Regression in CI benchmark

[curbengh]

Usually cold processing can complete within 25 seconds, lately I noticed it has increased to more than a minute.

I haven't find the cause yet, I did notice the regression in #3808 #3812 #3813

Commit Time (GMT)	Commit	Cold Processing Time (Node 8)
#3813
27 Oct 14:48	c8fee53	24s
29 Oct 12:26	330d88b	38s
#3808
28 Oct 06:39	28949da	23s
02 Nov 03:29	48d2c52	40s
#3812
27 Oct 13:32	3222513	23s
28 Oct 05:09	ab23935	35s

Reverting #3808 and #3813 in #3831, but no difference. Haven't try #3812 yet.

Commit Time (GMT)	Commit	PR	Cold Processing Time (Node 8)
Latest master
05 Nov 01:32	77f3e21	#3829	42s
Revert attempt
05 Nov 02:21	8a475a8	#3831	40s

---

I also tried dropping recent commits until 3448a6d, see revert-lodash tree. The processing time did come back to normal 26s (build log).

---

Looks like whatwg API is the cause #3812
I revert #3812 in #3834, processing time is 27s (build log).

In Node 13, it dropped from 81s to 27s.

[SukkaW]

	Node.js 8	Node.js 10	Node.js 12	Node.js 13
Current master branch (#3829)	37s	33s	85s	83s
PR #3834	27s	27s	27s	26s
PR #3835	41s	33s	85s	82s

@curbengh

I have to say, the benchmark result is consistent. The problem must be at whatwg URL api.

[SukkaW]

@curbengh

I have setup a benchmark on runkit: https://runkit.com/sukkaw/5dc278520410ce00133cb012

It seems that whatwg url is definitely slower.

[curbengh]

I just had an idea, since external_link filter incurs perf cost (regardless of legacy or whatwg), an alternative approach is to implement it under hexo-renderer-marked and hexo-renderer-markdown-it. This approach is more efficient because it is specific to links, compared to a filter that has to run through every content to look for links.

Having it under renderer means links in post/page can be applied, as long they are in []() markdown syntax. This means a limitation of renderer approach is that raw <a> (especially in theme layout) won't be applied. Another way to look at it is that the coverage is between external_link.field: post and external_link.field: site.

I still think external_link filter can be useful (especially the coverage offered by field: site), but disable it by default and enable it in renderer instead. Not now, perhaps in the next major version.

I intend to add the feature to hexo-renderer-marked in the coming days. It will be disabled by default.

[SukkaW]

@curbengh

I agree with that idea. We might add this to our Roadmap.

[curbengh]

Discussion move to #3846.