Multi-line completion inserts have "^@" instead of newlines

[Terr]

Multi-line inserts, like overriding a parent method in Python or complex Rust functions defined by traits, are inserted with a "^@" (null character? \n?) instead.

I've managed to produce this with two language servers, pyright and rust-analyzer.

Pyright:

Rust-analyzer:

Vim version: 9.1.1033
LSP revision: 68a3696 (latest as of writing this)

I used this mostly clean vimrc to reproduce it:

set nocompatible

" Plugins
call plug#begin('~/.vim/plugged')
"" Language server client
Plug 'yegappan/lsp'
call plug#end()

"" lsp

""" Configuration
autocmd User LspSetup call LspOptionsSet(#{
    \ autoHighlight: v:true,
    \ autoHighlightDiags: v:true,
    \ showInlayHints: v:true,
    \ showDiagsWithVirtualText: v:true,
\ })

""" Language server definitions
let lspServers = [#{
    \  name: 'pyright',
    \  filetype: 'python',
    \  path: 'pyright-langserver',
    \  args: ['--stdio'],
    \  workspaceConfig: #{
    \    python: #{
    \      pythonPath: 'python3'
    \  }}
    \},
    \#{
    \  name: 'rust-analyzer',
    \  filetype: ['rust'],
    \  path: 'rust-analyzer',
    \  args: [],
    \  syncInit: v:true,
    \  initializationOptions: #{
    \    inlayHints: #{
    \      typeHints: #{
    \        enable: v:true
    \      },
    \      parameterHints: #{
    \        enable: v:true
    \      }
    \    },
    \  }
    \}
\]

autocmd User LspSetup call LspAddServer(lspServers)

[berggeist]

This seems to be a known limitation of vim that multiline inserts are not (yet) supported:
Proposal: multiline completion support #2505

There is a draft pull-request for solving this in vim:
feat(completion): support insert special characters when completion #15373

[Terr]

Interesting, I wasn't expecting it to be a limitation of vim because coc.nvim is able to insert multiple lines. I wonder how it does it.

edit: as far as I can tell coc.nvim overrides some things, takes completion items coming from it's Node.js backend and inserts them like they are snippets.