Bug #20418: `StringIO#read(..., buffer)` doesn't preserve buffer's encoding

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 3.2.2
• Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

[andrykonchin (Andrew Konchin)]

IO#read (and similar methods #read_nonblock, #readpartial, #sysread) when called with a buffer argument preserve its encoding. But StringIO#read doesn't do so:

file = File.open('test.rb')
buffer = "".encode(Encoding::ISO_8859_1)
file.read(10, buffer)
buffer.encoding # => #<Encoding:ISO-8859-1>

require 'stringio'
io = StringIO.new("# encoding")
buffer = "".encode(Encoding::ISO_8859_1)
io.read(10, buffer)
buffer.encoding # => #<Encoding:ASCII-8BIT>

I would expect StringIO's read and similar methods to preserve a buffer's encoding.

[byroot (Jean Boussier)]

Seems legit to me. Proposed patch: https://github.com/ruby/stringio/pull/95

• Status changed from Open to Closed

Applied in changeset git|75154dec73e1329693866e3a88cb9febb7635417.

---

[ruby/stringio] strio_read: preserve buffer encoding on partial
reads
(https://github.com/ruby/stringio/pull/95)

[Bug #20418]

Ruby IO#read preserves the encoding on partial read, but change it when
reading the whole IO

from commit https://github.com/ruby/ruby/commit/0ca7036682da:

• io.c (read_all): should associate default external encoding.
• io.c (io_read): should NOT associate default external encoding.

https://github.com/ruby/stringio/commit/073172da31

Co-authored-by: Jean Boussier [e-mail]