Implement a more strict hostname validation (isValid)

[remusao]

Attempt at addressing #59 and #73 (it should be trivial to allow _ as well, but we should probably discuss of a possible API for that there => #99).

This function implements a more strict validation of the hostnames. It checks:

• maximum total size (255)
• maximum size of a label (63)
• allowed characters: [0-9a-zA-Z] for first character and [0-9a-zA-Z-] for the rest
• Forbid two consecutive dots

As far as I know that should be it, but let me know if you see some corner cases that are not covered.

Regarding performance, this one times at:

tldjs#isValid x 8,112,000 ops/sec ±0.26% (96 runs sampled)

This is about x6 slower than the previous implementation (which did not check much). So I'd say it's still fast enough (compared to cleanHost ~ 360,000 ops/sec or getDomain ~ 120,000 ops/sec). I also compared it with a more naive validation regex (which does not check every thing) which times at 9,574,128 ops/sec.[1]

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[1] /^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$/ (does not check maximum size, maximum label size, forbid trailing dot).

[remusao]

I changed the regex to also check the size of the labels, and it becomes slower than the implementation of this PR. (for the record)

Also, not sure what's happening with the failing tests. I could not yet reproduce locally.

[remusao]

The latest implementation handles a few more corner cases and is faster:

tldjs#isValid x 10,525,000 ops/sec ±0.40% (94 runs sampled)

[remusao]

@oncletom Actually, I was wondering if we could add this check in the cleanHostValue, before doing anything, to check if the argument value is already a valid hostname. If not, we try to extract one. What do you think?

[thom4parisot]

Thanks @remusao, excellent work as usual 😄

I agree with the cleanHostValue integration — it would fail sooner and would prevent to clean something which does not have to be cleaned 👍

[remusao]

@oncletom We might want to close this one in favor of #103. What do you think? I also implemented the validation there + integration with cleanHostValue and a few other changes.

[thom4parisot]

Agreed 👍