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RustOwl Configuration (Neovim)

docs/neovim-configuration.md

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RustOwl Configuration (Neovim)

Quick Start

  1. Install RustOwl (see docs/installation.md) and the Neovim plugin via your plugin manager.
  2. Add the minimal setup to your lazy.nvim config and open a Rust Cargo workspace.
  3. Hover the cursor over a variable and wait ~500ms to see visualizations.

This document describes all available configuration options for the RustOwl Neovim plugin.

Table of Contents

<!--toc:start-->

Basic Setup

The minimal configuration for RustOwl using lazy.nvim:

lua
{
  'cordx56/rustowl',
  version = '*', -- Latest stable version
  build = 'cargo install rustowl',
  lazy = false, -- This plugin is already lazy
  opts = {},
}

Configuration Options

All configuration options are optional and have sensible defaults:

auto_attach (boolean)

  • Default: true
  • Description: Automatically attach the RustOwl LSP client when opening a Rust file.

auto_enable (boolean)

  • Default: false
  • Description: Enable RustOwl highlighting immediately when the LSP client attaches. When false, you need to manually enable highlighting using :Rustowl enable or require('rustowl').enable().

idle_time (number)

  • Default: 500
  • Description: Time in milliseconds to hover with the cursor before triggering RustOwl analysis and highlighting.

highlight_style (table)

  • Description: The style of underline for different highlight types. 'undercurl' or 'underline'.

colors (table)

  • Description: Custom colors for different highlight types. Each color should be a hex color string (e.g., '#ff0000').

Available Color Options:

  • lifetime: Color for variable lifetime highlights (default: '#00cc00' - green)
  • imm_borrow: Color for immutable borrow highlights (default: '#0000cc' - blue)
  • mut_borrow: Color for mutable borrow highlights (default: '#cc00cc' - purple)
  • move: Color for value move highlights (default: '#cccc00' - yellow)
  • call: Color for function call highlights (default: '#cccc00' - yellow)
  • outlive: Color for lifetime error highlights (default: '#cc0000' - red)

client (table)

  • Description: LSP client configuration that gets passed to vim.lsp.start. This follows the same structure as Neovim's LSP client configuration.

Customizing Highlight Colors

Default Highlight Style

Default highlight style is straight underline except for maybe live and errors.

Default Colors

The default color scheme uses the following colors that correspond to the visual legend:

  • 🟩 Green (#00cc00): Variable's lifetime
  • 🟦 Blue (#0000cc): Immutable borrowing
  • 🟪 Purple (#cc00cc): Mutable borrowing
  • 🟧 Yellow (#cccc00): Value moved / function call
  • 🟥 Red (#cc0000): Lifetime errors

Custom Colors

To customize colors, specify them in the colors table:

lua
opts = {
  colors = {
    lifetime = '#32cd32',   -- Lime green
    imm_borrow = '#4169e1', -- Royal blue
    mut_borrow = '#ff69b4', -- Hot pink
    move = '#ffa500',       -- Orange
    call = '#ffd700',       -- Gold
    outlive = '#dc143c',    -- Crimson
  },
}

Color Format

Colors must be specified as hex color strings:

  • ✅ Valid: '#ff0000', '#00ff00', '#0000ff'
  • ❌ Invalid: 'red', 'rgb(255,0,0)', '#f00'

Partial Color Customization

You can customize only specific colors while keeping the defaults for others:

lua
opts = {
  colors = {
    lifetime = '#90ee90',   -- Light green for better visibility
    outlive = '#ff4500',    -- Orange red for errors
    -- Other colors will use defaults
  },
}

Examples

Example 1: Minimal Configuration

lua
{
  'cordx56/rustowl',
  version = '*',
  build = 'cargo install rustowl',
  lazy = false,
  opts = {},
}

Example 2: Auto-enable with Custom Colors

lua
{
  'cordx56/rustowl',
  version = '*',
  build = 'cargo install rustowl',
  lazy = false,
  opts = {
    auto_enable = true,
    colors = {
      lifetime = '#90ee90',   -- Light green
      imm_borrow = '#87ceeb', -- Sky blue
      mut_borrow = '#dda0dd', -- Plum
      move = '#f0e68c',       -- Khaki
      call = '#ffd700',       -- Gold
      outlive = '#ff6347',    -- Tomato
    },
  },
}

Example 3: Custom Key Binding and Styling

lua
{
  'cordx56/rustowl',
  version = '*',
  build = 'cargo install rustowl',
  lazy = false,
  opts = {
    auto_enable = false,
    idle_time = 300,
    highlight_style = {
      definitely_live = 'underline',
      maybe_initialized = 'undercurl',
    },
    colors = {
      outlive = '#ff0000', -- Bright red for errors
    },
    client = {
      on_attach = function(_, buffer)
        vim.keymap.set('n', '<leader>ro', function()
          require('rustowl').toggle(buffer)
        end, { buffer = buffer, desc = 'Toggle RustOwl' })

        vim.keymap.set('n', '<leader>re', function()
          require('rustowl').enable(buffer)
        end, { buffer = buffer, desc = 'Enable RustOwl' })

        vim.keymap.set('n', '<leader>rd', function()
          require('rustowl').disable(buffer)
        end, { buffer = buffer, desc = 'Disable RustOwl' })
      end
    },
  },
}

Example 4: Dark Theme Optimized Colors

lua
{
  'cordx56/rustowl',
  version = '*',
  build = 'cargo install rustowl',
  lazy = false,
  opts = {
    colors = {
      lifetime = '#50fa7b',   -- Dracula green
      imm_borrow = '#8be9fd', -- Dracula cyan
      mut_borrow = '#ff79c6', -- Dracula pink
      move = '#f1fa8c',       -- Dracula yellow
      call = '#ffb86c',       -- Dracula orange
      outlive = '#ff5555',    -- Dracula red
    },
  },
}

Example 5: For init.vim Users

If you're using init.vim instead of init.lua, you can configure RustOwl using Vim script:

vim
lua << EOF
require('lazy').setup({
  {
    'cordx56/rustowl',
    version = '*',
    build = 'cargo install rustowl',
    lazy = false,
    opts = {
      colors = {
        lifetime = '#00ff00',
        imm_borrow = '#0080ff',
        mut_borrow = '#ff00ff',
        move = '#ffff00',
        call = '#ffa500',
        outlive = '#ff0000',
      },
    },
  },
})
EOF

Usage Commands

When opening a Rust file, the following commands become available:

  • :Rustowl start_client - Start the RustOwl LSP client
  • :Rustowl stop_client - Stop the RustOwl LSP client
  • :Rustowl restart_client - Restart the RustOwl LSP client
  • :Rustowl enable - Enable RustOwl highlighting
  • :Rustowl disable - Disable RustOwl highlighting
  • :Rustowl toggle - Toggle RustOwl highlighting

You can also use the Lua API:

lua
require('rustowl').enable()   -- Enable highlighting
require('rustowl').disable()  -- Disable highlighting
require('rustowl').toggle()   -- Toggle highlighting
require('rustowl').is_enabled() -- Check if enabled