ci: run against Ruby 3.4 (#3079)

* ci: run against Ruby 3.4

* fix: frozen string warning

Fixes warning `literal string will be frozen in the future`
in `faker/default/json.rb` by adding frozen-string literal pragma,
but creating a mutable string when needed by calling `#dup`.

Author: thdaraujo

.github/workflows/ruby.yml

@@ -24,7 +24,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.0'
+          ruby-version: '3.4'
 
       - name: Install dependencies
         run: bundle install
@@ -42,6 +42,7 @@ jobs:
           - '3.1'
           - '3.2'
           - '3.3'
+          - '3.4'
           - 'head'
           - truffleruby-head
     continue-on-error: ${{ endsWith(matrix.ruby, 'head') }}

.rubocop.yml

@@ -78,9 +78,6 @@ Style/FormatStringToken:
 
 Style/FrozenStringLiteralComment:
   Description: Add the frozen_string_literal comment to the top of files to help transition from Ruby 2.3.0 to Ruby 3.0.
-  Exclude:
-    - 'lib/faker/default/json.rb'
-    - 'test/faker/default/test_faker_json.rb'
 
 Style/For:
   Description: Checks use of for or each in multiline loops.

lib/faker/default/json.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Faker
   class Json < Base
     require 'json'
@@ -104,17 +106,20 @@ def add_hash_to_bottom(hash, key_array, width, options)
       end
 
       def add_hash(key_array, hash, width, options)
-        string_to_eval = 'hash'
+        string_to_eval = 'hash'.dup
+
         key_array.length.times do |index|
           string_to_eval << "['#{key_array[index]}']"
         end
         string_to_eval << " = #{build_shallow_hash(width, options)}"
         eval(string_to_eval)
+
         hash
       end
 
       def build_keys_from_array(key_array)
-        key_string = ''
+        key_string = ''.dup
+
         key_array.each do |value|
           key_string << "['#{value}']"
         end

test/faker/default/test_faker_json.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative '../../test_helper'
 
 class TestFakerJson < Test::Unit::TestCase