luamigemo

日本語

Pure Lua migemo engine for LuaJIT. Converts romaji input into regex patterns that match hiragana, katakana, and kanji — enabling Japanese incremental search without switching input methods.

Ported from oguna/jsmigemo.

Requirements

• LuaJIT (including Neovim's built-in LuaJIT)

A migemo compact dictionary is bundled, so no additional setup is needed.

Usage

local migemo = require "luamigemo"

-- Uses the bundled dictionary and PCRE regex by default
local pattern = migemo.query("kensaku")
-- => PCRE regex matching 検索, けんさく, ケンサク, etc.

Customizing regex dialect or dictionary

Pass an rxop table to query() to change the regex dialect:

local migemo = require "luamigemo"

-- Use Vim regex dialect
local pattern = migemo.query("tokyo", migemo.RXOP_VIM)

Query flags

query() accepts an optional bit-OR-ed flag number as a third argument.

Flag	Description
FLAG_NFD	Emit a regex that matches both NFC (composed) and NFD (decomposed) forms of voiced / semi-voiced kana. Needed when matching filenames returned by macOS APFS / iCloud Drive, which yield NFD-decomposed Japanese filenames.

local migemo = require "luamigemo"

-- Match both NFC "サブ" and NFD "サ + フ + ◌゙" with the same regex
local pattern = migemo.query("sabu", migemo.RXOP_VIM, migemo.FLAG_NFD)

The default path (no flag, or flags == 0) is byte-identical to prior versions. Internal caches are kept separate per flag value, so toggling the flag at runtime does not invalidate already-warmed entries.

Custom dictionary

You can use a different dictionary by passing a path to migemo.get():

local migemo = require "luamigemo"

-- Use a custom dict (e.g., the larger GPL dict from migemo-compact-dict-latest)
local m = migemo.get("/path/to/migemo-compact-dict")
local pattern = m:query("kensaku")

The larger GPL-licensed dictionary is available from oguna/migemo-compact-dict-latest. It is derived from SKK-JISYO.L and has more entries than the bundled BSD dictionary.

Regex dialects

Constant	Description
RXOP_PCRE	PCRE syntax (for ripgrep, etc.)
RXOP_VIM	Vim regex syntax (for vim.regex())

Health check

In Neovim, run :checkhealth luamigemo to verify the dictionary and LuaJIT environment.

Modules

Module	Description
luamigemo	Main API with singleton management
luamigemo.compact_dictionary	Binary dictionary reader (jsmigemo format)
luamigemo.louds_trie	LOUDS-encoded trie
luamigemo.nfd	Canonical NFD decomposition table for kana
luamigemo.bit_vector	Succinct bit vector with rank/select
luamigemo.romaji_processor	Romaji to hiragana with predictive conversion
luamigemo.ternary_regex_generator	Regex pattern builder
luamigemo.character_converter	Full/half-width and hiragana/katakana conversion

Install

As a Neovim plugin dependency (lazy.nvim)

{ "delphinus/luamigemo", version = "*" }

LuaRocks

luarocks install luamigemo

Manual

Clone this repository and add lua/ to your package.path:

git clone https://github.com/delphinus/luamigemo.git

package.path = "/path/to/luamigemo/lua/?.lua;/path/to/luamigemo/lua/?/init.lua;" .. package.path

Dictionary

The bundled dictionary (dict/migemo-compact-dict) is compiled from yet-another-migemo-dict by jsmigemo. It is licensed under the BSD 3-Clause License (see dict/LICENSE).

Tests

Specs live under spec/ and use busted. To run them locally:

luarocks --local install busted
~/.luarocks/bin/busted

Release

Pushing a tag matching v* triggers a GitHub Actions workflow that automatically publishes the package to LuaRocks.

git tag v1.0.0
git push origin v1.0.0

License

MIT License. See LICENSE for details.

Credits

• oguna/jsmigemo — original TypeScript implementation
• oguna/yet-another-migemo-dict — dictionary data (BSD 3-Clause)
• koron/cmigemo — C/Migemo
• migemo — original concept by Satoru Takabayashi