SimpleCC

SimpleCC is a Vim 9 Language Server Protocol client with a small Rust daemon and a native Vim9 UI. The daemon owns language-server processes and JSON-RPC traffic; Vim handles completion, diagnostics, navigation, edits, snippets, inlay hints, semantic tokens, code lenses, and hierarchy views.

Requirements

• Vim 9.0 or newer with Vim9 script, jobs, channels, popups, timers, and text properties. A recent Vim 9.1 build is recommended.
• A stable Rust toolchain with Cargo to build the daemon.
• Bash and standard Unix tools for install.sh.
• At least one language server, installed on PATH or through :SimpleCCInstall.

The managed language-server installer targets Linux and macOS on x86_64 and aarch64. Other systems may still use a manually built daemon and servers already available on PATH, but are not currently covered by CI.

Installation

With vim-plug:

Plug 'beamiter/simplecc', { 'do': './install.sh' }

Run :PlugInstall, or rebuild an existing checkout:

cd ~/.vim/plugged/simplecc
./install.sh

For a manual package installation:

git clone https://github.com/beamiter/simplecc.git \
  ~/.vim/pack/plugins/start/simplecc
~/.vim/pack/plugins/start/simplecc/install.sh

The installer performs a reproducible cargo build --release --locked, stages the daemon, verifies it, and atomically replaces lib/simplecc-daemon. To keep the daemon elsewhere:

let g:simplecc_daemon_path = '/absolute/path/to/simplecc-daemon'

Quick start

1. Install SimpleCC and one language server.
2. Open a supported source file. SimpleCC starts automatically by default.
3. Check the state with :SimpleCC.
4. Use gd for definition, K for hover, and <leader>rn for rename.

For example:

:SimpleCCInstall rust-analyzer
:SimpleCCRestart

If a server is already installed system-wide, no managed installation is needed. SimpleCC resolves managed installations first and then searches PATH.

Configuration

Set an explicit configuration before the plugin loads:

let g:simplecc_config_path = expand('~/.config/simplecc/simplecc.json')

Without an explicit path, SimpleCC searches in this order:

1. simplecc.json in the detected project root.
2. .simplecc.json in the detected project root.
3. ~/.config/simplecc/simplecc.json.
4. Built-in defaults when no file exists.

Open or create the active project configuration with :SimpleCCConfig. :SimpleCCReloadConfig validates the replacement file and hot-pushes settings to servers that are already running. Changes to command, args, filetypes, rootPatterns, priority, or initializationOptions require :SimpleCCRestart. Invalid JSON is reported and does not silently replace the running configuration.

Minimal configuration:

{
  "languageServers": {
    "rust-analyzer": {
      "command": "rust-analyzer",
      "args": [],
      "filetypes": ["rust"],
      "rootPatterns": ["Cargo.toml"],
      "priority": 100,
      "initializationOptions": {},
      "settings": {}
    }
  }
}

Each language-server entry supports:

• command: executable name or absolute path.
• args: command-line arguments.
• filetypes: Vim filetypes handled by the server.
• rootPatterns: project marker names.
• priority: optional integer used when multiple servers handle the same filetype. Higher values win; ties are ordered by server name so selection is stable.
• initializationOptions: value sent during LSP initialization.
• settings: values used for configuration notifications and server-initiated workspace/configuration requests.

See simplecc.json.example for all built-in server examples, including Julia settings.

Supported languages

Language	Default server	Managed install	External prerequisite
Rust	rust-analyzer	yes	none
C and C++	clangd	yes	none
Python	pyright-langserver	yes	Node.js and npm
Go	gopls	yes	Go
Lua	lua-language-server	yes	none
Julia	LanguageServer.jl	yes	Julia
TypeScript and JavaScript	typescript-language-server	yes	Node.js and npm

Install TypeScript support through SimpleCC:

:SimpleCCInstall typescript-language-server

List managed servers with :SimpleCCServers. Install one with :SimpleCCInstall {name}. Managed installs may contact GitHub, npm, the Go module proxy, or Julia package registries.

Commands

Lifecycle and configuration

Command	Action
:SimpleCC	Show daemon, project, and server status
:SimpleCCStart	Start and initialize SimpleCC
:SimpleCCStop	Shut down SimpleCC and its servers
:SimpleCCRestart	Restart the daemon
:SimpleCCConfig	Open or create the active configuration
:SimpleCCReloadConfig	Validate configuration and hot-reload server settings
:SimpleCCLog	Open the in-memory SimpleCC log
:SimpleCCInstall [server]	Install a managed language server
:SimpleCCServers	List managed server installation state

Navigation and inspection

Command	Action
:SimpleCCHover	Show hover documentation
:SimpleCCDefinition	Go to definition
:SimpleCCReferences	List references
:SimpleCCImplementation	Go to implementation
:SimpleCCTypeDef	Go to type definition
:SimpleCCOutline	Show document symbols
:SimpleCCWorkspaceSymbol [query]	Search workspace symbols
:SimpleCCWorkspaceSymbolLive	Open live workspace-symbol search
:SimpleCCHighlight	Highlight references under the cursor
:SimpleCCHighlightClear	Clear document highlights
:SimpleCCIncomingCalls	Show incoming calls
:SimpleCCOutgoingCalls	Show outgoing calls
:SimpleCCSupertypes	Show supertypes
:SimpleCCSubtypes	Show subtypes

Editing and language features

Command	Action
:SimpleCCRename	Rename the symbol under the cursor
:SimpleCCFormat	Format the current buffer
:SimpleCCAction	Select a code action
:SimpleCCSignatureHelp	Show signature help
:SimpleCCInlayHints	Toggle inlay hints
:SimpleCCSelExpand	Expand the current selection
:SimpleCCSelShrink	Shrink the current selection
:SimpleCCSemanticTokens	Refresh semantic tokens
:SimpleCCCodeLens	Display code lenses
:SimpleCCCodeLensRun	Execute a code lens
:SimpleCCFold	Apply server-provided folding ranges

Diagnostics and Julia

Command	Action
:SimpleCCDiagnostics	Put diagnostics in the quickfix list
:SimpleCCNextDiag	Jump to the next diagnostic
:SimpleCCPrevDiag	Jump to the previous diagnostic
:SimpleCCPullDiag	Request pull diagnostics
:SimpleCCJuliaActivate [dir]	Activate a Julia environment
:SimpleCCJuliaRefresh	Refresh LanguageServer.jl caches

Default mappings

Set let g:simplecc_no_default_maps = 1 before loading the plugin to disable all default mappings.

Mapping	Action
gd	Definition
gr	References
K	Hover
gi	Implementation
gy	Type definition
<leader>rn	Rename
<leader>ca	Code action
<leader>f	Format
<leader>o	Document outline
<leader>ih	Toggle inlay hints
[d / ]d	Previous / next diagnostic
Insert-mode Tab, Shift-Tab, arrows, Enter	Navigate and accept completion

Options

Set options before plugin/simplecc.vim is loaded.

Option	Default	Purpose
g:simplecc_auto_start	1	Start on VimEnter
g:simplecc_no_default_maps	0	Disable built-in mappings
g:simplecc_config_path	empty	Explicit configuration path
g:simplecc_daemon_path	empty	Explicit daemon executable
g:simplecc_auto_complete	1	Enable automatic completion
g:simplecc_change_delay	120	Document-change debounce in ms
g:simplecc_complete_delay	80	Completion debounce in ms
g:simplecc_complete_min_chars	1	Minimum typed characters
g:simplecc_complete_max_items	100	Maximum completion items
g:simplecc_complete_resolve_delay	120	Resolve debounce in ms
g:simplecc_complete_buffer_words	1	Supplement LSP with keyword matches from open buffers
g:simplecc_complete_buffer_max_items	20	Max buffer-word candidates per menu
g:simplecc_sign_error	E>	Error sign text
g:simplecc_sign_warn	W>	Warning sign text
g:simplecc_sign_info	I>	Information sign text
g:simplecc_sign_hint	H>	Hint sign text
g:simplecc_auto_install	0	Install missing managed servers without prompting
g:simplecc_inlay_hints	1	Enable inlay hints
g:simplecc_virtual_diag	1	Enable virtual diagnostic text
g:simplecc_diag_max_per_line	3	Virtual diagnostics per line
g:simplecc_diag_float

Troubleshooting

Daemon not found

Run ./install.sh, confirm lib/simplecc-daemon is executable, or set g:simplecc_daemon_path to an absolute executable path.

Language server not found

Check the executable directly, for example rust-analyzer --version. Use :SimpleCCInstall for a managed server, then :SimpleCCRestart. Inspect :SimpleCCLog for startup errors.

Configuration does not apply

Validate the JSON and save it. Use :SimpleCCReloadConfig for settings-only changes; use :SimpleCCRestart for server command, arguments, initialization, routing, root-pattern, or priority changes. Check :SimpleCCLog if loading fails. An explicit g:simplecc_config_path takes precedence over discovered files.

No completion or navigation result

Confirm :SimpleCC reports a ready daemon, the current &filetype appears in the server configuration, and the server starts successfully. Use :SimpleCCRestart after changing server executables.

Julia server does not start

Julia