dexter-lsp

Dexter

A fast, full-featured Elixir LSP optimized for large Elixir codebases.

Table of contents

• Features
• Quick start
• Editor setup
  • VS Code / Cursor
    • Configuration
  • Neovim (0.11+)
    • Configuring format on save
  • Neovim (with nvim-lspconfig — < 0.11)
  • Zed
  • Claude Code
  • Emacs
    • Eglot
      • Emacs version >= 30
      • Emacs version <= 29
    • lsp-mode
  • Helix
• Why build another LSP?
• Performance
• CLI usage
  • Index a project
  • Look up definitions
  • Find references
  • Reindexing files manually
• Hover documentation
  • Cursor-position-aware resolution
• Rename
  • Modules
  • Functions
  • Variables
• Lightning-fast formatting
• LSP options
• Index database location (.dexter/)
• Debugging
• Development (building from source)
• Releasing
• Contributing
• License

Features

• Fast indexing — cold index completes in ~11s on a 57k-file Elixir monorepo, ~100ms on Oban, ~300ms on the Elixir standard library (measured on an M1 MacBook Pro). After your first index, incremental indexing makes sure that you never have to reindex the whole codebase again.
• Go-to-definition — jump to any module, function, type, or variable definition. Resolves aliases, imports, defdelegate chains, use injections, and the Elixir stdlib. Handles all definition forms: def, defp, defmacro, defprotocol, defimpl, defstruct, and more.
• Go-to-references — find all usages of a function or module across the codebase, including through import, use chains, and defdelegate.
• Hover documentation — @doc, @moduledoc, @typedoc, and @spec annotations rendered as Markdown when you hover over a symbol.
• Autocompletion — modules, functions, types, and variables with full snippet support. Resolves through aliases, imports, use injections, and the Elixir stdlib. Works for qualified calls (MyApp.Accounts.|), bare function calls, and module prefixes.
• Rename — rename modules, functions, and variables with automatic file renaming when the convention is followed.
• No compilation required — the index is built by parsing source files directly, not by compiling your project. Dexter works immediately on any codebase, even ones that don't compile.
• Monorepo and umbrella support — a single index at the repository root covers all apps and shared libraries. Go-to-definition, find references, and rename work cross-project out of the box.
• Format on save — formats .ex, .exs, and .heex files on save via a persistent Elixir process. Near-instant after the first save. Formatter plugins (Styler, Phoenix.LiveView.HTMLFormatter) are loaded from your project's _build — no install needed. Syntax errors are surfaced as diagnostics.
• Elixir stdlib indexing — jump to Enum, String, Mix, and other bundled modules by indexing your local Elixir installation sources.
• Signature help — parameter hints as you type function calls.
• Workspace symbols — search for any module or function across the entire codebase.
• Call hierarchy — navigate incoming and outgoing calls.
• Code actions — add missing aliases with a single action.
• Document symbols — outline view of all functions and modules in the current file.
• Document highlight — highlight all occurrences of the symbol under the cursor.
• Variable support — go-to-definition, rename, and completion for local variables via tree-sitter, with correct scoping across case, with, for, and other block constructs.
• Git branch switch detection — automatically reindexes when you switch branches.