Vim LSP Not Working - Fix Language Server Protocol Issues

# Vim LSP Not Working

Language Server Protocol (LSP) provides modern IDE features like autocomplete, go-to-definition, and diagnostics. But setting it up can be tricky. If LSP isn't working in Vim, here's how to debug and fix it.

Understanding LSP Components

LSP requires:

1. 1.LSP Client - Plugin in Vim that talks to language servers
2. 2.Language Server - External program (like pyright, tsserver)
3. 3.Configuration - Connecting client to server

Check LSP Status

Neovim (Native LSP)

:LspInfo
:LspLog

Check if server is attached:

:lua print(vim.lsp.get_active_clients()[1].name)

coc.nvim

:CocInfo
:CocList services

Check language server status:

:CocCommand languageserver.check

vim-lsp

:LspStatus
:LspLog

Language Server Not Starting

Server Not Installed

Install the language server for your language:

```bash # Python pip install pyright # Or pip install python-lsp-server

# TypeScript/JavaScript npm install -g typescript typescript-language-server

# Go go install golang.org/x/tools/gopls@latest

# Rust rustup component add rust-analyzer

# C/C++ brew install llvm # macOS # Or install clangd from system package manager ```

Server Not in PATH

Check if server is executable:

which pyright
which tsserver
which gopls

If not found, either install or add to PATH.

Configuration Missing

The LSP client needs configuration to start servers.

#### Neovim Native LSP

```lua local lspconfig = require('lspconfig')

lspconfig.pyright.setup{} lspconfig.tsserver.setup{} lspconfig.gopls.setup{} ```

#### coc.nvim

// In coc-settings.json
{
    "languageserver": {
        "python": {
            "command": "pyright",
            "filetypes": ["python"]
        }
    }
}

#### vim-lsp

if executable('pyright')
    au User lsp_setup call lsp#register_server({
        'name': 'pyright',
        'cmd': {server_info->['pyright']},
        'whitelist': ['python'],
    })
endif

No Completion Appearing

Completion Not Configured

For Neovim, you need a completion plugin:

local cmp = require('cmp')
cmp.setup({
    sources = {
        { name = 'nvim_lsp' },
    },
    mapping = {
        ['<Tab>'] = cmp.mapping.select_next_item(),
        ['<CR>'] = cmp.mapping.confirm({ select = true }),
    }
})

Trigger Character Not Hit

Some completion requires trigger characters. Check:

:lua print(vim.lsp.get_active_clients()[1].capabilities)

Completion Disabled

Check completion settings:

:set completefunc?
:set omnifunc?

Should show something like v:lua.vim.lsp.omnifunc.

No Diagnostics Showing

Diagnostics Disabled

Neovim:

vim.lsp.handlers["textDocument/publishDiagnostics"] = vim.lsp.with(
    vim.lsp.diagnostic.on_publish_diagnostics, {
        virtual_text = true,
        signs = true,
    }
)

No Errors in File

The file might not have errors. Check with:

:lua print(#vim.lsp.diagnostic.get(0))

Sign Column Hidden

Enable sign column:

set signcolumn=yes

Go-To-Definition Not Working

No Reference Data

Language server might not have parsed the file. Wait for initialization.

Check if server supports it:

:lua print(vim.lsp.get_active_clients()[1].resolved_capabilities.goto_definition)

Key Mapping Missing

Set up key mappings:

vim.keymap.set('n', 'gd', vim.lsp.buf.definition, {})
vim.keymap.set('n', 'gD', vim.lsp.buf.declaration, {})
vim.keymap.set('n', 'gr', vim.lsp.buf.references, {})

For coc.nvim:

nmap <silent> gd <Plug>(coc-definition)
nmap <silent> gr <Plug>(coc-references)

LSP Server Crashes

Server Memory Limits

Some servers (especially for large projects) need memory:

lspconfig.pyright.setup{
    settings = {
        python = {
            analysis = {
                memory = 4096,
            }
        }
    }
}

Server Timeout

Increase timeout:

lspconfig.tsserver.setup{
    cmd = {'typescript-language-server', '--stdio'},
    init_options = {
        maxTsServerMemoryLimit = 4096,
    }
}

Check Logs

:LspLog
:e ~/.cache/nvim/lsp.log

Multiple Servers Conflict

If multiple servers attach to same buffer:

:lua print(vim.inspect(vim.lsp.get_active_clients()))

Filter by filetype:

lspconfig.pyright.setup{
    filetypes = {'python'},
}

Project Root Detection

LSP needs to find project root. If it doesn't:

lspconfig.tsserver.setup{
    root_dir = lspconfig.util.root_pattern('package.json', 'tsconfig.json', '.git'),
}

Or specify manually:

lspconfig.pyright.setup{
    root_dir = function()
        return vim.fn.getcwd()
    end
}

Workspace Configuration

Some servers need workspace settings:

lspconfig.rust_analyzer.setup{
    settings = {
        ['rust-analyzer'] = {
            checkOnSave = {
                command = 'clippy',
            },
        }
    }
}

Slow LSP Response

File Parsing Delay

Large files take time to parse. Be patient after opening.

Reduce Analysis

lspconfig.pyright.setup{
    settings = {
        python = {
            analysis = {
                autoSearchPaths = false,
                diagnosticMode = 'openFilesOnly',
            }
        }
    }
}

Disable Hover

vim.lsp.handlers['textDocument/hover'] = function() end

coc.nvim Specific Issues

Extension Not Installed

:CocInstall coc-pyright
:CocInstall coc-tsserver
:CocInstall coc-go

Extension Disabled

:CocList extensions

Enable disabled extensions:

:CocEnableExtension coc-pyright

Configuration Wrong

Edit settings:

:CocConfig

Check JSON is valid:

:CocInfo

vim-lsp Specific Issues

Server Not Registered

:LspStatus

If empty, check registration:

:echo lsp#get_allowed_servers()

Auto-Start Disabled

let g:lsp_auto_enable = 1

LSP Debug Checklist

1. 1.Check server installed: which pyright
2. 2.Check server runs: pyright --version
3. 3.Check LSP client loaded: :LspInfo
4. 4.Check server attached: :lua print(vim.lsp.get_active_clients())
5. 5.Check logs: :LspLog
6. 6.Check completion source: :lua print(vim.inspect(require('cmp').get_config().sources))
7. 7.Check diagnostics: :lua print(#vim.lsp.diagnostic.get(0))
8. 8.Check root directory detected
9. 9.Check filetype matches server whitelist
10. 10.Check key mappings exist

Complete Neovim LSP Setup

```lua -- Install lspconfig local lspconfig = require('lspconfig')

-- Setup servers lspconfig.pyright.setup{} lspconfig.tsserver.setup{} lspconfig.gopls.setup{}

-- Completion local cmp = require('cmp') cmp.setup({ sources = { { name = 'nvim_lsp' } }, mapping = { ['<Tab>'] = cmp.mapping.select_next_item(), ['<CR>'] = cmp.mapping.confirm({ select = true }), } })

-- Keymaps vim.keymap.set('n', 'gd', vim.lsp.buf.definition) vim.keymap.set('n', 'K', vim.lsp.buf.hover) vim.keymap.set('n', '<leader>r', vim.lsp.buf.rename)

-- Diagnostics vim.lsp.handlers['textDocument/publishDiagnostics'] = vim.lsp.with( vim.lsp.diagnostic.on_publish_diagnostics, { virtual_text = true, signs = true, } ) ```

Quick Reference

```vim " Neovim native LSP :LspInfo :LspLog :LspStart :LspStop

" coc.nvim :CocInfo :CocInstall coc-pyright :CocConfig

" vim-lsp :LspStatus :LspLog

" Check clients :lua print(vim.inspect(vim.lsp.get_active_clients()))

" Keymaps (Neovim) gd " Go to definition K " Hover gr " References <leader>r " Rename ```

LSP setup requires installing servers, configuring clients, and connecting them. Check each component systematically when issues arise.