IO.copy_stream keep pos of destination to beginning of file

[HoneyryderChuck]

This is the minimum repro I could make:

require "stringio"
require "tempfile"
a = StringIO.new
a << ("a"*100000)
b = Tempfile.new("test", encoding: Encoding::BINARY, mode: File::RDWR)
a.rewind
IO.copy_stream(a, b)
puts b.pos

Using ruby 3.2, the output is 100000, whereas in truffleruby, output is 0.

version was truffleruby 22.3.1, like ruby 3.0.3, GraalVM CE Native [x86_64-linux] (I use truffleruby for tests in docker, there is no v23 image available yet).

[eregon]

Thank you for the report.
This bug is due to

truffleruby/src/main/ruby/truffleruby/core/io.rb

Lines 368 to 370 in c6e6162

	elsif obj.respond_to? :to_path
	path = Truffle::Type.coerce_to obj, String, :to_path
	io = File.open path, mode

A Tempfile is not an IO or a File, it's a separate class using delegation:

irb(main):006:0> Tempfile.ancestors
=> [Tempfile, #<Class:0x00007f9b2de25e80>, Delegator, #<Module:0x00007f9b2de0a338>, BasicObject]

And so the coercion tries to_path which does exist on on Tempfile and Delegates to File#to_path, and therefore it creates another IO object.
I will check what's the actual logic in CRuby, maybe we shouldn't try to_path there or maybe there is a special case for Tempfile.

[eregon]

https://github.com/ruby/ruby/blob/2d6067dc7d02c5942da6636bba8b1629065aecf0/io.c#L13160 is the conversion logic in CRuby.
So it check if dst is ARGF or is not (an IO or a String or a #to_path), then dst_fptr = NULL.
And if that doesn't hold (Tempfile has to_path) then it tries rb_io_check_io which is #to_io first, then if not an IO tries FilePathValue (#to_path) and otherwise uses it as-is as an IO.

[eregon]

Fix in #3282

[HoneyryderChuck]

Thx for the prompt fix @eregon 🙏

Unrelated, but when can one expect docker truffleruby images targeting v23?

[eregon]

@HoneyryderChuck The Docker images for 23.0 and 23.1 are already available: https://github.com/graalvm/container/blob/master/truffleruby-community/README.md

[HoneyryderChuck]

Oh, i was still using ghcr.io/graalvm/truffleruby:latest, didn't know about the change. will upate CI builds accoringly, thx!

[eregon]

This fix will be in the 23.1.2 release which will be available on January 23, 2024.