(parser) Public API methods should validate input types better

[emanuelb]

Running hljs.highlightAuto(1)

Result:

Uncaught TypeError: value.replace is not a function
    at escapeHTML (/home/user/node_modules/highlight.js/lib/core.js:45:6)
    at justTextHighlightResult (/home/user/node_modules/highlight.js/lib/core.js:1763:14)
    at Object.highlightAuto (/home/user/node_modules/highlight.js/lib/core.js:1787:18)

it happend when I forget to use .toString() in below code on buffer:

var fs = require('fs');
var buffer = fs.readFileSync("file");
hljs.highlightAuto(buffer)

fix:
ensure code param is in correct type (string) otherwise return error (it's not string, type is X)

[joshgoebel]

We probably could do better here, but if someone was going to tackle this I'd want a PR that dealt with ALL the public API methods, not just the "issue of the day"... ie fix the whole problem (I've renamed the issue accordingly) I'd prefer not to add a ton of validation clutter to the codebase either - we have a lot of API public methods - I'd want to wrap this kind of thing up in some type of nice abstraction:

// just a rough idea
validateTypes("highlight", arguments,
      ["languageName", "code", "ignoreIllegals","continuation"],
      {
        languageName: "string", 
        code: "string", 
        ignoreIllegals: "boolean?", 
        continuation: "object?"
    })

This raises a few questions:

• Is there a nice JS type library we could pull in to do this for us - vs writing it from scratch?
• Would we even want to do that (use an external lib) since currently we are "zero requirements" and always have been...
• It would have to be a tiny library with no/minimal requirements itself even to be considered I think.
• Could we somehow do this at compile time using our existing TypeScript typing - is there tooling for that kind of thing?

I'm not opposed to this - if it's done nicely/properly - but we've also managed without it for forever, so I'd say it's not the highest priority IMHO. Leaving this open to continue the discussion.

[joshgoebel]

This work would pair well with #2277

[joshgoebel]

Periodic issue review. This type of feature is really not helpful once code is in production - and would only add bloat while providing zero or almost zero benefit. It would make some sense perhaps in a debug or development build - which isn't something we currently have. I'm not sure it's worth creating another build target (dev) just to add run-time type validation. Setting this to auto-close.