Dumb automatic fast indentation detection for Neovim written in Lua

Instead of trying to be smart about detecting an indentation using statistics, it will find the first thing that looks like a standard indentation (tab or 8/4/2 spaces) and assume that's what the file's indentation is

This has the advantage of being fast and very often correct while being simple enough that most people will understand what it will do predictably

• Neovim >= 0.4.4

Can be installed through any standard Vim package manager, configuration is optional

E.g. through vim-plug:

call plug#begin()
    Plug 'Darazaki/indent-o-matic'
call plug#end()

Then restart Neovim and run :PlugInstall

Configuration is done in Lua:

require('indent-o-matic').setup {
    -- The values indicated here are the defaults

    -- Number of lines without indentation before giving up (use -1 for infinite)
    max_lines = 2048,

    -- Space indentations that should be detected
    standard_widths = { 2, 4, 8 },

    -- Skip multi-line comments and strings (more accurate detection but less performant)
    skip_multiline = true,
}

You can also directly configure it from a Vim file by using the lua instruction:

lua <<EOF
require('indent-o-matic').setup {
    -- ...
}
EOF

Optionally you can define language-specific settings using the filetype_$ft tables:

require('indent-o-matic').setup {
    -- Global settings (optional, used as fallback)
    max_lines = 2048,
    standard_widths = { 2, 4, 8 },

    -- Disable indent-o-matic for LISP files
    filetype_lisp = {
        max_lines = 0,
    },

    -- Only detect 4 spaces and tabs for Rust files
    filetype_rust = {
        standard_widths = { 4 },
    },

    -- Don't detect 8 spaces indentations inside files without a filetype
    filetype_ = {
        standard_widths = { 2, 4 },
    },
}

If a preference hasn't been set in the language-specific settings, it'll be retrieved from the global settings

:IndentOMatic is also made available to detect the current buffer's indentation on demand

If you want this plugin to only be invoked manually through :IndentOMatic, you can add autocmd! indent_o_matic to your init file

• guess-indent.nvim by Nicolas Camenisch: Smarter algorithm, configuration similar to indent-o-matic (see explanations/benchmarks)
• crazy8.nvim by zsugabubus: Smarter algorithm
• DetectIndent by Ciaran McCreesh: Manually ran, smarter algorithm, Vim compatible
• vim-sleuth by Tim Pope: Even smarter, Vim compatible

I've made this little plugin as a fun side-project to learn how Lua works with Neovim as a beginner so, if you've an idea, feel free to write a PR to improve this project!

The only rules to follow are:

• PRs should go to the testing branch (for, well, testing if everything still works)
• The detection algorithm should stay dumb
• The plugin itself should work with Lua & Vim code only
• No configuration required
• System requirements shouldn't be restricted
• Break the rules within reason

Note: Forking or taking part of the code without asking is also a-ok, this is libre MIT-licensed stuff!