add ruby 2.2, 2.3, and 2.4 to CI matrix

.github/workflows/development.yml

@@ -14,6 +14,9 @@ jobs:
           - macos
 
         ruby:
+          - 2.2
+          - 2.3
+          - 2.4
           - 2.5
           - 2.6
           - 2.7

Gemfile

@@ -26,14 +26,16 @@ group :test do
   gem 'rspec', '~> 3.3'
 end
 
+RUBY_VERSION_FLOAT = RUBY_VERSION[/\d+\.\d+/].to_f
+
 group :development do
   gem 'bundler'
   gem 'gems', require: false
   gem 'guard-rspec', require: false
-  gem 'guard-rubocop'
+  gem 'guard-rubocop' unless RUBY_VERSION_FLOAT < 2.4
   gem 'netrc', require: false
   gem 'octokit', require: false
   gem 'pry-rescue'
-  gem 'rubocop', '0.91.0'
+  gem 'rubocop', '0.91.0' unless RUBY_VERSION_FLOAT < 2.4
   gem 'yard', require: false
 end

lib/listen/adapter/base.rb

@@ -88,7 +88,7 @@ def stop
       private
 
       def _stop
-        @run_thread&.kill
+        @run_thread && @run_thread.kill
         @run_thread = nil
       end
 

lib/listen/adapter/darwin.rb

@@ -69,7 +69,7 @@ def _process_event(dir, path)
       end
 
       def _stop
-        @worker_thread&.kill
+        @worker_thread && @worker_thread.kill
         super
       end
     end

lib/listen/adapter/linux.rb

@@ -102,7 +102,7 @@ def _dir_event?(event)
       end
 
       def _stop
-        @worker&.close
+        @worker && @worker.close
 
         super
       end

lib/listen/event/config.rb

@@ -25,7 +25,7 @@ def sleep(seconds)
       end
 
       def call(*args)
-        @block&.call(*args)
+        @block && @block.call(*args)
       end
 
       def callable?

lib/listen/event/loop.rb

@@ -29,7 +29,7 @@ def initialize(config)
       end
 
       def wakeup_on_event
-        if started? && @wait_thread&.alive?
+        if started? && @wait_thread && @wait_thread.alive?
           _wakeup(:event)
         end
       end
@@ -67,7 +67,7 @@ def pause
       def stop
         transition! :stopped
 
-        @wait_thread&.join
+        @wait_thread && @wait_thread.join
         @wait_thread = nil
       end