Exact instructions how to setup fortls with neovim

[certik]

I tried several times and always failed to get (any) LSP working with neovim, and I just figured it out specifically for fortls. I am documenting here the exact steps before I forget. We can later move this into fortls documentation.

The setup below does not destroy your current neovim setup. It makes it completely optional. You can use the NVIM_APPNAME environment variable to choose between setups.

1. First install lazyvim:

# check that ~/.config/lazyvim does not exist. If it does, archive it, or change the directory below
git clone https://github.com/LazyVim/starter ~/.config/lazyvim
export NVIM_APPNAME=lazyvim
nvim some_file.f90

The first time you start neovim with this setup, it will load all plugins and install itself. The subsequent time will be quite fast (although not as fast as vanilla neovim unfortunately and there are other issues, such as flicker at startup, sometimes the cursor movement is lagging; so I do not have lazyvim on by default due to these issues).

2. Install conda: Use https://github.com/conda-forge/miniforge and follow the instructions there.

3. Install fortls:

mamba create -n fortls python
conda activate fortls
pip install fortls
echo 'require("lspconfig").fortls.setup({})' >> ~/.config/lazyvim/init.lua
nvim some_file.f90

Check that fortls is loaded using :checkhealth lsp. Now you can use the commands listed at https://dev.to/vonheikemen/getting-started-with-neovims-native-lsp-client-in-the-year-of-2022-the-easy-way-bp3. I found that the following three commands work: K, gd, gr. Here is an example of K:

Also TAB completion works in insert mode:

[certik]

I think I figured out how to make it work without lazyvim.

git clone https://github.com/neovim/nvim-lspconfig ~/.config/nvim/pack/nvim/start/nvim-lspconfig

Add this into init.vim:

lua << EOF
require'lspconfig'.fortls.setup{}
EOF

(or just the middle line into init.lua)

Only K and gd works for me, here is K:

Yes, colors are not the best, but I am sure that can be fixed.

gd only finds the symbol in the current file, it doesn't seem to go to another file for some reason.

Tab completion does not work (maybe I don't know how to use it).

[gnikit]

Just saw this @certik (sorry...). I use the native LSP implementation of neovim, to configure fortls and don't pass it through lazyvim since the language server will not activate unless a Fortran file is opened.
I add only a little stub to my init.lua

require'lspconfig'.fortls.setup{
    cmd = {
        'fortls',
        '--lowercase_intrisics',
        '--hover_signature',
        '--hover_language=fortran',
        '--use_signature_help'
    }
}

I added it to the docs when I switched from vim to neovim.

I will try and setup it up on my new mac and update the instructions if they are out of date.