From: Run Paint Run Run <redmine@...>
Date: 2010-06-18T09:18:39+09:00
Subject: [ruby-core:30803] [Feature #3450] Format Strings with Named Arguments & Hash#default

Feature #3450: Format Strings with Named Arguments & Hash#default
http://redmine.ruby-lang.org/issues/show/3450

Author: Run Paint Run Run
Status: Open, Priority: Low
Category: core, Target version: 1.9.x

Is it intentional that the, undocumented, feature #442 (named arguments in format strings) ignores the Hash's default value? 

  >> hash = {greeting: 'Hello'}.tap{|h| h.default = 'World'}
  >> '%{greeting}, %{greeted}' % hash
  #=> KeyError: key{greeted} not found

It's quite common for templates to use default values. In interface localisation, untranslated strings may need to be substituted for the equivalent in the native language, or replaced with a generic string in the target language. When building reports with format strings, a default value of an empty string allows unexpanded format sequences to be non-fatal. In both cases, a default proc would provide even further flexibility.

Another perspective is that this behavior unnecessarily breaks the abstraction that default values are just like any other.


----------------------------------------
http://redmine.ruby-lang.org