Remove activerecord from runtime dependencies

[flash-gordon]

Hey @mcmire!

It took a while but I came back.
This PR removes activerecord from runtime dependencies and runs tests in an AR-free environment to make sure activesupport doesn't interfere with the gem (I removed one .blank? usage along the way).
I didn't move code, just tagged specs and added a filter. I think you know better if tests require re-organization.
Side note: ruby 2.7 changed the meaning of .object_id, it's not related to memory address anymore. Since I locally tested on 2.7, I added a hacky helper to get an object address on the newest ruby version. Read https://bugs.ruby-lang.org/issues/15408 and https://bugs.ruby-lang.org/issues/15626#Object-ID for details. There's still one more usage of object_id in the sources, you probably want to update it too. My nasty approach works for testing, but for gem's code it can be less desirable.
I didn't add 2.7 to the matrix, I think it should be done separately. Did you think about migrating to GH actions btw?

[mcmire]

Some minor comments from me here. Nice work!

[mcmire]

Oh and in response to your last comments above:

There's still one more usage of object_id in the sources, you probably want to update it too.

Okay, that's fine. I'll look more closely at what you did to see if there's another way.

I didn't add 2.7 to the matrix, I think it should be done separately.

That's fine with me.

Did you think about migrating to GH actions btw?

Yes, I tried to get Actions working when I first set up CI, but was unsuccessful. There's something about the cache action that didn't seem to be working for me, I don't know if it's a bug or what. I also don't know (or remember at the moment) how concurrency works with Actions. I've used Travis for previous projects and the matrix there makes sense to me. That said, I wouldn't mind getting Actions working eventually. There'd be one fewer place to look.

[flash-gordon]

@mcmire GH actions now have matrix too, it's basically the same as it was on Travis. Here's a sample working config https://github.com/dry-rb/dry-types/blob/master/.github/workflows/ci.yml

[flash-gordon]

@mcmire I addressed your comments

[mcmire]

@flash-gordon Thanks so much!

[mcmire]

v0.4.0 is now out with this change!

[flash-gordon]

Awesome! 🎉

[Mange]

This seems to have broken our build.

[2020-01-22T05:21:33.596Z] Failure/Error: require "super_diff/rspec-rails"

[2020-01-22T05:21:33.596Z] 

[2020-01-22T05:21:33.596Z] NameError:

[2020-01-22T05:21:33.596Z]   uninitialized constant ActiveRecord

[2020-01-22T05:21:33.596Z]   Did you mean?  ActiveModel

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/active_record/monkey_patches.rb:2:in `<top (required)>'

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/active_record.rb:39:in `require'

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/active_record.rb:39:in `<top (required)>'

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/rails.rb:1:in `require'

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/rails.rb:1:in `<top (required)>'

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/rspec-rails.rb:2:in `require'

[2020-01-22T05:21:33.596Z] # /usr/local/bundle/ruby/2.6.0/gems/super_diff-0.4.0/lib/super_diff/rspec-rails.rb:2:in `<top (required)>'

[2020-01-22T05:21:33.596Z] # ./spec/spec_helper.rb:11:in `require'

[2020-01-22T05:21:33.596Z] # ./spec/spec_helper.rb:11:in `<top (required)>'

Do we need to change some of the setup code?

[flash-gordon]

@Mange to me it's unlikely changes in this PR are related. However, I think super_diff should require activerecord files itself, could you report this issue to the main repo?

[flash-gordon]

#65 this is related

[Mange]

Thanks. I opened #68 to track this issue.