From: "YO4 (Yoshinao Muramatsu)" <noreply@...>
Date: 2022-12-09T16:02:15+00:00
Subject: [ruby-core:111247] [Ruby master Feature#19191] Implicit console input transcoding is more desirable

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

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

* Author: YO4 (Yoshinao Muramatsu)
* Status: Open
* Priority: Normal
----------------------------------------
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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