Fix broken Hashie::Hash#to_hash

[mhuggins]

Per my comment on the original pull request for this feature:

I'm running into an issue with this code. I'm trying to take a basic hash with string keys and convert it to a basic hash with symbol keys. Take the following example.

hash = {"id": 1, "name": "Bob"}
hash = Hashie::Hash[hash].to_hash(symbolize_keys: true)

This throws an exception in Hashie's to_hash method using the code provided here. The reason is that on line 15 the value of k is being changed from "id" or "name" to :id or :name respectively. Then on line 17, the call to self[k] returns nil since hash[:id] is not defined (only hash["id"] is defined), which then errors when trying to evaluate nil.each.

I think a proper fix would be to assign the key to a NEW variable instead. e.g.:

assignment_key = options[:symbolize_keys] ? k.to_sym : k.to_s
out[assignment_key] ||= []
self[k].each do |array_object|
  out[assignment_key] << (Hash === array_object ? array_object.to_hash : array_object)
end

Additionally, this fixes a similar issue even when :symbolize_keys is false (or not provided) to the #to_hash function. If a key is not already a string, then a similar error will be raised. There was not a test to cover this, so I added one.

[mhuggins]

If the two tests I added to this PR are run on master right now, both will fail. Try for yourself. :)

[dblock]

This has been merged, sorry for the delay. Thanks for contributing!

[mhuggins]

No problem, thanks so much! 😄