Restore UploadedFile compatibility with IO.copy_stream

In https://github.com/rails/rails/pull/28676 the `#to_path` method was
added to `ActionDispatch::Http::UploadedFile`. This broke usage with
`IO.copy_stream`:

  source = ActionDispatch::Http::UploadedFile.new(...)
  IO.copy_stream(source, destination)
  # ~> TypeError: can't convert ActionDispatch::Http::UploadedFile to IO (ActionDispatch::Http::UploadedFile#to_io gives Tempfile)

Normally `IO.copy_stream` just calls `#read` on the source object.
However, when `#to_path` is defined, `IO.copy_stream` calls `#to_io` in
order to retrieve the raw `File` object. In that case it trips up,
because `ActionDispatch::Http::UploadedFile#to_io` returned a `Tempfile`
object, which is not an `IO` subclass.

We fix this by having `#to_io` return an actual `File` object.

1 files changed, 4 insertions, 1 deletions

diff --git a/actionpack/lib/action_dispatch/http/upload.rb b/actionpack/lib/action_dispatch/http/upload.rb
index 827f022ca2..0da8f5c14e 100644
--- a/actionpack/lib/action_dispatch/http/upload.rb
+++ b/actionpack/lib/action_dispatch/http/upload.rb
@@ -20,7 +20,6 @@ module ActionDispatch
       # A +Tempfile+ object with the actual uploaded file. Note that some of
       # its interface is available directly.
       attr_accessor :tempfile
-      alias :to_io :tempfile
 
       # A string with the headers of the multipart request.
       attr_accessor :headers
@@ -84,6 +83,10 @@ module ActionDispatch
       def eof?
         @tempfile.eof?
       end
+
+      def to_io
+        @tempfile.to_io
+      end
     end
   end
 end