Trouble in overriding `indentexpr` in neovim

Question

Say I do not quite like the shipped Lua indentexpr (GetLuaIndent(), defined in $VIMRUNTIME/indent/lua.vim). With vim, I can disable or change it using this minimal configuration:

~ % cat .vimrc
filetype indent on
filetype plugin on
~ % tree .vim/
.vim/
└── after
    └── ftplugin
        └── lua.vim

3 directories, 1 file
~ % cat .vim/after/ftplugin/lua.vim
setlocal indentexpr=

So next time I open up a Lua file, executing :set indentexpr? returns indentexpr=, and :scriptnames gives something like this:

:scriptnames
  1: /Applications/MacVim.app/Contents/Resources/vim/vimrc
  2: ~/.vimrc
  3: /Applications/MacVim.app/Contents/Resources/vim/runtime/filetype.vim
  4: /Applications/MacVim.app/Contents/Resources/vim/runtime/indent.vim
  5: /Applications/MacVim.app/Contents/Resources/vim/runtime/ftplugin.vim
  6: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/getscriptPlugin.vim
  7: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/gzip.vim
  8: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/logiPat.vim
  9: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/manpager.vim
 10: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/matchparen.vim
 11: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/netrwPlugin.vim
 12: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/rrhelper.vim
 13: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/spellfile.vim
 14: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/tarPlugin.vim
 15: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/tohtml.vim
 16: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/vimballPlugin.vim
 17: /Applications/MacVim.app/Contents/Resources/vim/runtime/plugin/zipPlugin.vim
 18: /Applications/MacVim.app/Contents/Resources/vim/runtime/indent/lua.vim
 19: /Applications/MacVim.app/Contents/Resources/vim/runtime/ftplugin/lua.vim
 20: ~/.vim/after/ftplugin/lua.vim

(no idea why $VIMRUNTIME uses MacVim's, but at least $VIMRUNTIME/indent/lua.vim was sourced before ~/.vim/after/ftplugin/lua.vim)

---

I then tried to replicate this behaviour in neovim, having:

.config % tree nvim/
nvim
└── after
    └── ftplugin
        └── lua.lua

3 directories, 1 file
.config % cat nvim/after/ftplugin/lua.lua
vim.bo.indentexpr = ''

Not effective as :set indentexpr? still gives indentexpr=GetLuaIndent() as before. Surprisingly and unsurprisingly, it turns out that $VIMRUNTIME/indent/lua.vim, this time, was sourced AFTER my custom ftplugin:

:scriptnames
  1: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/ftplugin.vim
  2: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/indent.vim
  3: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/filetype.lua
  4: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/syntax/syntax.vim
  5: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/syntax/synload.vim
  6: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/gzip.vim
  7: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/health.vim
  8: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/matchit.vim
  9: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/pack/dist/opt/matchit/plugin/matchit.vim
 10: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/matchparen.vim
 11: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/netrwPlugin.vim
 12: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/rplugin.vim
 13: ~/.local/share/nvim/rplugin.vim
 14: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/shada.vim
 15: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/spellfile.vim
 16: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/tarPlugin.vim
 17: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/tohtml.vim
 18: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/tutor.vim
 19: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/zipPlugin.vim
 20: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/editorconfig.lua
 21: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/man.lua
 22: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/plugin/nvim.lua
 23: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/ftplugin/lua.vim
 24: ~/.config/nvim/after/ftplugin/lua.lua
 25: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/indent/lua.vim
 26: /opt/homebrew/Cellar/neovim/0.9.0/share/nvim/runtime/syntax/lua.vim

Should I expect this? No idea. But since my ftplugin will be sourced earlier, maybe I can skip sourcing $VIMRUNTIME/indent/lua.vim by setting up the b:did_indent variable:

vim.cmd[[
if exists("b:did_indent")
  finish
endif
let b:did_indent = 1
]]
vim.bo.indentexpr = ''
print('set b:did_indent to ' .. vim.b.did_indent)

...since $VIMRUNTIME/indent/lua.vim starts with this:

if exists("b:did_indent")
  finish
endif
let b:did_indent = 1

Then I opened a Lua file and saw set b:did_indent to 1, however :set indentexpr? still gave me indentexpr=GetLuaIndent(). I am so confused. Are these expected behaviours? What can I do to effectively customise the indentexpr?

Answer 1

My recommendation is to move your code into: nvim/after/indent/lua.vim

setlocal indentexpr=

The indent folders are processed after the ftplugin folder and are indented to be used to set the indentation options (like their name suggest).