ballerina.nvim

Ballerina support for Neovim — syntax highlighting, LSP, format-on-save, auto-indent, and bal run/test/build, in one plugin.

Features · Requirements · Installation · Quick start · Commands · Configuration · Debugging · Troubleshooting · Grammar notes · Roadmap · Related · Contributing · License

Why not just nvim-lspconfig? LSP is only one part of what this plugin does — package-aware format-on-save, a brace-aware indentexpr, :Ballerina{Run,Test,Build} with quickfix integration, and DAP debugging all ship alongside the LSP config, so swapping in nvim-lspconfig for the LSP piece alone still leaves those out. (If you already use nvim-lspconfig, it's not a conflict either way — see LSP capabilities under Configuration.)

Features

• Syntax highlighting matching the Ballerina compiler's keyword/type lists (details)
• LSP via a native vim.lsp.config definition — hover, completion, rename, code actions, diagnostics, the works
• Format on save, package-aware (bal format can't format a single file that belongs to a package, so the plugin formats the whole package and reloads affected buffers)
• Auto-indent — a brace/paren-aware indentexpr (cindent misreads io:println(...) as a C jump label)
• :Ballerina{Run,Test,Build,Format} commands, with compiler diagnostics landing in the quickfix list
• Debugging via nvim-dap, auto-registered if it's installed
• :checkhealth ballerina

Requirements

• Neovim >= 0.11
• The Ballerina distribution — ballerina.io/downloads or brew install ballerina (bundles its own JVM, no separate JDK needed). Developed against Swan Lake 2201.13.x.
• bal on your PATH. If it isn't (common when GUI Neovim is launched outside a login shell), the plugin also checks $BALLERINA_HOME and the official installer locations — see Setting the Ballerina distribution.

Installation

lazy.nvim:

{
  "redpierrot/ballerina.nvim",
  ft = "ballerina",
  opts = {},
}

Published on LuaRocks — also installable with rocks.nvim:

:Rocks install ballerina.nvim

vim-plug / native packages

Plug 'redpierrot/ballerina.nvim'

-- after plug#end():
require("ballerina").setup({})

Or with Neovim's built-in package support (:h packages):

git clone https://github.com/redpierrot/ballerina.nvim \
  ~/.local/share/nvim/site/pack/plugins/start/ballerina.nvim

Calling setup() is optional — the plugin works with its defaults as soon as a .bal file is opened. Call it only to override options.

Quick start

Open a .bal file. You get indentation, syntax highlighting, and the language server attaches automatically (first start takes a few seconds while the JVM warms up — watch :checkhealth vim.lsp).

Neovim's default LSP mappings work out of the box: K hover, grn rename, gra code action, grr references, gO document symbols, [d/]d diagnostics.

Commands

Command	Action
:BallerinaFormat	Format the file (or its enclosing package) now
:BallerinaFormatToggle	Toggle format-on-save for this buffer
:BallerinaRun [args]	bal run the package/script in a terminal split
:BallerinaTest [args]	bal test in a terminal split
:BallerinaBuild [args]	bal build in a terminal split

Run/Test/Build accept arguments: everything before a literal -- is a CLI option (before the target), everything after is a program argument (after the target) — matching bal run [options] [target] [-- program-args]:

:BallerinaTest --tests fooTest
:BallerinaRun -- 8080 --verbose

Compiler diagnostics and bal test assertion failures both land in the quickfix list — the quickfix window opens automatically once you close the terminal split (it won't pop up over output you're still reading). Prefer :make? :compiler ballerina sets the same makeprg/errorformat.

Saving a file runs bal format in the background. To turn that off for one buffer, use :BallerinaFormatToggle (or set vim.b.ballerina_disable_format = true); to turn it off everywhere, set format_on_save = false.

Configuration

Defaults:

require("ballerina").setup({
  bal_cmd = nil,   -- path to the `bal` binary; nil = auto-detect
  bal_home = nil,  -- path to a distribution root; nil = auto-detect
  format_on_save = true,
  indent = true,
  lsp = {
    enabled = true,
    root_markers = { "Ballerina.toml" },
    file_watch = true,  -- see Troubleshooting if you hit a watcher crash
    config = nil,       -- extra vim.lsp.Config fields, e.g. capabilities
  },
  dap = {
    enabled = true,
  },
})

Setting the Ballerina distribution

By default the plugin resolves bal from your PATH, then $BALLERINA_HOME/bin/bal, then the official installer locations. :checkhealth ballerina always shows which one it picked.

Override it with either:

• bal_home — a distribution root (the $BALLERINA_HOME layout, with bin/bal inside). Handy for pointing at a locally built distribution.
• bal_cmd — an exact binary path. Wins over bal_home if both are set.

Globally, in every project:

require("ballerina").setup({
  bal_home = "~/ballerina-lang/distribution/zip/jballerina-tools/build/"
    .. "extracted-distributions/jballerina-tools-<version>",
})

Per-project — e.g. trying a local ballerina-lang build against one repo without touching your global config — pick one:

• A project-local .nvim.lua (Neovim's exrc, see :h exrc) that calls setup() with a different bal_home. Requires vim.o.exrc = true and trusting the file once (:h :trust).
• $BALLERINA_HOME set per-directory, e.g. via direnv — already in the auto-detect chain, so it works automatically as long as bal_home/bal_cmd aren't also set globally (explicit config always wins over the env var).

LSP capabilities

To pass completion capabilities from blink.cmp or nvim-cmp:

require("ballerina").setup({
  lsp = {
    config = {
      capabilities = require("blink.cmp").get_lsp_capabilities(),
      -- capabilities = require("cmp_nvim_lsp").default_capabilities(),
    },
  },
})

Or, since the server is a native vim.lsp.config definition, set it directly without going through setup():

vim.lsp.config("ballerina", {
  capabilities = require("blink.cmp").get_lsp_capabilities(),
})

Using nvim-lspconfig?

nvim-lspconfig ships an equivalent ballerina definition. That's fine: Neovim merges same-named lsp/ definitions, and anything set via vim.lsp.config("ballerina", ...) wins over both. You will not get two clients.

Debugging

With nvim-dap installed, opening a .bal file registers the Ballerina debug adapter (the same bal start-debugger-adapter the VS Code extension uses) plus four configurations:

• Debug Ballerina program — debug the current package/script
• Debug Ballerina program (prompt for arguments)
• Debug Ballerina tests — bal test under the debugger
• Attach to running program — for processes started with bal run --debug <port>

Set a breakpoint and :lua require("dap").continue() (or your usual dap keymaps). No launch.json needed. The first launch takes several seconds — the adapter and the debuggee are JVM processes.

Troubleshooting

• Run :checkhealth ballerina first — it verifies the Neovim version, locates bal (and prints which one), and reports the LSP client state.
• Language server not attaching? Almost always bal missing from the environment Neovim was launched in — see Setting the Ballerina distribution.
• :checkhealth vim.lsp shows the client log if the server starts and then crashes.

Neovim crashes with ENAMETOOLONG from vim._watch

[!WARNING] Neovim can crash on macOS when LSP file-watching hits a pathologically long build-cache path. This plugin scopes what it watches to work around it, but see the workaround below if it still happens to you.

Mentioning a path under a compiler/Gradle build cache (target/, .gradle/, ...): a known Neovim limitation on macOS, where LSP workspace file watching uses a single recursive fs_event over the whole project by default. It has no way to exclude subdirectories at the OS level, so if a build ever produces a pathologically long or invalid path there (observed with JaCoCo code-coverage instrumentation in Gradle-wrapped builds), Neovim asserts and crashes outright — before the change even reaches this plugin's LSP client.

This plugin works around it by scoping what gets watched to Ballerina's own package structure (Ballerina.toml, loose .bal files, modules/, generated/) instead of the whole workspace folder, so a build cache is never watched, recursively or otherwise — see lua/ballerina/lsp_watch.lua and docs/proposals/scoped-lsp-file-watch.md for the mechanism.

Even the package root's own non-recursive watch isn't fully immune: under a heavy write burst inside a build-cache directory (JaCoCo instrumenting hundreds of classes during bal test --code-coverage is the observed trigger), a stray event can still surface a pathologically long path from deep inside target/, and core's vim._watch.watch asserts and crashes on that unconditionally. This plugin's root watcher uses its own fs_event wrapper instead of calling into core's, so that specific assert can no longer bring Neovim down.

If you hit a crash anyway (e.g. a Ballerina LS version that registers watch patterns this plugin doesn't recognize — it warns loudly when that happens), set lsp.file_watch = false as a full opt-out. The tradeoff: the server no longer auto-discovers files it didn't get through Neovim (git checkouts/pulls, .bal source generated by bal openapi/grpc/etc. run outside Neovim) — open or re-save the generated file, or :LspRestart, to pick those up.

Grammar notes

Why not the official TextMate grammar?

The official grammar (ballerina.YAML-tmLanguage) is a TextMate grammar consumed by the VS Code extension, forked from the same scaffold used for TypeScript's grammar. Most of its complexity is generic disambiguation machinery (arrow functions vs. comparisons vs. generics) that doesn't reflect anything Ballerina-specific and can't be expressed in Vim's regex engine (no recursive patterns). Rather than attempt a byte-for-byte port, this plugin takes the authoritative keyword/type lists from the compiler's LexerTerminals.java (plus parser-level contextual keywords like group and collect) and implements conventional :syntax keyword/:syntax match/:syntax region rules around them — the same level of coverage most language syntax files have.

Roadmap

• neotest adapter for bal test
• Snippets
• Treesitter support, if/when a Ballerina grammar appears

Related

• blink.cmp / nvim-cmp — completion sources, see LSP capabilities
• neotest — test runner UI; a bal test adapter is planned, see Roadmap
• nvim-dap — debugging front-end, see Debugging

Contributing

See CONTRIBUTING.md. In short: make test, make lint, make fmt — CI runs the same checks.

License

MIT