Need to escape ASCII control characters

[serde-rs]

Need to escape ASCII control characters

[dtolnay]

A PR would be appreciated!

[raphlinus]

I have a minimal patch for this, but it looks like #58 is a completely different approach to fixing it. If you still want the PR to escape_bytes lemme know and I'm happy to upload it.

[dtolnay]

Thanks but based on the discussion in #58 we plan to remove escape_bytes entirely (see #60). We are waiting to hear from @erickt regarding #58.

[raphlinus]

So, looking over the discussion, I have some concerns. As a user of serde-json, I would have a very negative reaction to anything that slowed down serialization. "You should use msgpack instead of json" is already one of the major pieces of feedback I get - I depend on serializing large blocks of text performantly. I'm also not a fan of escaping things not required by the spec. To me, "other json encoders do it" is not a good enough reason. Lastly, I'm not a fan of adding complexity to deal with unicode when it's not required.

So I uploaded #65, which is what I'd personally like to see. I'm also in favor of removing escape_bytes, as I agree that it doesn't make sense (it's impossible to safely serialize binary to json), but I didn't put that in my PR because it kinda seems like a separate issue. I'd be happy to update my PR if there's agreement.

Totally up to @erickt what he prefers, but I figured I would give him the option and present my reasoning behind it.

[PaulGrandperrin]

After my PR would have merged, I was about to propose to add an option to the serializer.
This option would have been about escaping or not non-ascii characters. It can be useful to generate ascii-compatible Jsons.
In Python, this option is called ensure_ascii.
To address @raphlinus needs, we could make this option tristate like this:

enum Escaping {
    Minimal, // according to ECMA-404
    AllControlCharacters, // plus DEL and C1 characters
    AllNonAscii, // everything above 127 (C1 characters are above 127)
}