More BBCode parsers?

Yeah! I needed something highly extensible, flexible, and specifically WITH scoping rules so it always produces correct HTML. For instance, there's stuff like:

[b]This is bold! [i]AND ITALIC?[/b] oops where's [/i]?

Where you have unmatching closing tags. While a simple regex replacement may handle this any number of ways, this library will produce:

<b>This is bold! <i>AND ITALIC?</i></b> oops where&#x27;s ?

Another example:

And so [s] I'm just like [s] opening tons of [sup] tags? Maybe I'll close this [/s] one

And so <s> I&#x27;m just like <s> opening tons of <sup> tags? Maybe I&#x27;ll close this </sup></s> one</s>

All unclosed tags are automatically closed in the correct order, including any that were left at the end of the text. Unmatched closing tags are removed. Of course, this may not be what you want, but I've found that most older or established bbcode parsers work this way. With this library, you can feel (generally) safe knowing it will produce proper HTML.

With scoping rules, you also get access to tags which can reject other tags inside of them, by specifying the only vector (more later). For instance, in the extended tagset, I have [code] which rejects all types of matches except normal text and "garbage" (characters we throw away, like \r).

Quickstart

let bbcode = BBCode::default().unwrap(); // Or catch error
let html = bbcode.parse("[url]https://github.com[/url]")
// Make sure to reuse the BBCode you created! Creating is expensive!

Or, if you want the extended set (see next section for list):

// These are just vectors, which means you can construct your own!
let mut matchers = BBCode::basics().unwrap();
let mut extras = BBCode::extras().unwrap();
matchers.append(&mut extras);

//Note: this step could be expensive, as it has to compile a couple dozen regexes
let bbcode = BBCode::from_matchers(matchers);

// Cheap copy: they share the same pre-compiled regex, share it around!
let bbcode2 = bbcode.clone();

Or, if you want to add your own tag:

let mut matchers = BBCode::basics().unwrap();

// How your tag gets turned into HTML; you are given the open tag regex capture, the 
// pre-parsed pre-escaped body, and the closing tag regex capture (if the user provided it)
let emitter = |open_capture,body,_c| {
  //NOTE: in production code, don't `unwrap` the named capture group, it might not exist!
  let color = open_capture.unwrap().name("attr").unwrap().as_str();
  format!(r#"<span style="color:{}">{}</span>"#, color, body)
};

BBCode::add_tagmatcher(&mut matchers, "color", ScopeInfo::basic(Arc::new(emitter)), None, None)?;

let bbcode = BBCode::from_matchers(matchers);

The BBCode::add_tagmatcher method constructs a bbcode tag parser for you, but you can technically construct your own matcher manually which can match almost anything. For now, if you're just trying to add basic bbcode tags, you'll see in the above:

• First parameter is the list to append the matcher to (it adds multiple items).
• Second is the name of the bbcode tag, all lowercase (so this would match [color])
• Third is a special "ScopeInfo" struct, but we're calling the "basic" constructor and simply passing a boxed closure rather than configuring the entire ScopeInfo.
• That boxed closure is a so-called EmitScope, which gives you the regex capture for the open tag, the pre-html-escaped, pre-parsed body, and the closing tag regex capture, which you can use to output (emit) the constructed html. Note that, although the opening tag is nearly always given, the closing tag is OFTEN not given, especially if the user did not close their tags. Do not rely on the last parameter (_c in the example) existing
• Note that the opening tag capture has a named group called attr, which is the value of the attribute given in the bbcode tag. For instance, if you had [url=http://whatever]abc[/url], the match attr would house the string http://whatever (NOT pre-escaped, be careful!)
• The last two parameters are optional newline consumption before and after the opening and closing tag. For instance, if you wanted to consume the first newline before the opening tag, and the first newline after the closing tag, those two might look like Some((1,0)), Some((0,1)) (this may change in the future)

Rocket Web example

There are many web frameworks to choose from for rust, so having an example for each would be a bit difficult. Someone suggested Rocket, so here's an example in 0.5.0_rc2:

#[macro_use] extern crate rocket;
use rocket::response::content;
use bbscope::BBCode;

#[launch]
fn rocket() -> _ {
    let bbcode = BBCode::default();
    rocket::build()
      .mount("/", routes![ index ])
      .manage(bbcode) //Add as state, you want to reuse the bbcode object!!
}

#[get("/")]
fn index(bbcode: &State<BBCode>) -> content::RawHtml<String> {
  content::RawHtml(String::from(bbcode.parse("Hey, it's [b]bbcode[/b]! [i]Oops, [u]forgot to close[/i] a tag")))
}

Default supported tags:

BBCode is so varied, there's so many crazy tags and systems and nobody was ever able to agree on any, or at least if they did, it was too late. These are the tags supported in the 'basic' set:

• [b]bold[/b]
• [i]italic[/i]
• [s]strikethrough[/s]
• [u]underline[/u]
• [sup]superscript[/sup]
• [sub]subscript[/sub]
• [url=link*]url[/url] (=link attribute optional)
• [img=link*]link[/img] (only one needed: attribute or inner)
• [list][*]item[*]item2[/list]

Some of those may be nonstandard, and you may be missing some you find standard! If so, there's also an optional extended list:

• [quote=cite*]a blockquote[/quote] (=cite attribute optional)
• [code]verbatim pre[/code]
• [icode]verbatim inline[/icode]
• [youtube]youtube link*[/youtube] (CURRENTLY RENDERS AS LINK!)
• [h1]big header[/h1]
• [h2]medium header[/h2]
• [h3]small header[/h3]
• [anchor=name]some text linkable with #name[/anchor]
• [spoiler=name]some text to hide[/spoiler]

And of course, the usual HTML characters are escaped everywhere: ', ", &, <, >

URLs not inside a url or img tag are auto-linked, or at least a best attempt is made at autolinking them (your mileage may vary)

Caveats:

• Output removes \r but RETAINS \n rather than replacing with <br>. This was how an old bbcode parser I was using worked, and this was written to replace that. If there's a need, I can add modes for \n vs <br>
• Performance was not a main concern, although you can enable additional performance features with the perf feature (enables some regex optimizations, about a 4x improvement in my testing)
• Many rules are arbitrary and meant to copy an existing bbcode parser I used for many years

Changelog:

• 0.0.6: Small bugfix for conditional compilation
• 0.1.0: Full rewrite; if using BBCode::default(), or BBCode::basics() and BBCode::extras(), it should still compatible, but if you were creating custom tags at all, the entire system was scrapped in favor of the ScopeInfo and EmitScope combo
• 0.1.1: Small bugfix to enforce Sync + Send on closures (so bbcode can be used across threads)
• 0.1.2: Added class to "code" segments
• 0.1.3: Added ability to convert a bbcode parser into one that only consumes the scoped tags it had
• 0.1.4: Added secondary syntax I've seen around: [tag tag=attribute]

Future

I mostly published this for my own projects, which have specific requirements, but if for some reason this gets picked up and used and there are gaps or bugs or other required features, I'd be willing to work on it! I just don't see that happening lol