**Background**
This feature is part of the WMDE TechWish project "Making working with templates easier". It is specifically about improving template syntax and the ability to create and maintain templates. It will be implemented as a part of the syntax highlighter of the CodeMirror extension. Line numbering helps to easily and quickly display where line breaks are in a standard format.
**Implementation plan: will be released without feature flag; data is still TBD. Do not implement until date has been set by Product.**
**Requirements**
[] Enable line numbering in both 2010 and 2017 wikitext editors in the syntax highlighter (CodeMirror extension)
[] In the 2017 wikitext editor, update styling to remove the background gray and add padding (see below).
[] In the 2010 wikitext editor, match styling to CodeEditor line numbering
[] Fix styling issues in 2017 wikitext editor (check implementation on test instance, see https://gitlab.com/wmde/mediawiki-extensions-CodeMirror/-/commit/7b4ad47e9c1cc8ca2cd02d4e7b9934b1eec61f24)
[] Implement behind feature flag - investigate options
[] Enable in syntax highlighter by default
**Mocks and Specs**
Wikitext 2010 editor: match CodeEditor line numbering styling but without the added space needed for code folding arrows. No outline on right-hand size of numbered area. (Note the number color may be updated. If so, match: {T271956})
{F34111770}
Wikitext 2017 editor (VE): Numbers should be Base 70 with 8px padding between them and the wikitext. (Matches iOS editor implementation)
|{F34111738}| {F34111741}|