refactor(nunjucks): dedicated nunjucks renderer

[SukkaW]

What does it do?

The continuation of #2903.

In every case, hexo-renderer-* is considered as a plugin of hexo (not a dependency of hexo). When hexo uses swig as a default renderer, hexo-swig-renderer exists but it is not a dependency of hexo.

In this PR I remove hexo-renderer-nunjucks and bring up a dedicated nunjucks renderer.

I have written a custom toArray to avoid lodash.toarray,

How to test

git clone -b split-nunjucks 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.

[jiangtj]

I tested the forked next theme from mimi, but got error. Is there any difference between next built-in and this? @stevenjoezhang

# create project
hexo init test-dir
cd test-dir
# fork and use next theme
git clone https://github.com/next-theme/hexo-theme-next themes/next
rm themes/next/scripts/renderer.js
hexo config theme next
# use this hexo version
yarn add sukkaw/hexo#split-nunjucks
# run
hexo cl && hexo s

[SukkaW]

@jiangtj

It appears that there are some nunjucks filters added by @stevenjoezhang in next-theme (For example json filter).

Also, the PR (migrated from @oncletom) uses fs.readFileSync, while @stevenjoezhang let nunjucks resolves the template file path.

[SukkaW]

@stevenjoezhang I could include json filter in the PR as well if you wish.

[stevenjoezhang]

I would appreciate if the json filter could be included. The Nunjucks build-in filter dump does not handle undefined value.
https://mozilla.github.io/nunjucks/templating.html#dump

[SukkaW]

@stevenjoezhang A new filter safeDump has been added and test cases are introduced.

[coveralls]

Coverage remained the same at 97.742% when pulling 821e075 on SukkaW:split-nunjucks into 600b43a on hexojs:master.

[curbengh]

I tested the forked next theme from mimi, but got error. Is there any difference between next built-in and this?

Tested with latest PR update, same error.

[SukkaW]

@curbengh I have ported the nunjucks renderer from @stevenjoezhang. This time the nunjucks renderer should work.

[curbengh]

WFM, this time I didn't remove themes/next/scripts/renderer.js.

[SukkaW]

this time I didn't remove themes/next/scripts/renderer.js.

@curbengh Remove it and try again see if it works?

[curbengh]

Is it supposed to get removed? I got following error after remove:

ERROR Template render error: (themes/next/layout/page.njk)
  Error: template not found: _layout.njk

[SukkaW]

Is it supposed to get removed? I got following error after remove:

Yes. New NexT theme has a built-in nunjucks renderer which should be removed after this PR is merged (As the PR is attempt to replace it).

There must be something wrong with relative path resolving.
Help wanted. @stevenjoezhang

[thom4parisot]

I do not understand the difference between "dedicated renderer" and "a plugin of hexo" (as a user feature).

The initial intent of providing the renderer as a plugin was to uncouple the rendering with hexo mecanics — this way, defaulting to a different renderer is just a matter of switching a renderer dependency from one to another.

What you are doing here is fairly good addition to the core plugin, it would totally make sense you contribute it upstream.

[SukkaW]

Rebased.

@stevenjoezhang Would you mind reviewing the PR again?
@oncletom Would you mind adding your review?

@curbengh Try removing next-theme's nunjucks.js and try this PR again? My local dummy blog shows fine.

[curbengh]

You mean themes/next/scripts/renderer.js? Same error even with the latest commit (of this PR).

Error: template not found: _layout.njk

[SukkaW]

@curbengh This time should work.

[jiangtj]

LGTM!