Debug gem conflict with rspec mocks

Start with lib/debug/source_repository.rb:38 and run the Ruby 3.3.7 reproduction from the issue with debug 1.11.0 and RSpec. Trace how the File.exist? call interacts with the configured mock. Done means the reproduction passes without mock expectation errors while preserving the source repository behavior.

Your environment

• ruby -v: ruby 3.3.7
• rdbg -v: 1.11.0

Describe the bug
The debug gem's method in debug/source_repository.rb:38 calls File.exist?, which interferes with RSpec mocks that stub this method for specific file paths. This causes test failures with mock expectation errors when the debug gem is loaded during test execution.

To Reproduce

system('gem install bundler') unless Gem::Specification::find_all_by_name('bundler').any?
require 'bundler/inline'

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rspec'
  gem 'debug', '~> 1.11.0'
end

require 'rspec'
require 'debug'

class MyClass
  def check_if_file_exist?(path)
    File.exist?(path)
  end
end

RSpec.describe "debug gem + File.exist? conflict" do
  let(:target_path) { "config/session_store.yml" }

  let(:my_class) { MyClass.new }

  before do
    allow(File).to receive(:exist?).with(target_path).and_return(true)
  end

  it "stubs File.exist? and avoids debug interference" do
    result = my_class.check_if_file_exist?(target_path)

    expect(result).to be true
  end
end

RSpec::Core::Runner.run([])

Expected behavior
A clear and concise description of what you expected to happen.

• The test should pass