CSV::Row#each etc. return enumerator when no block given

In Ruby 2.3, These methods do not return enumerator when no block is given.

CSV::Row.new(%w(banana mango), [1,2]).each #=> #<CSV::Row "banana":1 "mango":2>

CSV::Row.new(%w(banana mango), [1,2]).delete_if #=> #<CSV::Row "banana":1 "mango":2>

Some methods raise exception because of this behavior.

> ruby -rcsv -e 'CSV::Table.new([CSV::Row.new(%w{banana mango}, [1, 2])]).by_col.each'
 #=> /Users/sushant/.rbenv/versions/2.3.0/lib/ruby/2.3.0/csv.rb:850:in `block in each': undefined method `[]' for nil:NilClass (NoMethodError)
  from /Users/sushant/.rbenv/versions/2.3.0/lib/ruby/2.3.0/csv.rb:850:in `each'
  from /Users/sushant/.rbenv/versions/2.3.0/lib/ruby/2.3.0/csv.rb:850:in `each'
  from -e:1:in `<main>'

Ruby 2.4 fixed this issue.

CSV::Row.new(%w(banana mango), [1,2]).each #=> #<Enumerator: #<CSV::Row "banana":1 "mango":2>:each>

CSV::Row.new(%w(banana mango), [1,2]).delete_if #=> #<Enumerator: #<CSV::Row "banana":1 "mango":2>:delete_if>

As we can see, these methods now return an enumerator when no block is given.

In Ruby 2.4 following code will not raise any exception.

> ruby -rcsv -e 'CSV::Table.new([CSV::Row.new(%w{banana mango}, [1, 2])]).by_col.each'