This plugin extends the Code block in WordPress core to add syntax highlighting which is rendered on the server. Pre-existing Code blocks on a site are automatically extended to include syntax highlighting. Doing server-side syntax highlighting eliminates the need to enqueue any JavaScript on the frontend (e.g. Highlight.js or Prism.js) and this ensures there is no flash of unhighlighted code (FOUC?). Reducing script on the frontend improves frontend performance and it also allows for the syntax highlighted code to appear properly in AMP pages as rendered by the official AMP plugin (see also ampproject/amp-wp#972) or when JavaScript is turned off in the browser. In addition to not adding any JavaScript to the frontend, the stylesheets needed for styling the Code block will only be added to the page if there is a Code block present. The stylesheets are added inline when the Code block is rendered, ensuring that they do not block rendering of any content higher in the page. If stylesheets fail to load for any reason, the block simply renders without styling, with one key exception: highlighted lines are wrapped in mark elements so they’ll get highlighted regardless, including in RSS Feeds and posts syndicated in email (as long as the mark element is supported in the client). This extended Code block uses language auto-detection to add syntax highlighting, but you can override the language in the block’s settings sidebar. (There is currently no syntax highlighting of the Code block in the editor.) The plugin supports all programming languages that highlight.php supports (being a port of highlight.js). The Code block also is extended to support specifying the aforementioned highlighted lines. There is also a checkbox for whether to show line numbers on the frontend (with the numbers being non-selectable). Lastly, given inconsistencies across themes as to whether lines in
