[Fix #8006] Fix infinite loop for Style/IfUnlessModifier

[tejasbubane]

Closes #8006
Closes #8025
Closes #7969

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[joe-p]

The following line will still produce an infinite loop with this commit pulled into master:

puts "                                                                                                    #{' ' if true}"

$ rubocop -ad test.rb
For /home/joe/rubo_test/test: Default configuration from /home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/config/default.yml
Inspecting 1 file
Scanning /home/joe/rubo_test/test/test.rb
C

Offenses:

test.rb:3:109: C: [Corrected] Style/IfUnlessModifier: Favor modifier if usage when having a single-line body. Another good alternative is the usage of control flow &&/||.
puts "                                                                                                    #{if true
                                                                                                            ^^
test.rb:3:113: C: [Corrected] Style/IfUnlessModifier: Modifier form of if makes the line too long.
puts "                                                                                                    #{' ' if true}"
                                                                                                                ^^

0 files inspected, 2 offenses detected, 2 offenses corrected
Infinite loop detected in /home/joe/rubo_test/test/test.rb.
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:290:in `check_for_infinite_loop'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:273:in `block in iterate_until_no_changes'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:272:in `loop'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:272:in `iterate_until_no_changes'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:243:in `do_inspection_loop'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:122:in `block in file_offenses'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:146:in `file_offense_cache'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:120:in `file_offenses'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:111:in `process_file'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:90:in `block in each_inspected_file'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:89:in `each'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:89:in `reduce'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:89:in `each_inspected_file'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:78:in `inspect_files'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/runner.rb:39:in `run'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli/command/execute_runner.rb:21:in `execute_runner'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli/command/execute_runner.rb:13:in `run'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli/command.rb:10:in `run'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli/environment.rb:17:in `run'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli.rb:65:in `run_command'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli.rb:72:in `execute_runners'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/lib/rubocop/cli.rb:41:in `run'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/exe/rubocop:13:in `block in <top (required)>'
/home/joe/.rvm/rubies/ruby-2.7.1/lib/ruby/2.7.0/benchmark.rb:308:in `realtime'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/gems/rubocop-0.84.0/exe/rubocop:12:in `<top (required)>'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/bin/rubocop:23:in `load'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/bin/rubocop:23:in `<main>'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/bin/ruby_executable_hooks:24:in `eval'
/home/joe/.rvm/gems/ruby-2.7.1@kisscraft/bin/ruby_executable_hooks:24:in `<main>'
Finished in 0.10348649999991721 seconds

[tejasbubane]

@joe-p Now it should not.

[koic]

An infinite loop error is caused by a combination of cops. Con you add a reproduction test for infinite loop error to spec/rubocop/cli/cli_autocorrect_spec.rb? E.g.: https://github.com/rubocop-hq/rubocop/pull/7901/files#diff-0e7dbdd6e99e0defc2bab2cb544b42da
And I think the description of this test better to be updated to not register an offense.

[iGEL]

I'd love to see this merged. Is there anything I could help with?

[tejasbubane]

@iGEL I missed @koic's comment. Working on it now.

[marcandre]

I also opened #8283 (but didn't know about this)

As I wrote there, I feel it is imperative that the code that builds the replacement string should be used for the calculation length.

The same bugs exist for WhileUntilModifier too.

The refactoring I made yesterday should help a bit.

[tejasbubane]

I feel it is imperative that the code that builds the replacement string should be used for the calculation length.

I agree with @marcandre's approach. Closing this for now.