Bacon-ls is a language server implementation specifically designed to work with Bacon projects, exposing textDocument/diagnostic and workspace/diagnostic capabilities to editors.

NOTE: Bacon-ls requires Bacon 3.7+ to work properly.

NOTE: Bacon-ls is not part of Bacon, it's a third-party tool developed to work WITH Bacon.

Features

• Read diagnostics from produced by Bacon.
• Push diagnostics to the LSP client on certain events like saving or files changes.
• Precise diagnostics positions.
• Ability to react to changes over document saves and changes that can be configured.
• Replacement code actions as suggested by clippy.
• Automatic validation of bacon preferences to ensure bacon-ls can work with them.

Installation

VSCode

First, install Bacon.

The VSCode extension is available on both VSCE and OVSX:

• VSCE https://marketplace.visualstudio.com/items?itemName=MatteoBigoi.bacon-ls-vscode
• OVSX https://open-vsx.org/extension/MatteoBigoi/bacon-ls-vscode

Mason.nvim

Both Bacon and Bacon-ls are installable via mason.nvim:

:MasonInstall bacon bacon-ls

Manual

First, install Bacon and Bacon-ls

❯❯❯ cargo install --locked bacon bacon-ls
❯❯❯ bacon --version
bacon 3.7.0  # make sure you have at least 3.7.0
❯❯❯ bacon-ls --version
0.9.0        # make sure you have at least 0.9.0

Configuration

Configure Bacon export settings with bacon-ls 🐽 export format and proper span support in the bacon preference file. To find where the file should be saved, you can use the command bacon --prefs:

[jobs.bacon-ls]
command = [ "cargo", "clippy", "--tests", "--all-targets", "--all-features", "--message-format", "json-diagnostic-rendered-ansi" ]
analyzer = "cargo_json"
need_stdout = true

[exports.cargo-json-spans]
auto = true
exporter = "analyzer"
line_format = "{diagnostic.level}|:|{span.file_name}|:|{span.line_start}|:|{span.line_end}|:|{span.column_start}|:|{span.column_end}|:|{diagnostic.message}|:|{span.suggested_replacement}"
path = ".bacon-locations"

NOTE: Bacon MUST be running to generate the export locations with the Bacon-ls job: bacon -j bacon-ls.

The language server can be configured using the appropriate LSP protocol and supports the following values:

• locationsFile Bacon export filename (default: .bacon-locations).
• updateOnSave Try to update diagnostics every time the file is saved (default: true).
• updateOnSaveWaitMillis How many milliseconds to wait before updating diagnostics after a save (default: 1000).
• updateOnChange Try to update diagnostics every time the file changes (default: true).

Neovim - LazyVim

Bacon-ls is already integrated with LazyVim with PR #3112:

vim.g.lazyvim_rust_diagnostics = "bacon-ls"

Neovim - Manual

NeoVim requires nvim-lspconfig to be configured and rust-analyzer diagnostics must be turned off for Bacon-ls to properly function.

Bacon-ls is part of nvim-lspconfig from commit 6d2ae9f and it can be configured like any other LSP server works best when vim.diagnostics.opts.update_in_insert is set to true.

require("lspconfig").bacon_ls.setup({
    init_options = {
        updateOnSave = true
        updateOnSaveWaitMillis = 1000
        updateOnChange = false
    }
})

For rust-analyzer, these 2 options must be turned off:

rust-analyzer.checkOnSave.enable = false
rust-analyzer.diagnostics.enable = false

VSCode

The extension can be configured using the VSCode settings interface.

It is very important that rust-analyzer Check On Save and Diagnostics are disabled for bacon-ls to work properly:

• Untick Rust-analyzer -> general -> Check On Save
• Untick Rust-analyzer -> diagnostics -> Enable

Coc.nvim

call coc#config('languageserver', {
      \ 'bacon-ls': {
      \   'command': '~/.cargo/bin/bacon-ls',
      \   'filetypes': ['rust'],
      \   'rootPatterns': ['.git/', 'Cargo.lock', 'Cargo.toml'],
      \   'initializationOptions': {
      \     'updateOnSave': v:true,
      \     'updateOnSaveWaitMillis': 1000,
      \     'updateOnChange': v:false
      \   },
      \   'settings': {}
      \ }
\ })

Troubleshooting

Bacon-ls can produce a log file in the folder where its running by exporting the RUST_LOG variable in the shell:

Vim / Neovim

❯❯❯ export RUST_LOG=debug
❯❯❯ nvim src/some-file.rs                 # or vim src/some-file.rs
# the variable can also be exported for the current command and not for the whole shell
❯❯❯ RUST_LOG=debug nvim src/some-file.rs  # or RUST_LOG=debug vim src/some-file.rs
❯❯❯ tail -F ./bacon-ls.log

VSCode

Enable debug logging in the extension options.

❯❯❯ tail -F ./bacon-ls.log

How does it work?

Bacon-ls reads the diagnostics location list generated by Bacon's export-locations and exposes them on STDIO over the LSP protocol to be consumed by the client diagnostics.

It requires Bacon to be running alongside to ensure regular updates of the export locations.

The LSP client reads them as response to textDocument/diagnostic and workspace/diagnostic.

More info

Please visit https://github.com/crisidev/bacon-ls for more information.