Require Ruby 2.6

[ibrahima]

I was trying to use this gem on Ruby 2.5 (sigh) and ran into an issue. It turns out that it calls then on a Hash, which was added in Ruby 2.6. I figured it would be helpful to document this explicitly, though hopefully there aren't a lot of people out there running 2.5.

https://til.hashrocket.com/posts/f4agttd8si-chaining-then-in-ruby-26

[rubys]

If .then is just an alias, and .then is only used twice that i can find, why not change both occurrences to .yield_self?

[ibrahima]

Yeah that'd work too, I can make that change later. I didn't know if it was intentional or if there are any other dependencies on 2.6.

[ibrahima]

@rubys done! I haven't tested this on Ruby 2.5 yet but it seems like it should work now...

Actually... maybe not. I now get this error, so maybe there's an issue with 2.5's version of ERB. Maybe something changed with how it handles partials? I'm confused since the syntax seems pretty normal to me... 🤷🏾.

	 5: from /usr/local/lib/ruby/2.5.0/erb.rb:876:in `result'
	 4: from /usr/local/lib/ruby/2.5.0/erb.rb:876:in `eval'
	 3: from /home/user/.bundle/ruby/2.5.0/dockerfile-rails-87c256966bdf/lib/generators/templates/Dockerfile.erb:39:in `template'
	 2: from /home/user/.bundle/ruby/2.5.0/dockerfile-rails-87c256966bdf/lib/generators/dockerfile_generator.rb:342:in `render'
	 1: from /usr/local/lib/ruby/2.5.0/erb.rb:874:in `result'
/usr/local/lib/ruby/2.5.0/erb.rb:872:in `block in result': no implicit conversion of Hash into Integer (TypeError)

The template line in question:

https://github.com/fly-apps/dockerfile-rails/blob/main/lib/generators/templates/Dockerfile.erb#L39

The part of ERB that's raising the error though I don't really understand why: https://github.com/ruby/ruby/blob/b7f19dd8419aa10c8bc3dfb8181a2caafe0d81d9/lib/erb.rb#L874

Personally... I'm not very invested in making this work on 2.5, I am in the process of upgrading anyway, and I can run the generator with 2.6 even if I'm building a 2.5 Docker image at the moment. Do you think it makes sense to just update the gemspec to specify 2.6+ for now? Thanks! I do really like this gem overall.

[rubys]

Fix the RuboCop failure and I'll merge the change.

[ibrahima]

Thanks! I left change of the alias method in for now, hope that's okay. If I get some time to figure out why it's not working on 2.5 I may submit another PR and loosen the restriction, but for now this should probably help some confusion for people on old Ruby versions.