Bug #13647: Some weird behaviour with keyword arguments

• Status: Closed
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -
• ruby -v: 2.3.0, 2.4.0
• Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN

[Arepo (Sasha Cooper)]

I was just playing around and found this weird behaviour, which seems to be in at least Ruby 2.3.0 and Ruby 2.4.0:

    hashie = Hashie::Mash.new(a: :b)

    def foo(hashie)
      hashie.inspect
    end

    def woo(hashie, bashie: nil)
      hashie.inspect
    end

    def zoo(hashie = nil, cashie: nil)
      hashie.inspect
    end

    foo(hashie)    # => "#<Hashie::Mash a=:b>"

    woo(hashie)    # => "#<Hashie::Mash a=:b>"

So far so good, but when we call the third method, we get this:

    zoo(hashie)    # => "{\"a\"=>:b}"

Similarly,

    zoo(:symbol)   # => ":symbol"

Is this intentional behaviour? If so, what's the rationale? If not, is it a known issue?

[Arepo (Sasha Cooper)]

• ruby -v set to 2.3.0, 2.4.0

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

I couldn't reproduce it with hashie-3.5.6, from 2.0.0 through trunk.

[nobu (Nobuyoshi Nakada)]

After the previous developers' meeting, Matz said an idea to restrict it to only T_HASH and not to call to_hash method, but it breaks mocks in rubyspec so much.

[nobu (Nobuyoshi Nakada)]

Just an idea to keep the original argument, if something left.

https://github.com/nobu/ruby/tree/bug/13647-non-hash-rest

[hsbt (Hiroshi SHIBATA)]

• Related to Feature #14183: "Real" keyword argument added

[marcandre (Marc-Andre Lafortune)]

• Status changed from Feedback to Open
• Assignee set to matz (Yukihiro Matsumoto)

nobu (Nobuyoshi Nakada) wrote:

Just an idea to keep the original argument, if something left.

https://github.com/nobu/ruby/tree/bug/13647-non-hash-rest

I agree that if the conversion of a hash-like argument to keyword parameter fails because the keys aren't all symbols, the original object should be passed.

I would do this without waiting for final decision on if to_hash is acceptable for keyword arguments or not, since even if it is decided to change so that to_hash isn't sufficient, the new behavior will be to receive the original object.

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Closed

In all released versions of Ruby I tested, zoo(hashie) raises ArgumentError.

With the changes in #14183, in the master branch, you also get a warning notifying you of the upcoming behavior change:

zoo(hashie)
# file.rb: warning: The last argument for `zoo' (defined at file.rb:14) is used as the keyword parameter
# file.rb:14:in `zoo': unknown keyword: :a (ArgumentError)

In Ruby 3, the behavior for zoo will be the same as foo and woo.