Add a `Contracts::Attrs` module containing attribute w/ contracts utilities.

[frewsxcv]

This pull request adds a new module Contracts::Attrs containing three methods to assist in using contracts with object attributes:

• attr_reader_with_contract <symbol>..., <contract>
  • Wraps attr_reader, validates contract upon 'getting'
• attr_writer_with_contract <symbol>..., <contract>
  • Wraps attr_writer, validates contract upon 'setting'
• attr_accessor_with_contract <symbol>..., <contract>
  • Wraps attr_accessor, validates contract upon 'getting' or 'setting'

[frewsxcv]

On a side note: thanks for making and maintaining contracts.ruby, it's an awesome project! 👌

[frewsxcv]

@egonSchiele Any thoughts about dropping support for Ruby 1.8? It's been EOL and hasn't received security updates for a few years, so to me it feels like a safe decision. If you're onboard with that, I can open a new PR for that and then rebase this on top of that.

[egonSchiele]

I like this 👍 I agree that we can drop support for Ruby 1.8.

[frewsxcv]

PR opened: https://github.com/egonSchiele/contracts.ruby/pull/256

[egonSchiele]

can you merge master into this branch? ci should pass, and then I'll merge

[frewsxcv]

Rebased.

[frewsxcv]

Is that error related to my change here? https://github.com/egonSchiele/contracts.ruby/commit/8e6d4eec01bc64bff50192a63ac236ee34449401#diff-eacde0c7f8149b55a880ae5fdcd84b3aL7

[egonSchiele]

Looks like the issue is, methods created using attr_* don't have a source_location, which makes sense since they are generated dynamically. This diff fixes ci:

diff --git a/lib/contracts/support.rb b/lib/contracts/support.rb
index 780455c..f3efa20 100644
--- a/lib/contracts/support.rb
+++ b/lib/contracts/support.rb
@@ -5,7 +5,11 @@ module Contracts
         return method.method_position if method.is_a?(MethodReference)

         file, line = method.source_location
-        file + ":" + line.to_s
+        if file.nil? || line.nil?
+          ""
+        else
+          file + ":" + line.to_s
+        end
       end

       def method_name(method)

I can merge this branch and fix.

[egonSchiele]

thank you!

[frewsxcv]

More inportantly, thanks for maintaining this great library :)