Use Cache to determine if filter is enabled

[jiangtj]

Check List

Please check followings before submitting a new feature request.

• I have already read Docs page
• I have already searched existing issues

Feature Request

https://github.com/hexojs/hexo/blob/master/lib/plugins/filter/after_render/meta_generator.js

Currently, the meta_generator filter has performance problems. It is recommended to use a helper, but regular matching will still be used.

Maybe use Cache is a good solution.

function metaGeneratorHelper() {
  cache.set('meta_generator', true);
  return `<meta name="generator" content="Hexo ${this.env.version}">`;
}

function hexoMetaGeneratorInject(data) {
  let flag = cache.get('meta_generator');
  if (flag) return;
  const { config } = this;
  //...
}

Others

#4047 Inject can also do this, if use helpers in the theme, can improve performance.

[SukkaW]

I assume what you mean is a global plugins' status manager.

[SukkaW]

We could add this.prop = {} into helper's constructor(), And set ctx.extend.helper.prop.meta_generator = true inside meta_generator().

Later in meta_generator filter we could read this.extend.helper.prop.meta_generator to determine if meta_generator() helper is used or not.