rubocop-ast release made rubocop 1.6.1 require ruby 2.5.0

[mmb]

rubocop version 1.6.1 has dependency constraint:

rubocop-ast >= 1.2.0, < 2.0

The recent releases of rubocop-ast (1.4.2 and 1.5.0) satisfy these constraints so they introduce a dependency on ruby version >= 2.5.0. This breaks rubocop version 1.6.1 on ruby 2.4.

---

Expected behavior

It's unexpected that released versions of rubocop would change their ruby version requirements. Should a ruby version bump in rubocop-ast be treated as a major version?

Actual behavior

$ ruby -v
ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-darwin19]
$ gem install rubocop -v 1.6.1
Fetching: parser-3.0.1.1.gem (100%)
Successfully installed parser-3.0.1.1
Fetching: rubocop-ast-1.5.0.gem (100%)
ERROR:  Error installing rubocop:
	rubocop-ast requires Ruby version >= 2.5.0.

Steps to reproduce the problem

Install rubocop version 1.6.1 when using ruby 2.4.2.

RuboCop version

[bbatsov]

Should a ruby version bump in rubocop-ast be treated as a major version?

We discussed the subject here for RuboCop #9648, but I guess we didn't consider the impact for rubocop-ast.

[bbatsov]

Just to be clear - our expectations was that in a case like yours you'd the get the news version of rubocop-ast that's installable on Ruby 2.4. I'm not sure why that's not actually happening.

[marcandre]

Sorry you're having issues.

Indeed, it shouldn't be breaking.

This may be a bug in the rubygems you are using that has been fixed? Could you try gem update --system first?

I was able to install rubocop both 1.12.1 and 1.6.1 on Ruby 2.4.10 with:

$ gem update --system
[...]
$ gem install rubocop
Fetching rexml-3.2.5.gem
Fetching unicode-display_width-2.0.0.gem
Fetching ruby-progressbar-1.11.0.gem
Fetching parser-3.0.1.1.gem
Fetching rubocop-ast-1.4.1.gem
Fetching rubocop-1.12.1.gem
Fetching rainbow-3.0.0.gem
Fetching parallel-1.20.1.gem
Fetching regexp_parser-2.1.1.gem
Successfully installed unicode-display_width-2.0.0
Successfully installed ruby-progressbar-1.11.0
Successfully installed parser-3.0.1.1
Successfully installed rubocop-ast-1.4.1
Successfully installed rexml-3.2.5
Successfully installed regexp_parser-2.1.1
Successfully installed rainbow-3.0.0
Successfully installed parallel-1.20.1
Successfully installed rubocop-1.12.1
9 gems installed
$ gem install rubocop -v 1.6.1
Fetching rubocop-1.6.1.gem
Fetching unicode-display_width-1.7.0.gem
Successfully installed unicode-display_width-1.7.0
Successfully installed rubocop-1.6.1
2 gems installed
$ ruby -v
ruby 2.4.10p364 (2020-03-31 revision 67879) [x86_64-darwin18]

[mmb]

gem update --system does fix it. Thanks for the responses.

docker run -it ruby:2.4.10 bash
gem install rubocop -v 1.6.1
ERROR:  Error installing rubocop:
	The last version of rubocop-ast (>= 1.2.0, < 2.0) to support your Ruby & RubyGems was 1.4.1. Try installing it with `gem install rubocop-ast -v 1.4.1` and then running the current command again
	rubocop-ast requires Ruby version >= 2.5.0. The current ruby version is 2.4.10.364.
gem update --system
gem install rubocop -v 1.6.1
Fetching rubocop-ast-1.4.1.gem
Successfully installed unicode-display_width-1.7.0
Successfully installed ruby-progressbar-1.11.0
Successfully installed rubocop-ast-1.4.1
Successfully installed rubocop-1.6.1
4 gems installed