How do I extend an existing filetype plugin?

You can extend an existing filetype plugin by creating a file in the after/ directory in any of the ‘runtimepath’ directories. - for small changes to be done after (and in addition to) what is already done by the ftplugin installed with Vim, use an after-directory, as follows (replacing foobar by the ‘filetype’ of the concerned files): - For changes private to one user: - on Windows: $HOME/vimfiles/after/ftplugin/foobar.vim - on Unix-like OSes: $HOME/.vim/after/ftplugin/foobar.vim - For changes affecting all users on the system: $VIM/vimfiles/after/ftplugin/foobar.vim - when replacing the whole filetype-plugin by a different version, or when installing a new ftplugin for some filetype not yet supported by Vim out of the box: use the same paths without the after/ in them. In that case you should place near the start of your plugin an “if… finish… endif… let” block like the one in the plugins distributed with Vim. All the above paths are given in Vim terminology (which is similar to Unix terminology, but is understood even by Vim for Windows); they don’t exist by default, so the first time you need them you will have to create them using mkdir (on any OS including DOS/Windows) or md (on DOS/Windows only). $VIM and, on DOS/Windows, $HOME, do not necessarily exist outside Vim. If $HOME has no value (or no valid value) inside Vim, you can use $VIM instead; but on any but possibly very old versions of Windows, $HOMEDRIVE and $HOMEPATH are defined by the system, and if $HOME is undefined at Vim startup, Vim will set it by expanding $HOMEDRIVE$HOMEPATH before sourcing your vimrc. To know which values Vim uses, you can type (in a running Vim):

    :echo $VIM

    :echo $HOME

If you placed the file in the after/ftplugin runtime directory, then Vim will first source the existing filetype plugin file and then will source the new file. If you placed the file in the $VIMRTUNTIME/ftplugin runtime directory, then Vim will first source the new file and then will source the existing filetype plugin file.