Adding Additional Syntax Highlight to nvim; cannot get .config/nvim/after/syntax to load .vim file

Question

I'm trying to add additional syntax highlighting to a plugin I'm using for syntax highlighting. I've tried adding the additional syntax file fstrings.vim to the ~/.config/nvim/after/syntax folder but my nvim is not picking it up.

Things I've tried:

1. Check if ~/.config/nvim/after and/or ~/.config/nvim/after/syntax is added to my runtime path.

• Only ~/.config/nvim/after is added to my path - checked with :set rtp >> runtimepath=~...,...,~/.config/nvim/after - however I don't see the file loaded in :scriptnames. How can I get the file to load?

2. Change location of the file to ~/.config/nvim/after instead of ~/.config/nvim/after/syntax

• This does not work either.

3. Manually load the file.

• This actually does work surprisingly. I can manually change the syntax of the file using :set syntax=fstrings however, all the original syntax highlighting provided by the plugin disappears, and only the highlighting provided (see the print statement in the image below) by the fstrings.vim is used. This leads me to believe the path is set up correctly however nvim does not want to load it during startup and/or ignores it because of the plugin being used.

I know the /after/ folder is used to apply settings after previous settings, rather than overwriting. I've already tried the solution here and here but I've not been able to make it work. Any help on how to debug this would be appreciated.

" ~/.config/nvim/after/syntax/fstrings.vim

syn match pythonEscape +{{+ contained containedin=pythonfString,pythonfDocstring
syn match pythonEscape +}}+ contained containedin=pythonfString,pythonfDocstring

syn region pythonfString matchgroup=pythonQuotes
      \ start=+[fF]\@1<=\z(['"]\)+ end="\z1"
      \ contains=@Spell,pythonEscape,pythonInterpolation
syn region pythonfDocstring matchgroup=pythonQuotes
      \ start=+[fF]\@1<=\z('''\|"""\)+ end="\z1" keepend
      \ contains=@Spell,pythonEscape,pythonSpaceError,pythonInterpolation,pythonDoctest

syn region pythonInterpolation contained
      \ matchgroup=SpecialChar
      \ start=+{{\@!+ end=+}}\@!+ skip=+{{+ keepend
      \ contains=ALLBUT,pythonDecoratorName,pythonDecorator,pythonFunction,pythonDoctestValue,pythonDoctest

syn match pythonStringModifier /:\(.[<^=>]\)\?[-+ ]\?#\?0\?[0-9]*[_,]\?\(\.[0-9]*\)\?[bcdeEfFgGnosxX%]\?/ contained containedin=pythonInterpolation
syn match pythonStringModifier /![sra]/ contained containedin=pythonInterpolation

hi link pythonfString String
hi link pythonfDocstring String
hi link pythonStringModifier PreProc

Answer 1

The syntax rules are typically named after the 'filetype' set for the buffer, which in turn is typically detected (based on file extension, file name, or file contents) and usually set automatically.

If you want to extend syntax highlighting for Python, then you should typically name your script after the "python" filetype.

When Vim loads syntax rules for Python, it will for files named syntax/python.vim or syntax/python/*.vim (the ftplugin rules also allow for python_*.vim, but it turns out that's not the case for syntax.)

So you should name your file ~/.config/nvim/after/syntax/python.vim (or ~/.config/nvim/after/syntax/python/fstrings.vim) in order to have it loaded for Python files and after the bundled runtime rules for Python are loaded.

---

Another option is to set the 'syntax' option to include multiple types, separated by a dot. For example, :setlocal syntax=python.fstrings will first load syntax/python.vim and then syntax/fstrings.vim. This would be more useful if you had a piece of syntax that's somewhat generic and can make sense for multiple separate languages (for example, some syntax highlighting to a documentation format inside comments?) It doesn't seem to be very applicable in this case, where f-strings are essentially a Python syntax. Maintaining a 'syntax' setting separate from the 'filetype' one can also be tricky, it needs to be set at the right location (not too early or too late) to avoid getting clobbered by the default setting.

---

While troubleshooting such an issue of a script of yours not being loaded, you can use the :scriptnames command to check whether your *.vim script was actually loaded by Vim at some point. Repeat that before and after opening a file of the specific filetype you're after to confirm it was triggered by that filetype detection.