test/refactor: update isExternalLink

[SukkaW]

What does it do?

Try to fix #3833

#3833 (comment)

Screenshots

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[coveralls]

Coverage increased (+0.004%) to 97.148% when pulling 20d4ae4 on SukkaW:test_external_link_perf into a088ede on hexojs:master.

[SukkaW]

After 60acb95 , I managed to lower the generation duration from 86s to 76s on Node.js 12 & 13.

After 6d9ed7a , it drops from 76s to 72s on Node.js 13 (and Node.js 12 remains 76s).

[SukkaW]

From jsdelivr/bootstrapcdn#1391 , the matainer of bootstrapcdn said the url.parse is faster. Maybe we should have a benchmark on which one is faster.

[SukkaW]

According to the benchmark, the current "safe whatwg url" or urlObj is 2x slower than pure new URL, 6x slower than url.parse().

Since whatwg url is required in isExternalLink to ignore mailto: and so on, I might pass sitehost as base in new URL to avoid urlObj.

[SukkaW]

The generation duration is dropped to:

• Node.js 10: 27s
• Node.js 12: 26s
• Node.js 13: 24s

[SukkaW]

@curbengh

It is now ready for review.

After this PR is approved, we should close this PR and update isExternalLink in hexo-util.

Although url.parse() is deprecated, since it is only deprecated in documents, and it is much faster and cleaner than whatwg url, we should use it when necessary. #3812 uses whatwg url only for detect mailto: things.

[curbengh]

Superseded by #3847.