Compatibility with Ruby 2.0+

[bbonamin]

First of all, let me express how grateful I am for this gem. I've recently been learning about react and webpack, and react_on_rails has made it a breeze to implement what I've learned in my Rails projects! It's allowed us to add "sprinkles" of React in certain Rails views, without commiting to rewriting everything from scratch. Thank you!

Now, for a project I'm currently working on, we need compatibility with Ruby 2.0 (yeah yeah, I know it's not receiving fixes or patches anymore, but we can't upgrade yet.)

The rubygems page for react_on_rails doesn't specify a minimum ruby version, but if you try to use the gem with < 2.1, it breaks because of the required keyword arguments that were introduced in 2.1.

The changes in this PR do "backport" this behavior to 2.0. I couldn't find anything else other than these syntax changes that would make the gem incompatible with 2.0, and tests seem to pass.

Thoughts?

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This change is 

[bbonamin]

Something seems to be up with TravisCI trying to install fsevents, which is not compatible with Linux. The build was green when I removed it from the npm shrinkwrap file on my fork, but of course that was a change that I didn't want to include in this pull request.

EDIT: Seems to be related to this issue npm/npm#14042, and it's apparently fixable by downgrading npm or running shinkrwrap again with npm 3.10.10+

[coveralls]

Coverage remained the same at 82.75% when pulling 52e2915 on bbonamin:ruby20 into 93fb10b on shakacode:master.

[coveralls]

Coverage remained the same at 82.75% when pulling 137d186 on bbonamin:ruby20 into 93fb10b on shakacode:master.

[coveralls]

Coverage remained the same at 82.75% when pulling a458267 on bbonamin:ruby20 into 93fb10b on shakacode:master.

[justin808]

@samnang @mapreal19 @robwise This one looks OK to me. Ugly, but I guess some people need it.

I vote for this one. How about you guys?

[samnang]

@justin808 To me, it's okay if we want to support them for a while and pay attention of features that might break for this, but it shouldn't a long term because Rails 5 already drop their support. If we just trying with minimum dependency on Rails, then it might not be a problem.

[mapreal19]

@justin808 @bbonamin we could remove the duplication for those required arguments with a helper method. Take a look at this answer http://stackoverflow.com/a/15078852/2273578

I would rather see those methods like this:

def  rails_context(server_side: required) 

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Review status: 0 of 7 files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[robwise]

lol I vote for this just the way I voted for it the last time someone did this almost a year ago, this repo really hardly uses keyword arguments so it's a no-brainer to keep it backwards compatible. I'm not sure why we keep re-introducing breaking changes:

https://github.com/shakacode/react_on_rails/blob/28776cbc36b22dc3aa91a5b1fe9f9b2b3c20fdc7/CHANGELOG.md#210---2016-01-26

[bbonamin]

@mapreal19 I've pushed a change with a DRYer approach to doing to required validation. Let me know if you think it's good 😃

[coveralls]

Coverage increased (+0.4%) to 83.198% when pulling 7edc2d0 on bbonamin:ruby20 into 501d593 on shakacode:master.

[coveralls]

Coverage increased (+0.4%) to 83.198% when pulling 7edc2d0 on bbonamin:ruby20 into 501d593 on shakacode:master.

[coveralls]

Coverage increased (+0.4%) to 83.198% when pulling 7edc2d0 on bbonamin:ruby20 into 501d593 on shakacode:master.

[coveralls]

Coverage increased (+0.02%) to 82.775% when pulling 7edc2d0 on bbonamin:ruby20 into 501d593 on shakacode:master.

[justin808]

Please rebase your changes on top of my latest commit.

[bbonamin]

Done 👍 ! Merry Christmas! 🎄

[coveralls]

Coverage increased (+0.006%) to 99.292% when pulling ab689f0 on bbonamin:ruby20 into 8bcaa34 on shakacode:master.

[coveralls]

Coverage increased (+0.006%) to 99.292% when pulling ab689f0 on bbonamin:ruby20 into 8bcaa34 on shakacode:master.

[coveralls]

Coverage increased (+0.006%) to 99.292% when pulling ab689f0 on bbonamin:ruby20 into 8bcaa34 on shakacode:master.

[justin808]

Small suggestions @bbonamin.

Looking good!

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Reviewed 4 of 7 files at r1, 3 of 3 files at r2, 1 of 1 files at r3.
Review status: all files reviewed at latest revision, 2 unresolved discussions.

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app/helpers/react_on_rails_helper.rb, line 263 at r3 (raw file):

  def server_rendered_react_component_html(
    props, react_component_name, dom_id, prerender: required("prerender"),
    trace: required("trace"), raise_on_prerender_error: required("raise_on_prerender_error")

We should do these one per param per line. Easier to read.

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lib/react_on_rails/test_helper/webpack_assets_status_checker.rb, line 14 at r3 (raw file):

      def initialize(
        generated_assets_dir: raise(ArgumentError, "generated_assets_dir is required"),
        client_dir: raise(ArgumentError, "client_dir is required"),

can we use the helper required here?

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Comments from Reviewable

[justin808]

Review status: all files reviewed at latest revision, 3 unresolved discussions.

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CHANGELOG.md, line 9 at r3 (raw file):

*Please add entries here for your pull requests.*
##### Fixed
- Added support for Ruby 2.0.

Please see the other changelog entries and make consistent.

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Comments from Reviewable

[justin808]

Please put your changelog comments under 6.3.3.

[bbonamin]

@justin808 Thanks for the feedback! I've addressed your comments, and added a required_ruby_version to the gemspec (http://guides.rubygems.org/specification-reference/), so it's picked up by rubygems.org

[justin808]

GREAT JOB!

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Reviewed 5 of 5 files at r4.
Review status: all files reviewed at latest revision, 3 unresolved discussions.

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Comments from Reviewable

[coveralls]

Coverage increased (+0.008%) to 99.294% when pulling 14488d2 on bbonamin:ruby20 into ccd970a on shakacode:master.

[coveralls]

Coverage increased (+0.008%) to 99.294% when pulling 14488d2 on bbonamin:ruby20 into ccd970a on shakacode:master.

[coveralls]

Coverage increased (+0.008%) to 99.294% when pulling 14488d2 on bbonamin:ruby20 into ccd970a on shakacode:master.

[mapreal19]

Thanks @bbonamin!

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Reviewed 1 of 7 files at r1, 2 of 3 files at r2, 1 of 1 files at r3, 5 of 5 files at r4.
Review status: all files reviewed at latest revision, 3 unresolved discussions, some commit checks broke.

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Comments from Reviewable