Rubocop: why not using interpolation in Style::FormatString

[Ana06]

Currently Style/FormatString cop will complain about things like:

key = '%s/%s' % [dproject, dp.name]

and the autocorrect will change it by:

key = format('%s/%s', dproject, dp.name)

I wonder why not changing it by (using interpolation):

key = "#{dproject}/#{dp.name}"

I find it way more readable. Not sure if can be always be used. :thinking:

RuboCop version

$ rubocop -V
0.49.1 (using Parser 2.4.0.0, running on ruby 2.4.1 x86_64-linux-gnu)

[Drenmi]

They are not directly interchangeable. 🙂 Kernel#format does a lot more. It can pad strings, convert between types, and format numbers, depending on which references you use in the template.

There is a way to make it a bit more readable, and we've discussed adding a cop for it. You can name the references like so:

format("%<foo>s %<bar>s!", foo: "Hello", bar: "world")
#=> "Hello world!"

This cop isn't implemented yet, however.

[mikegee]

I was thinking the particular case presented here might be nice to handle: format strings containing only %s references could be replaced with interpolation. Yet another cop, or maybe not worth it 🤔

[Ana06]

@mikegee

format strings containing only %s references could be replaced with interpolation

Another cop would be great! Documenting that string interpolation is prefer in this case in Style::FormatString would also be a good idea :+1:

[backus]

There is a way to make it a bit more readable, and we've discussed adding a cop for it. You can name the references like so

Are you referring to something besides what Style/FormatStringToken does?

[Drenmi]

@backus: Ah! I remember this being mentioned, but didn't realize it was actually added. 😍

[ryanhageman]

Is this still an issue?