[ruby-core:107515] [Ruby master Feature#18576] Rename `ASCII-8BIT` encoding to `BINARY`

[duerst <noreply@ruby-lang.org>]

Issue #18576 has been updated by duerst (Martin Dürst).


Well, it's actually not just binary. Binary would mean that none of the bytes have any 'meaning' (i.e. characters) assigned to them. But ASCII-8BIT actually has character 'meaning' assigned to the ASCII range.
You can for example do the following:
```Ruby
u = (b = "abcde".force_encoding('ASCII-8BIT')).encode('UTF-8')
```
This gives you the string "abcde" with the encoding UTF-8. This shows that the lower 7 bits are interpreted the same as US-ASCII. The range with the 8th bit set, on the other hand, is just binary values, so
```Ruby
"\xCD".force_encoding('ASCII-8BIT').encode('UTF-8')
```
produces this error:
```
Encoding::UndefinedConversionError ("\xCD" from ASCII-8BIT to UTF-8)
```

I choose UTF-8 as the target encoding because that contains all of Unicode, so the error cannot be because the source character doesn't exist in the target encoding.

So there's indeed some complexity here, but it's not exactly what you think.


----------------------------------------
Feature #18576: Rename `ASCII-8BIT` encoding to `BINARY`
https://bugs.ruby-lang.org/issues/18576#change-96420

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
----------------------------------------
### 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.




-- 
https://bugs.ruby-lang.org/