I noticed that the TODO part of #TODO is highlighted in yellow when editing Python files using Vim. How can I add custom highlighting? For example, I want the BUG part of #BUG to be highlighted in red.
I searched for some answers, but they are too complicated and did not achieve the desired matching effect.
Does anyone have a better method?
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You can do this by introducing a new group into Vim’s Python syntax definition.
The original definition can be found in $VIMRUNTIME/syntax/python.vim and can serve as a reference.
Tweaks for built-in files are supposed to go into the after files of your user’s Vim directory, e.g. ~/.vim/after/syntax/python.vim or $HOME/vimfiles/after/syntax/python.vim on Windows.
You may create the directories and the file if they don’t already exist.
This file will be :sourced after the global config.
Refer to the documentation in :help runtimepath and :help after-directory.
The following lines need to go into ~/.vim/after/syntax/python.vim:
syntax match pythonComment "#.*$" contains=pythonBug,pythonTodo,@Spell
syntax keyword pythonBug BUG contained
highlight link pythonBug Error
The first line is copied from the global syntax file and we just add our new syntax group pythonBug.
Now comments can also contain pythonBug just as they can contain pythonTodo (the group responsible for highlighting “TODO” etc.).
The second line defines that pythonBug should match the keyword “BUG” but only if it’s contained within another group (that’s pythonComment).
The third line links the appearance of pythonBug to Error which will – depending on your colorscheme – probably be something reddish. You can also browse all known highlight groups with :highlight and pick one you like better.
While it’s possible to explicitly give “BUG” a red background, it’s better to let the colorscheme take care of the actual colors.
Notable sections of the documentation are :help :syn-keyword and :help :highlight.