bad comment behavior in cmake files

Question

When I'm editing a cmake file in (neo)vim I'm getting bad behavior block inserting comment characters.

Given this section of text

    install_license_file(
        PACKAGE tomcrypt
        TARGET tomcrypt::tomcrypt
        VERSION "1.18"
        TYPE "PD"
        FILE "/usr/share/doc/libtomcrypt1/copyright"
    )

If I put the cursor at the start of install_license_file and then do this sequence

1. ctrl-v
2. 6j
3. I
4. #

I end up with this

 #install_license_file(
        PACKAGE tomcrypt
        TARGET tomcrypt::tomcrypt
        VERSION "1.18"
        TYPE "PD"
        FILE "/usr/share/doc/libtomcrypt1/copyright"
    )

but I'm trying to get this

   #install_license_file(
   #    PACKAGE tomcrypt
   #    TARGET tomcrypt::tomcrypt
   #    VERSION "1.18"
   #    TYPE "PD"
   #    FILE "/usr/share/doc/libtomcrypt1/copyright"
   #)

What's causing the unexpected behavior?

** UPDATE **

• if I completely clear out my init.vim and the system level sysinit.vim (Arch Linux) it works as expected but then if I do set shiftwidth=2 I get the bad behavior.
• if I start with nvim -u NONE I get the expected behavior even after set shiftwidth=2

Answer 1

You can reproduce this behavior in stock Vim with no extra plug-ins.

The reason why this issue happens is that 'indentkeys' includes 0#, which triggers automatic reindentation of a line when you type # as the first character of the line.

(Note that this is mostly meant for the C/C++ language, for directives such as #define or #include which are meant to appear on the first column even when they appear in the middle of an indented block.)

It appears that the change in indentation is enough to break the visual block insert that repeats the insertion on every line of the block, probably because the insertion is meant to happen on a specific column, but the change of indentation messes up with the column where text in inserted in the first line, so Vim probably just gives up and keeps the insertion to that line alone.

The reason why this issue doesn't happen in vim -u NONE is that, even though 'indentkeys' includes 0# in that case (it's part of the default), the 'indentexpr' option isn't set in that case, and 'indentkeys' only does something when 'indentexpr' is set. (You can easily reproduce this issue under vim -u NONE by using :set indentexpr=0.)

The reason why this issue doesn't happen in a Python script is that the ftplugin for python explicitly removes 0# from 'indentkeys'. (You could argue that the ftplugin for cmake should do the same, since both languages use # to mark comments.)

The workaround I would recommend is that you add an ftplugin script for cmake that will remove 0# from 'indentkeys'.

You can do so by creating a file ~/.config/nvim/after/ftplugin/cmake.vim (that's on NeoVim, or ~/.vim/after/ftplugin/cmake.vim on Vim for Linux/Unix, or %HOME%\vimfiles\after\ftplugin\cmake.vim on Vim for Windows), with the following command in it:

setlocal indentkeys-=0#

This file will be loaded after the ftplugin from Vim runtimes is loaded and will update 'indentkeys' to remove the setting that is breaking your particular use case.