:help lib.nvim-treesitter

*lib.nvim-treesitter.txt*     Filetype allowlist gate + parser install policy

lib.nvim.treesitter                                    *lib.nvim-treesitter*

Two independent submodules for treesitter-dependent features:

  - guard         filetype allowlist gate (highlighting, foldexpr,
                     indentexpr) — see |lib.nvim-treesitter-guard|
  - parser_policy prompt-or-auto-install policy for missing-but-available
                     parsers — see |lib.nvim-treesitter-parser_policy|

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CONTENTS *lib.nvim-treesitter-contents*

  1. Guard ................................. |lib.nvim-treesitter-guard|
       Usage .............................. |lib.nvim-treesitter-guard-usage|
       Functions .......................... |lib.nvim-treesitter-guard-functions|
         is_enabled ....................... |lib.nvim-treesitter-is_enabled|
  2. Parser Policy .......................... |lib.nvim-treesitter-parser_policy|
       Usage .............................. |lib.nvim-treesitter-parser_policy-usage|
       Modes .............................. |lib.nvim-treesitter-parser_policy-modes|
       Functions .......................... |lib.nvim-treesitter-parser_policy-functions|
         setup ............................ |lib.nvim-treesitter-parser_policy-setup|
         get_mode ......................... |lib.nvim-treesitter-parser_policy-get_mode|
         set_mode ......................... |lib.nvim-treesitter-parser_policy-set_mode|
         declined ......................... |lib.nvim-treesitter-parser_policy-declined|
         reset_declined ................... |lib.nvim-treesitter-parser_policy-reset_declined|
         ensure ........................... |lib.nvim-treesitter-parser_policy-ensure|

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1. GUARD *lib.nvim-treesitter-guard*

Filetype allowlist gate for treesitter-dependent features (highlighting,
foldexpr, indentexpr). Not a parser-availability probe — a curated allowlist
of filetypes considered safe/desired for treesitter activation, kept
centrally so multiple activation hooks share one list.

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USAGE *lib.nvim-treesitter-guard-usage*

    local guard = require("lib.nvim.treesitter.guard")

    vim.api.nvim_create_autocmd("FileType", {
      callback = function(args)
        if guard.is_enabled(args.buf) then
          vim.treesitter.start(args.buf)
        end
      end,
    })

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FUNCTIONS *lib.nvim-treesitter-guard-functions*

is_enabled({bufnr}, {whitelist})            *lib.nvim-treesitter-is_enabled*

Whether treesitter should be enabled for bufnr. whitelist defaults to
guard.DEFAULT_WHITELIST (table<string, boolean>, keyed by filetype).

    guard.is_enabled(bufnr)
    guard.is_enabled(bufnr, { lua = true, python = true })

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2. PARSER POLICY *lib.nvim-treesitter-parser_policy*

Prompt-or-auto-install policy for missing-but-available treesitter parsers.
The modern nvim-treesitter (main branch) never auto-installs anything —
without a mechanism like this, a missing parser degrades silently to no
highlighting at all, with no error anywhere (this is how ---@module
LuaCATS annotations went unhighlighted for a while: the luadoc injection
parser was simply never installed).

This module never calls |vim.treesitter.start()| itself. Callers pass
opts.on_installed to ensure() and decide what "the parser just became
available" means for their buffer(s).

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USAGE *lib.nvim-treesitter-parser_policy-usage*

    local policy = require("lib.nvim.treesitter.parser_policy")
    policy.setup({ mode = "prompt" })

    vim.api.nvim_create_autocmd("FileType", {
      callback = function(args)
        local lang = vim.treesitter.language.get_lang(vim.bo[args.buf].filetype)
        policy.ensure(lang, {
          on_installed = function()
            pcall(vim.treesitter.start, args.buf)
          end,
        })
      end,
    })

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MODES *lib.nvim-treesitter-parser_policy-modes*

"off"       Do nothing.
"prompt"    (default) Ask once per language via a themed select prompt
            (|lib.nvim-kit|): Yes / No / Never for this language.
"auto"      Install immediately, no prompt — just a short notify.

A "Never for <lang>" answer is remembered via lib.nvim.cache (disk
backend) and survives restarts, so the same language never re-prompts.
"No" is not remembered — it asks again next time.

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FUNCTIONS *lib.nvim-treesitter-parser_policy-functions*

setup({opts})                     *lib.nvim-treesitter-parser_policy-setup*

opts.mode sets the initial mode (default "prompt").

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get_mode() *lib.nvim-treesitter-parser_policy-get_mode*

Returns the current mode ("off"|"prompt"|"auto").

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set_mode({mode}) *lib.nvim-treesitter-parser_policy-set_mode*

Switch mode at runtime. Returns ok, err?.

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declined() *lib.nvim-treesitter-parser_policy-declined*

Sorted string[] of languages the user said "never" to.

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reset_declined() *lib.nvim-treesitter-parser_policy-reset_declined*

Clears the declined list, in memory and on disk.

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ensure({lang}, {opts}) *lib.nvim-treesitter-parser_policy-ensure*

Runs the policy for lang. No-op if lang is empty, already installed, not
a known installable parser, mid-install/mid-prompt already, or (in
"prompt" mode) declined. opts.on_installed(lang) fires once, only on a
real successful install.

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