0+0/rubygems/basic_specification.rb:208 in `internal_init'>
#<TracePoint:line /home/mame/.rbenv/versions/ruby-dev/lib/ruby/3.4.0+0/rubygems/basic_specification.rb:209 in `internal_init'>
#<TracePoint:line /home/mame/.rbenv/versions/ruby-dev/lib/ruby/3.4.0+0/rubygems/stub_specification.rb:73 in `initialize'>
#<TracePoint:line /home/mame/.rbenv/versions/ruby-dev/lib/ruby/3.4.0+0/rubygems/stub_specification.rb:74 in `initialize'>
No examples found.

Finished in 0.00027 seconds (files took 0.101 seconds to load)
0 examples, 0 failures

Assigning to @ko1 (Koichi Sasada)

Updated by luke-gru (Luke Gruber) 5 months ago

It sounds like this bug is related to


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