Lint/FormatParameterMismatch false positive for fields with absolute argument numbers

[ghost]

In the format string for Kernel#format you can specify the absolute argument number before a field using (digit)$ flag. Here are examples from the docs:

sprintf("%1$*2$s %2$d %1$s", "hello", 8)   #=> "   hello 8 hello"
sprintf("%1$*2$s %2$d", "hello", -8)       #=> "hello    -8"

RuboCop currently fails to deal with such situations.

---

Expected behavior

No offenses.

Actual behavior

Lint/FormatParameterMismatch offense.

Steps to reproduce the problem

Given this minimal example:

# format.rb
format('%1$s %1$s', 'foo')

Run:

$ rubocop format.rb
Inspecting 1 file
W

Offenses:

format.rb:1:1: W: Lint/FormatParameterMismatch: Number of arguments (1) to format doesn't match the number of fields (0).
format('%1$s %1$s', 'foo')
^^^^^^

1 file inspected, 1 offense detected

RuboCop version

$ rubocop -V
0.60.0 (using Parser 2.5.3.0, running on ruby 2.5.1 x86_64-openbsd)

[koic]

Thanks for the feedback. I confirmed this reproduction and I opened a PR #6483.

[ghost]

Whoa, that's fast! Thank you.