Add comment formatting

[0x1mason]

This PR allows for util.format style comment formatting

[ljharb]

• just arguments.length is sufficient, no need to Object.keys (also that makes it require ES5, which this lib does not)
• It seems like this might be easier to just format.apply(null, arguments) in every case?

[0x1mason]

Calling format.apply in all cases changes the behavior, e.g. test.comment({answer:42}) will print {answer:42} whereas the current code prints [object Object]. I'm happy to make the change, as I think that's preferable behavior, but it's up to you.

[ljharb]

Ah, interesting. We definitely want to avoid breaking changes.

Either way, I think perhaps the ES3 equivalent of format.apply(null, Array.prototype.map.call(arguments, String)) might be the semantic we want here? What's the use case for supporting format's behavior with non-strings?

[0x1mason]

Use case would be, e.g., console.log-style debugging where you want to log object contents. With the change as it stands you can do t.cmt('%j', obj). Formatting everything, you could do t.cmt(obj).

Doesn't sound like 5 fewer characters is worth the risk of breaking older code tho.

[0x1mason]

@ljharb Pushed fixes.

[0x1mason]

@ljharb Added a comment to explain the conditional

[ljharb]

sadly I still don't think this is sufficient - previously, multiple arguments were ignored, and I still might have done arr.forEach(t.comment) for example, and relied on the stringification despite passing 3 arguments. I think that the first argument must never be stringified to avoid a breaking change.

[0x1mason]

Are you suggesting something like this?

if args[0] is a string and args.len > 1:
  expand the string
else:
  ignore

[0x1mason]

Also, what about a new function ,eg format, comments, etc

[ljharb]

No, I'm suggesting always stringifying the first argument no matter what, and not adding the ability to implicitly log object contents.

[ljharb]

This remains an issue - to restate, I think that we need something like format.apply(null, Array.prototype.map.call(arguments, String)) to ensure that everything is always stringified.

[ljharb]

This has been rebased.