Issue #15927 has been updated by ashmaroli (Ashwin Maroli).


> Can you give us some actual use case(s) where such rewriting would not be possible, or very tedious?

One use-case would be where the Data used by `sprintf` is generated at runtime:
```ruby
require 'yaml'

# contents of 'path/to/config.yml':
#
# ---
# title: Hello World
# author: John Doe
# url: "https://www.example.com/blog"
#

config = YAML.load_file('path/to/config.yml')
# config == {"title"=>"Hello World", "author"=>"John Doe", "url"=>"https://www.example.com/blog"}

# This will fail. The alternative would be to convert the string keys to symbols beforehand.
"title = %{title}" % config
[...]
```

----------------------------------------
Feature #15927: Allow string keys to be used for String#% and sprintf methods
https://bugs.ruby-lang.org/issues/15927#change-78615

* Author: luke-gru (Luke Gruber)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Right now, in the methods sprintf() and String#%, only symbol keys can be used for named interpolation. For example (from the example documentation):

"foo = %{foo}" % { :foo => 'bar' }        #=> "foo = bar"

String keys do not work like this:

"foo = %{foo}" % { 'foo' => 'bar' }        #=> raises KeyError

I think string keys should work just the same as symbol keys here.

I've created a PR on github for this, perhaps misguidedly, but if can be found here: https://github.com/ruby/ruby/pull/2238

My argument for this feature is that String#gsub() and family works with string keys if given a Hash, for example:

"chocolate ice cream".gsub(/\bc/, { 'c' => 'C' }) #=> 'Chocolate ice Cream'

Also, I don't like having to symbolize keys in strings unnecessarily, but maybe that just goes back to when
Ruby couldn't GC some symbols.





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