Neovim

Neovim talks to the same fallow-lsp language server that powers the VS Code extension, through Neovim's built-in LSP client. The setup is intentionally thin: it launches the existing binary instead of re-implementing any analysis in the editor, so results match the CLI and CI exactly.

What works

• Real-time diagnostics for unused files, exports, types, dependencies, enum and class members, unresolved imports, unlisted dependencies, duplicate exports, circular dependencies, and code duplication
• Opt-in security candidate diagnostics when you raise the security-sink or security-client-server-leak rule to warn or error in your fallow config. Candidates surface as advisory information squiggles (unverified, verify before acting); the hover leads with the confidence signals and points to fallow security --file for the full trace, and a quick-fix dismisses the candidate. Default off, so squiggles appear only after you raise the rule.
• Hover information with export usage counts, unused status, and duplicate block locations
• Quick-fix code actions to remove unused exports or delete unused files
• Code lens with export reference counts, where Neovim surfaces them

Installation

1. 1

   Install Fallow so fallow-lsp is on your PATH

   npm install -g fallow

   Or add it as a project devDependency (npm install -D fallow) and point cmd at node_modules/.bin/fallow-lsp.

2. 2

   Confirm Neovim can see the binary

   fallow-lsp --version

3. 3

   Register and enable the server

   Add the configuration below to your Neovim config, then open a TypeScript or JavaScript project.

Configuration

vim.lsp.config("fallow", {
	cmd = { "fallow-lsp" },
	filetypes = { "javascript", "typescript", "javascriptreact", "typescriptreact" },
	root_markers = { ".fallowrc.json", "package.json", ".git" },
	init_options = {
		-- Every issue type is enabled by default. List only the ones you
		-- want to turn off; any key you omit stays enabled.
		issueTypes = {
			["circular-dependencies"] = false,
		},
	},
})

vim.lsp.enable("fallow")

init_options is optional; cmd, filetypes, and root_markers alone are enough to attach.

Issue-type toggles

Fallow reads per-issue toggles from LSP initialization options. Set an issue type to false to hide it in editor diagnostics without touching your project config. The keys are Fallow's issue types in kebab-case (unused-exports, unresolved-imports, circular-dependencies, and so on); a client can fetch the live catalog through the custom fallow/issueTypes request to stay in sync.

Scope to changed files

Pass a git ref as changedSince to scope diagnostics to files changed since that ref, mirroring fallow dead-code --changed-since. This is the Neovim equivalent of the VS Code fallow.changedSince setting, useful for adopting fallow on a legacy codebase without surfacing every pre-existing finding:

init_options = {
	changedSince = "fallow-baseline",
},

Binary resolution

Neovim runs cmd exactly as configured. If fallow-lsp is not on Neovim's PATH, point cmd at an absolute path:

vim.lsp.config("fallow", {
	cmd = { "/absolute/path/to/fallow-lsp" },
	filetypes = { "javascript", "typescript", "javascriptreact", "typescriptreact" },
	root_markers = { ".fallowrc.json", "package.json", ".git" },
})

Verifying the setup

1. Open a TypeScript or JavaScript project.

2. Run :checkhealth vim.lsp.

3. Confirm fallow is attached:

   :lua vim.print(vim.lsp.get_clients({ name = "fallow" }))

See also