[ruby-core:116266] [Ruby master Feature#18576] Rename `ASCII-8BIT` encoding to `BINARY`

17 Jan 2024

      Issue #18576 has been updated by naruse (Yui NARUSE).

Even if you "fix" gems, the number of affected gems insists there are as many as private rails applications.
Such incompatibility is not acceptable.

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Feature #18576: Rename `ASCII-8BIT` encoding to `BINARY`
https://bugs.ruby-lang.org/issues/18576#change-106288

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Target version: 3.4
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### Context

I'm now used to it, but something that confused me for years was errors such as:

```ruby
...
...
"fée" + "\xFF".b
(irb):3:in `+': incompatible character encodings: UTF-8 and ASCII-8BIT (Encoding::CompatibilityError)

When you aren't that familiar with Ruby, it's really not evident that `ASCII-8BIT` basically means "no encoding" or "binary".

And even when you know it, if you don't read carefully it's very easily confused with `US-ASCII`.

The `Encoding::BINARY` alias is much more telling IMHO.

### Proposal

Since `Encoding::ASCII_8BIT` has been aliased as `Encoding::BINARY` for years, I think renaming it to `BINARY` and then making asking `ASCII_8BIT` the alias would significantly improve usability without backward compatibility concerns.

The only concern I could see would be the consistency with a handful of C API functions:

  - `rb_encoding *rb_ascii8bit_encoding(void)`
  - `int rb_ascii8bit_encindex(void)`
  - `VALUE rb_io_ascii8bit_binmode(VALUE io)`

But that's for much more advanced users, so I don't think it's much of a concern.

-- 
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