[ruby-core:54445] [ruby-trunk - Bug #8289][Open] [].join.encoding # => US-ASCII (I expect also UTF-8

Issue #8289 has been reported by peter_v (Peter Vandenabeele).

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Bug #8289: [].join.encoding # =>  US-ASCII  (I expect also UTF-8
https://bugs.ruby-lang.org/issues/8289

Author: peter_v (Peter Vandenabeele)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 
ruby -v: ruby 2.1.0dev (2013-04-19) [x86_64-darwin12.3.0]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


May be related to http://bugs.ruby-lang.org/issues/5379

$ date
Thu Apr 18 23:56:54 CEST 2013

$ rvm get stable

$ rvm install ruby-head
... long compile process ...

$ rvm use ruby-head
Using /Users/peter_v/.rvm/gems/ruby-head

$ ruby -v
ruby 2.1.0dev (2013-04-19) [x86_64-darwin12.3.0]

$ cat empty_array_join_returns_ASCII_encoding.rb 
puts ["abc"].join.encoding
puts [].join.encoding
puts [].join.encode("utf-8").encoding

# Actual result:

$ ruby -v empty_array_join_returns_ASCII_encoding.rb 
ruby 2.1.0dev (2013-04-19) [x86_64-darwin12.3.0]
UTF-8
US-ASCII
UTF-8

# Expected result

$ ruby -v empty_array_join_returns_ASCII_encoding.rb 
ruby 2.1.0dev (2013-04-19) [x86_64-darwin12.3.0]
UTF-8
UTF-8  # This is edited for expected result (not the actual result)
UTF-8

I would expect that in Ruby 2.0 with UTF-8 as default encoding,
the returned encoding of an array (with default encoding strings),
is _always_ UTF-8, independent of the size of the array.

The current behaviour breaks my tests for an output encoding of
UTF-8 in the case the array is empty.

My work around is  `array.join().encode("utf-8")` which works, but is ugly.


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