Add customize highlight.theme custom path support

[huang-x-h]

Motivation

Add customize highlight.theme custom path support. Fixes #428

eg:

  highlight: {
    theme: '/somepath/solarized-dark.min.css',
  },
  separateCss: ['solarized-dark'],

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Test success on local

Related PRs

N/A

[JoelMarcey]

@huang-x-h Hi. Sorry for the delay here. I am currently on vacation. I will have a thorough review of this as soon as I can.

[yangshun]

Thanks for the PR @huang-x-h ! Please have a look at the suggestions in the comments. If you would not be available to fix this, just let us know and we can take over 😄

[yangshun]

It's not a good idea to let the theme be either a string or a URL as this leads to confusing configuration. It's better to add a new field in highlight object called themeUrl and the code here uses it directly instead of building up the URL from the version and theme. Do remember to add this new URL to the siteConfig documentation.

Define a new variable highlightThemeURL instead. Don't reassign a value of a different type to the highlight variable.

// Use user-provided themeUrl if it exists, else construct one from version and theme.
let highlightThemeURL = highlight.themeUrl || `//cdnjs.cloudflare.com/ajax/libs/highlight.js/${highlight.version}/styles/${highlight.theme}.min.css`;

// Use highlightThemeURL in the `<link>`.

[yangshun]

This is not a very strong check. There's no guarantee that themes cannot have slashes in it in the future. Refer to comment below about using a themeUrl field as a check.

[yangshun]

Define a new variable highlightURL instead. Don't reassign a value of a different type to the highlight variable.

[yangshun]

Thanks for removing this 👍

[huang-x-h]

@yangshun thank you for your review, it's fixed.

[yangshun]

@JoelMarcey Please have a final look

[JoelMarcey]

Looks great to me. Should go out in the next release!