Bug #15849: Using hash as first positional argument, mixed with named arguments causes unexpected behavior

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.4.5p335 (2018-10-18 revision 65137) [x86_64-linux]
• Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN

[jsmartt (Jared Smartt)]

If the first argument of a method defaults to an empty hash, and there is another keyword argument after it, it does not set first parameter given to the first argument

For example:

data = {}
# This method does not modify the data hash as expected
def add_to_data(data = {}, key: 'a')
  data[key] = 'value'
end
add_to_data(data)
puts data   # {}

Trying the following produces an error:

data = { b: 'val' }
add_to_data(data)   # ERROR: unknown keyword: b (ArgumentError)

There are a lot of other similar combinations of this method definition that do work as expected. It appears that having a default value for that first positional argument is what causes issues; see the attached script.

[jeremyevans0 (Jeremy Evans)]

I believe this is the same issue as #12717. We are trying to address this issue in #14183.

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed

I believe Jeremy :) and if it is not the same issue, please reopen it.