Avoid warnings in Ruby 3.1 when finalizer is called twice [fix #585]

CHANGELOG.md

@@ -1,6 +1,7 @@
 ##  Unreleased
 
 ### Changed/Added
+- Prevent warnings on Ruby 3.1 if finalizer is called twice [TODO](https://github.com/roo-rb/roo/pull/TODO)
 
 ##  [2.10.0] 2023-02-07
 

lib/roo/tempdir.rb

@@ -4,7 +4,10 @@ def finalize_tempdirs(object_id)
       if @tempdirs && (dirs_to_remove = @tempdirs[object_id])
         @tempdirs.delete(object_id)
         dirs_to_remove.each do |dir|
-          ::FileUtils.remove_entry(dir)
+          # Pass force=true to avoid an exception (and thus warnings in Ruby 3.1) if dir has
+          # already been removed. This can occur when the finalizer is called both in a forked
+          # child process and in the parent.
+          ::FileUtils.remove_entry(dir, true)
         end
       end
     end

test/helpers/test_accessing_files.rb

@@ -36,6 +36,27 @@ def test_finalize
     end
   end
 
+  def test_finalize_twice
+    skip if defined? JRUBY_VERSION
+
+    instance = Class.new { include Roo::Tempdir }.new
+
+    tempdir = instance.make_tempdir(instance, "my_temp_prefix", nil)
+    assert File.exist?(tempdir), "Expected #{tempdir} to initially exist"
+
+    pid = Process.fork do
+      # Inside the forked process finalize does not affect the parent process, but does delete the
+      # tempfile on disk
+      instance.finalize_tempdirs(instance.object_id)
+    end
+
+    Process.wait(pid)
+    refute File.exist?(tempdir), "Expected #{tempdir} to have been cleaned up by child process"
+
+    instance.finalize_tempdirs(instance.object_id)
+    refute File.exist?(tempdir), "Expected #{tempdir} to still have been cleaned up"
+  end
+
   def test_cleanup_on_error
     # NOTE: This test was occasionally failing because when it started running
     #       other tests would have already added folders to the temp directory,