From: ozydingo@...
Date: 2016-03-08T02:26:19+00:00
Subject: [ruby-core:74214] [Ruby trunk Bug#10708] In a function call, double splat of an empty hash still calls the function with an argument

Issue #10708 has been updated by Andrew Schwartz.


Adding to this, the current behavior results in the following inconsistent behavior: I can call an argless method using a double-splatted empty Hash directly, but this cannot be done via a delegating method. I'm encountering this an an issue with subclasses that override argless parent methods with kwargs, and I would argue that the difference in behavior when calling bar directly vs calling it via foo is very surprising.

~~~ruby
def foo(*args, **kwargs)
  p args
  p kwargs
  bar(*args, **kwargs)
end

def bar
  puts "yay"
end
~~~

~~~
2.2.2 > bar
# => yay
2.2.2 > bar(*[], **{})
yay
2.2.2 > foo
[]
{}
ArgumentError: wrong number of arguments (1 for 0)
    from (irb):13:in `bar'
    from (irb):23:in `foo'
    from (irb):25
~~~

----------------------------------------
Bug #10708: In a function call, double splat of an empty hash still calls the function with an argument
https://bugs.ruby-lang.org/issues/10708#change-57350

* Author: Damien Robert
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* ruby -v: ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
Consider this:

~~~ruby
def foo; end
foo(*[]) #Splatting an empty list is ok
foo(**{}) #Double splatting an empty hash is like calling foo({}) which gives an error
~~~

This is annoying in a function that is a wrapper around another function and just process some keywords:

~~~ruby
def wrapper(*args, keyword: true, **others)
  puts keyword
  wrappee(*args,**others) #here this code will fail if others is empty
end
~~~




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