[ruby-core:68563] [Ruby trunk - Feature #10984] Hash#contain? to check whether hash contains other hash

Issue #10984 has been updated by Olivier Lacan.


Erik Michaels-Ober wrote:
> I agree that `#include?` is a more consistent and appropriate name for this method. I would prefer to see that change introduced in Ruby 3.0 than settle for this suboptimal change in Ruby 2.

From the many conversations I've had with folks after [publishing the original proposal for this](http://olivierlacan.com/posts/proposal-for-a-better-ruby-hash-include/) it seemed that my expectations for `Hash#include?`'s behavior didn't match many (if not most) people's expectations so it seemed unlikely that such a breaking change would ever be favored.

I don't think a brand new method would be such a bad idea in 2.3 because it would allow for a smoother upgrade path. People could start using `Hash#contain?` when 2.3 ships and then the internal implementation of `Hash#include?` could be swapped in 3.0 if that is deemed a good idea later on.

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Feature #10984: Hash#contain? to check whether hash contains other hash
https://bugs.ruby-lang.org/issues/10984#change-51878

* Author: Olivier Lacan
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
Comparing hashes seems like a common practice but there currently isn't a method to ask a 
hash instance whether it includes another hash instance.

The most intuitive method to reach for would be `Hash#include?` but it is in fact an alias to `Hash#has_key?`

What I'm looking for can be achieved with:

~~~
class Hash
  def contain?(other)
    self.merge(other) == self
  end
end
~~~

Here's a simple demo of `#contain?` in use:

~~~
{ a: true, b: false }.contain?({ a: true})
# => true

{ a: true, b: false }.contain?({ b: false})
# => true

{ a: true, b: false }.contain?({ a: false})
# => false

{ a: true, b: false }.contain?({ c: true})
# => false
~~~

One important note is that this method is *not checking for nested hash matches*.
This may need to be addressed when the parameters include a nested hash perhaps.

Thanks to Terence Lee's help, nobu created a patch for this feature last year. 
I've only modified the name of the method from [his original patch](https://gist.github.com/nobu/dfe8ba14a48fc949f2ed) and attached it to this issue.

---Files--------------------------------
Hash#contain_.patch (2.22 KB)


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