clangd completion does not work

[kwon-young]

Hello,
Following this thread: https://www.reddit.com/r/neovim/comments/6j12mr/getting_clangd_llvms_lsp_implementation_for_c_to/
I decided to try and make the clangd language server for c++ work.
However, I obtained the same results where the linting of errors works but the completion using deoplete and python3 does not.
Following the advice of ShougoMatsu, i'm creating this issue to provide more detailed information.

• OS: manjaro/Linux
• neovim version: v0.2.0
• Plugin version (git SHA): 223857f
• Minimal vimrc:

call plug#begin('~/.vim/plugged')
Plug 'Shougo/deoplete.nvim', { 'do': ':UpdateRemotePlugins' }
Plug 'autozimu/LanguageClient-neovim', { 'do': ':UpdateRemotePlugins' }
call plug#end()
let g:deoplete#enable_at_startup = 1
set hidden
let g:LanguageClient_serverCommands = {
    \ 'cpp': ['clangd']
    \ }
let g:LanguageClient_autoStart = 1
let g:LanguageClient_trace = 'verbose'

• Content of :CheckHealth:

health#deoplete#check
========================================================================
## deoplete.nvim
  - SUCCESS: has("nvim") was successful
  - SUCCESS: has("python3") was successful
  - INFO: If you're still having problems, try the following commands:
    $ export NVIM_PYTHON_LOG_FILE=/tmp/log
    $ export NVIM_PYTHON_LOG_LEVEL=DEBUG
    $ nvim
    $ cat /tmp/log_{PID}
    and then create an issue on github

health#nvim#check
========================================================================
## Configuration
  - SUCCESS: no issues found

## Performance
  - SUCCESS: Build type: Release

## Remote Plugins
  - SUCCESS: Up to date

## terminal
  - INFO: key_backspace (kbs) terminfo entry: key_backspace=^H
  - INFO: key_dc (kdch1) terminfo entry: key_dc=\E[3~

health#provider#check
========================================================================
## Clipboard (optional)
  - SUCCESS: Clipboard tool found: xclip

## Python 2 provider (optional)
  - WARNING: No Python interpreter was found with the neovim module.  Using the first available for diagnostics.
  - WARNING: provider/pythonx: Could not load Python 2:
    /usr/bin/python2 does not have the "neovim" module. :help |provider-python|
    /usr/bin/python2.7 does not have the "neovim" module. :help |provider-python|
    python2.6 not found in search path or not executable.
    /usr/bin/python is Python 3.6 and cannot provide Python 2.
  - ERROR: Python provider error
    - SUGGESTIONS:
      - provider/pythonx: Could not load Python 2:
          /usr/bin/python2 does not have the "neovim" module. :help |provider-python|
          /usr/bin/python2.7 does not have the "neovim" module. :help |provider-python|
          python2.6 not found in search path or not executable.
          /usr/bin/python is Python 3.6 and cannot provide Python 2.
  - INFO: Executable: Not found

## Python 3 provider (optional)
  - INFO: `g:python3_host_prog` is not set.  Searching for python3 in the environment.
  - INFO: Executable: /usr/bin/python3
  - INFO: Python3 version: 3.6.1
  - INFO: python3-neovim version: 0.1.13
  - SUCCESS: Latest python3-neovim is installed: 0.1.13

## Ruby provider (optional)
  - INFO: Ruby: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux]
  - WARNING: Missing "neovim" gem.
    - SUGGESTIONS:
      - Run in shell: gem install neovim
      - Is the gem bin directory in $PATH? Check `gem environment`.
      - If you are using rvm/rbenv/chruby, try "rehashing".

• Content of ~/.local/share/nvim/rplugin.vim:

" python3 plugins
call remote#host#RegisterPlugin('python3', '/home/vim/.vim/plugged/LanguageClient-neovim/rplugin/python3/LanguageClient', [
      \ {'sync': v:true, 'name': 'LanguageClient_alive', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_completionItem/resolve', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_completionManager_refresh', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_exit', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_FZFSinkTextDocumentDocumentSymbol', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_FZFSinkTextDocumentReferences', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_FZFSinkWorkspaceSymbol', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'BufReadPost', 'type': 'autocmd', 'opts': {'pattern': '*'}},
      \ {'sync': v:false, 'name': 'CursorMoved', 'type': 'autocmd', 'opts': {'pattern': '*', 'eval': 'line(''.'')'}},
      \ {'sync': v:false, 'name': 'VimEnter', 'type': 'autocmd', 'opts': {'pattern': '*'}},
      \ {'sync': v:false, 'name': 'LanguageClient_initialize', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_registerServerCommands', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_setLoggingLevel', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClientStart', 'type': 'command', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClientStop', 'type': 'command', 'opts': {}},
      \ {'sync': v:false, 'name': 'TextChanged', 'type': 'autocmd', 'opts': {'pattern': '*'}},
      \ {'sync': v:false, 'name': 'TextChangedI', 'type': 'autocmd', 'opts': {'pattern': '*'}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_completion', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_completionOmnifunc', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_definition', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_didClose', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'BufWritePost', 'type': 'autocmd', 'opts': {'pattern': '*'}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_documentSymbol', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_formatting', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_hover', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_references', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_rename', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_textDocument_signatureHelp', 'type': 'function', 'opts': {}},
      \ {'sync': v:false, 'name': 'LanguageClient_workspace_symbol', 'type': 'function', 'opts': {}},
     \ ])
call remote#host#RegisterPlugin('python3', '/home/vim/.vim/plugged/deoplete.nvim/rplugin/python3/deoplete', [
      \ {'sync': v:true, 'name': '_deoplete', 'type': 'function', 'opts': {}},
     \ ])


" ruby plugins


" python plugins

• Run :call LanguageClient_setLoggingLevel('DEBUG') and then
  :LanguageClientStart, reproduce the bug (tried to do omni-completion), attach content of
  /tmp/LanguageClient.log:

Args: /home/vim/prog/llvm-build/bin/clangd -debug -stats 
17:45:46 WARNING  Unknown project type. Fallback to use dir as project root.
Content-Length: 168

{"jsonrpc": "2.0", "method": "initialize", "params": {"processId": 1763, "rootPath": "/tmp", "rootUri": "file:///tmp", "capabilities": {}, "trace": "verbose"}, "id": 0}<-- {"jsonrpc": "2.0", "method": "initialize", "params": {"processId": 1763, "rootPath": "/tmp", "rootUri": "file:///tmp", "capabilities": {}, "trace": "verbose"}, "id": 0}
Notification ignored.
17:46:01 INFO     Begin textDocument/completion
17:46:01 INFO     textDocument/didChange
17:46:01 INFO     textDocument/didOpen
17:46:01 DEBUG     => {"jsonrpc": "2.0", "method": "textDocument/didOpen", "params": {"textDocument": {"uri": "file:///tmp/main.cpp", "languageId": "cpp", "version": 1, "text": "class Foo {\n  public:\n    int bar;\n};\n\nint main(int argc, char* argv[]) {\n  Foo foo;\n  foo.\n  return 0;\n}\n"}}}
Content-Length: 276

{"jsonrpc": "2.0", "method": "textDocument/didOpen", "params": {"textDocument": {"uri": "file:///tmp/main.cpp", "languageId": "cpp", "version": 1, "text": "class Foo {\n  public:\n    int bar;\n};\n\nint main(int argc, char* argv[]) {\n  Foo foo;\n  foo.\n  return 0;\n}\n"}}}<-- {"jsonrpc": "2.0", "method": "textDocument/didOpen", "params": {"textDocument": {"uri": "file:///tmp/main.cpp", "languageId": "cpp", "version": 1, "text": "class Foo {\n  public:\n    int bar;\n};\n\nint main(int argc, char* argv[]) {\n  Foo foo;\n  foo.\n  return 0;\n}\n"}}}
17:46:01 DEBUG     => {"jsonrpc": "2.0", "method": "textDocument/completion", "params": {"textDocument": {"uri": "file:///tmp/main.cpp"}, "position": {"line": 7, "character": 6}}, "id": 1}
Content-Length: 166

{"jsonrpc": "2.0", "method": "textDocument/completion", "params": {"textDocument": {"uri": "file:///tmp/main.cpp"}, "position": {"line": 7, "character": 6}}, "id": 1}<-- {"jsonrpc": "2.0", "method": "textDocument/completion", "params": {"textDocument": {"uri": "file:///tmp/main.cpp"}, "position": {"line": 7, "character": 6}}, "id": 1}
Notification ignored.
--> {"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///tmp/main.cpp","diagnostics":[{"range":{"start": {"line": 8, "character": 3}, "end": {"line": 8, "character": 3}},"severity":1,"message":"expected unqualified-id"}]}}
Content-Length: 250

{"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///tmp/main.cpp","diagnostics":[{"range":{"start": {"line": 8, "character": 3}, "end": {"line": 8, "character": 3}},"severity":1,"message":"expected unqualified-id"}]}}17:46:01 DEBUG     <= {"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///tmp/main.cpp","diagnostics":[{"range":{"start": {"line": 8, "character": 3}, "end": {"line": 8, "character": 3}},"severity":1,"message":"expected unqualified-id"}]}}
17:46:12 INFO     Begin textDocument/completion
17:46:13 INFO     textDocument/didChange
17:46:13 DEBUG     => {"jsonrpc": "2.0", "method": "textDocument/didChange", "params": {"textDocument": {"uri": "file:///tmp/main.cpp", "version": 2}, "contentChanges": [{"text": "class Foo {\n  public:\n    int bar;\n};\n\nint main(int argc, char* argv[]) {\n  Foo foo;\n  foo.1\n  return 0;\n}\n"}]}}
Content-Length: 280

{"jsonrpc": "2.0", "method": "textDocument/didChange", "params": {"textDocument": {"uri": "file:///tmp/main.cpp", "version": 2}, "contentChanges": [{"text": "class Foo {\n  public:\n    int bar;\n};\n\nint main(int argc, char* argv[]) {\n  Foo foo;\n  foo.1\n  return 0;\n}\n"}]}}<-- {"jsonrpc": "2.0", "method": "textDocument/didChange", "params": {"textDocument": {"uri": "file:///tmp/main.cpp", "version": 2}, "contentChanges": [{"text": "class Foo {\n  public:\n    int bar;\n};\n\nint main(int argc, char* argv[]) {\n  Foo foo;\n  foo.1\n  return 0;\n}\n"}]}}
17:46:13 INFO     textDocument/didChange
17:46:13 DEBUG     => {"jsonrpc": "2.0", "method": "textDocument/completion", "params": {"textDocument": {"uri": "file:///tmp/main.cpp"}, "position": {"line": 7, "character": 7}}, "id": 2}
Content-Length: 166

{"jsonrpc": "2.0", "method": "textDocument/completion", "params": {"textDocument": {"uri": "file:///tmp/main.cpp"}, "position": {"line": 7, "character": 7}}, "id": 2}<-- {"jsonrpc": "2.0", "method": "textDocument/completion", "params": {"textDocument": {"uri": "file:///tmp/main.cpp"}, "position": {"line": 7, "character": 7}}, "id": 2}
Notification ignored.
--> {"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///tmp/main.cpp","diagnostics":[{"range":{"start": {"line": 7, "character": 6}, "end": {"line": 7, "character": 6}},"severity":1,"message":"expected ';' after expression"},{"range":{"start": {"line": 7, "character": 8}, "end": {"line": 7, "character": 8}},"severity":1,"message":"expected ';' after expression"},{"range":{"start": {"line": 7, "character": 3}, "end": {"line": 7, "character": 3}},"severity":2,"message":"expression result unused"},{"range":{"start": {"line": 7, "character": 6}, "end": {"line": 7, "character": 6}},"severity":2,"message":"expression result unused"}]}}
Content-Length: 666

{"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///tmp/main.cpp","diagnostics":[{"range":{"start": {"line": 7, "character": 6}, "end": {"line": 7, "character": 6}},"severity":1,"message":"expected ';' after expression"},{"range":{"start": {"line": 7, "character": 8}, "end": {"line": 7, "character": 8}},"severity":1,"message":"expected ';' after expression"},{"range":{"start": {"line": 7, "character": 3}, "end": {"line": 7, "character": 3}},"severity":2,"message":"expression result unused"},{"range":{"start": {"line": 7, "character": 6}, "end": {"line": 7, "character": 6}},"severity":2,"message":"expression result unused"}]}}17:46:13 DEBUG     <= {"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///tmp/main.cpp","diagnostics":[{"range":{"start": {"line": 7, "character": 6}, "end": {"line": 7, "character": 6}},"severity":1,"message":"expected ';' after expression"},{"range":{"start": {"line": 7, "character": 8}, "end": {"line": 7, "character": 8}},"severity":1,"message":"expected ';' after expression"},{"range":{"start": {"line": 7, "character": 3}, "end": {"line": 7, "character": 3}},"severity":2,"message":"expression result unused"},{"range":{"start": {"line": 7, "character": 6}, "end": {"line": 7, "character": 6}},"severity":2,"message":"expression result unused"}]}}

• minimal c++ code to do completion on line 7:

class Foo {
  public:
    int bar;
};

int main(int argc, char* argv[]) {
  Foo foo;
  foo.
  return 0;
}

I'll be happy to provide more information any time.
I've also tried the clangd language server using the visual studio code client and completion is working as expected.
I've also tried the ruby language server completion in neovim using this plugin and deoplete and it's working as expected.

[autozimu]

This is actually a bug of clangd, where vscode send requests like

{"jsonrpc": "2.0", "id": 0, "method": ..., "params": ...}

while this plugin send

{"jsonrpc": "2.0", "method:" ..., "params": ..., "id": 0}

Theoretically these should be equivalent, while in fact clangd thought the latter is a notification instead of a RPC call.

I will first push a commit to make this plugin behaviour identical to vscode does. Might later make PR or issue on clangd side.

[autozimu]

Thank you for creating this issue.

[autozimu]

https://github.com/llvm-mirror/clang-tools-extra/blame/803066819dde44fc5b8ab0359113177e661fad3e/clangd/JSONRPCDispatcher.cpp#L116

[kwon-young]

Thanks a lot!
It is now working as expected.
I just need now to figure out how i can configure clangd for project specific settings like compiler option and include paths.

[louwers]

@kwon-young Did you? Wondering how to do the same!

[kwon-young]

Since my last message, llvm released 5.0 with a first working version of clangd.
It's easy to get if you are under archlinux.
It's possible to use a compile_command.json if you generate one with cmake and put at the root of your project.
The thing that doesn't work yet is the integration with header files but it's being worked on.
In conclusion, I would say that it's basically working but not usable in a production environment.

[Dema]

Looks like new Rust implementation suffers from the same issue.
here is what is being sent to clangd server
<-- {"jsonrpc":"2.0","method":"textDocument/hover","params":{"position":{"character":4,"line":2},"textDocument":{"uri":"file:///home/dema/Sync/electronics/Arduino/robot2/src/main.cc"}},"id":31}
The id field is again sent as the last item.

[ErickChacon]

The rust implementation does not work for me too. This is being sent to the server:

{"jsonrpc":"2.0","method":"eval","params": ... ,"id":5}

[autozimu]

Unfortunately for this rust implementation, there is no simple way to workaround this language server bug.

If you want to get this fixed, push clangd side.

[Dema]

They don't have it either, unfortunately

[kwon-young]

From what I can see, this issue is resolved just by updating the latest clangd v6.
They changed their implementation in this commit llvm-mirror/clang-tools-extra@9140412 which should make this error go away.
I'm currently rebuilding clangd from svn to see if it works.
By the way, @autozimu, did you see the issue #334 I filed two days ago?
I've made some reproducible steps in order produce the bug.
@ferozco thinks it's a client bug.

[autozimu]

Confirmed clangd 6.0.0 has fixed the issue.

For macOS users, brew install llvm is enough to get latest llvm, and clangd is in /usr/local/opt/llvm/bin/clangd.