refactor/perf(post): use state machine to escape swig tag

[SukkaW]

What does it do?

Replace regexp with the state machine.

How to test

git clone -b post-render-escape-swig https://github.com/sukkaw/hexo.git
cd hexo
npm install
npm test

Screenshots

Pull request tasks

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

[SukkaW]

The self-recursive escaping is firstly introduced by @seaoak in #2321 trying to mitigate a back_tick_code inside a swig tag issue when the year is 2016. Since then, Hexo's post rendering mechanics has changed dramatically. When #2321 being merged in 2019, there is no longer required self-recursive as nested escaping will never happen. After this change, the unit test case still passed.

[stevenjoezhang]

The rendering of left curly brackets has been changed in this pull request, which will affect the display of mathematical formulas (\begin{equation} becomes \beginequation})

Unit tests: https://github.com/hexojs/hexo/tree/post-render

[SukkaW]

The rendering of left curly brackets has been changed in this pull request, which will affect the display of mathematical formulas (\begin{equation} becomes \beginequation})

Unit tests: https://github.com/hexojs/hexo/tree/post-render

Ouch. I thought I have solved the issue. I will look into it now.

[stevenjoezhang]

There is another issue, the following markdown document will cause a rendering error

Disable rendering of Nunjucks tag `{{ }}`/`{% %}` and [tag plugins](/docs/tag-plugins) when enabled

See https://github.com/hexojs/site/runs/3680904140