From: "YO4 (Yoshinao Muramatsu) via ruby-core" <ruby-core@...>
Date: 2024-11-22T14:47:34+00:00
Subject: [ruby-core:119994] [Ruby master Feature#19191] Implicit console input transcoding is more desirable

Issue #19191 has been updated by YO4 (Yoshinao Muramatsu).


irb changes $stdin.{external,internal}_encoding.
This causes gets() to no longer return the correct content in irb.

```
C:\>chcp
������������������ ���������: 932

C:\>ruby -e "p [STDIN.external_encoding, STDIN.internal_encoding]"
[#<Encoding:Windows-31J>, #<Encoding:UTF-8>]

C:\>ruby -e "gets.then { p [_1, _1.encoding] }"
���
["���\n", #<Encoding:UTF-8>]

C:\>irb
irb(main):001> p [STDIN.external_encoding, STDIN.internal_encoding];
[#<Encoding:UTF-8>, nil]
irb(main):002> gets.then { p [_1, _1.encoding] };
���
["\x82\xA0\n", #<Encoding:UTF-8>]
irb(main):003>
```

It seems that making changes on the irb side would have a negative impact on test, etc.
I think it is more reliable to deal with this on the ruby.exe side.

----------------------------------------
Feature #19191: Implicit console input transcoding is more desirable
https://bugs.ruby-lang.org/issues/19191#change-110735

* Author: YO4 (Yoshinao Muramatsu)
* Status: Open
----------------------------------------
In response to Bug #18353, STDIN.internal_encoding are set and encoding is converted explcitly on Windows platform.
For example, ```[STDIN.external_encoding, STDIN.internal_encoding] # => [Encoding::Windows-31J, Encoding::UTF-8]``` if STDIN is console.

I feel that internal_encoding should be reserved for specific applications. And I think setting internal_encoding to STDIN is not foreseened.

Today I found irb breaks STDIN encoding, like

```
>ruby -rirb -e "p [$stdin.external_encoding, $stdin.internal_encoding]; IRB.setup(''); IRB::Irb.new(); p [$stdin.external_encoding, $stdin.internal_encoding]"
[#<Encoding:Windows-31J>, #<Encoding:UTF-8>]
[#<Encoding:UTF-8>, nil]
```

We know input has console code page encoding. So we always can convert encoding from console code page to io_input_encoding().

### proposal
when reading from console on Windows, input encoding is enfoced to console code page and encoding conversion is implicitly applied.

when ```set_encoding("UTF-8")``` implicitly converts console code page to UTF-8.
when ```set_encoding("CP437", "UTF-8")``` implicitly converts console code page to UTF-8. external_encoding is ignored.

binmode or binary input method is not affected by these specifications.
set_encoding, etc. will continue to work as before, and this specification will affect only when encoding conversion on read (NEED_READCONV() and make_readconv()).




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