NeoViM: Improve Telescope (last edited) find files

Sometimes ago I have stated I was using ViM.

After Bram Moolenaar's death, ViM's future was changed and I could not hope for Tree-sitter integration anymore, so, after a while, I have decided to move to NeoViM.

I usually reflect on my workflow early in the morning, before the breakfast, one of the thing I have noticed, using Telescope to find/open files, is my tendency to re-open the same files over and over during a coding session.

For example, I open A.hs to mainly work on it, then temporarily open B.hs to check or change something, close it, keep working on A.hs, then open C.hs change something, close it, keep working on A.hs, re-open B.hs, etc.

I have tried telescope-recent-files / telescope-all-recent, but they were too limited (displaying only recent files), or heavy (requiring SQLite), so I have decided to come up with my own solution.

To build a Telescope you need few things:

• A picker which is the input list (e.g. files, lines, history, git commits, etc.)
• A sorter to arrange results for the picker
• Eventually a previewer to print something in the panel

Let's start with the configuration:

require('telescope').setup {
    defaults = {
        file_sorter = opened_files_sorter,
    },
}

A Sorter is actually an object:

local function opened_files_sorter(opts)
    opts = opts or {}

    local sorters = require("telescope.sorters")

    local fuzzy_sorter = sorters.get_fzy_sorter(opts)

    return sorters.new {
        scoring_function = function(_, prompt, line, entry, cb_add, cb_filter)
            -- here will be the logic
        end,
        highlighter = fuzzy_sorter.highlighter,
    }
end

A Sorter is composed by:

• A scoring function which mainly takes the prompt (what we are looking for), the line and the entry we are trying to sort (provided by the picker)
• A highlighting function

I have decided to take de builtin fuzzer sorter as basis.

Let's rely on it as first implementation:

local function opened_files_sorter(opts)
    opts = opts or {}

    local sorters = require("telescope.sorters")

    local fuzzy_sorter = sorters.get_fzy_sorter(opts)

    return sorters.new {
        scoring_function = function(_, prompt, line, entry, cb_add, cb_filter)
            local FILTERED = -1
            local filepath = vim.fn.resolve(vim.fn.getcwd() .. '/' .. entry.value)

            local base_score = fuzzy_sorter:scoring_function(prompt, line, entry, cb_add, cb_filter)
            if base_score == FILTERED then
                return FILTERED
            end

            return base_score
            end
        end,
        highlighter = fuzzy_sorter.highlighter,
    }
end

Then we should collect opened files:

local opened_files_since_start = {}
local function update_opened_files()
    local current_file = vim.fn.expand('%:p')
    opened_files_since_start[current_file] = true
end

-- In config
local autocmd = vim.api.nvim_create_autocmd
autocmd('BufReadPost', {
    pattern = '',
    callback = update_opened_files
})

so we can change the score regarding opened files:

local function opened_files_sorter(opts)
    opts = opts or {}

    local sorters = require("telescope.sorters")

    local fuzzy_sorter = sorters.get_fzy_sorter(opts)

    return sorters.new {
        scoring_function = function(_, prompt, line, entry, cb_add, cb_filter)
            local FILTERED = -1
            local filepath = vim.fn.resolve(vim.fn.getcwd() .. '/' .. entry.value)

            local base_score = fuzzy_sorter:scoring_function(prompt, line, entry, cb_add, cb_filter)
            if base_score == FILTERED then
                return FILTERED
            end

            if opened_files_since_start[filepath] then
                return 0.001 * base_score
            else
                return base_score
            end
        end,
        highlighter = fuzzy_sorter.highlighter,
    }
end

So far so good, to limit the results, I want to filter-out the currently opened files:

local function opened_files_sorter(opts)
    opts = opts or {}

    local sorters = require("telescope.sorters")

    local fuzzy_sorter = sorters.get_fzy_sorter(opts)

    return sorters.new {
        scoring_function = function(_, prompt, line, entry, cb_add, cb_filter)
            local FILTERED = -1
            local filepath = vim.fn.resolve(vim.fn.getcwd() .. '/' .. entry.value)

            for _, buf in ipairs(vim.fn.getbufinfo({ buflisted = 1 })) do
                if buf.windows and #buf.windows > 0 and buf.name == filepath then
                    return FILTERED
                end
            end

            local base_score = fuzzy_sorter:scoring_function(prompt, line, entry, cb_add, cb_filter)
            if base_score == FILTERED then
                return FILTERED
            end

            if opened_files_since_start[filepath] then
                return 0.001 * base_score
            else
                return base_score
            end
        end,
        highlighter = fuzzy_sorter.highlighter,
    }
end

And finally, I want to get rid of binary files (i.e. file extensions already listed in wildignore):

local function opened_files_sorter(opts)
    opts = opts or {}

    local sorters = require("telescope.sorters")

    local fuzzy_sorter = sorters.get_fzy_sorter(opts)

    return sorters.new {
        scoring_function = function(_, prompt, line, entry, cb_add, cb_filter)
            local FILTERED = -1
            local filepath = vim.fn.resolve(vim.fn.getcwd() .. '/' .. entry.value)

            for _, buf in ipairs(vim.fn.getbufinfo({ buflisted = 1 })) do
                if buf.windows and #buf.windows > 0 and buf.name == filepath then
                    return FILTERED
                end
            end

            for _, pat in ipairs(vim.split(vim.o.wildignore, ',')) do
                if match_glob(pat, filepath) then
                    return FILTERED
                end
            end

            local base_score = fuzzy_sorter:scoring_function(prompt, line, entry, cb_add, cb_filter)
            if base_score == FILTERED then
                return FILTERED
            end

            if opened_files_since_start[filepath] then
                return 0.001 * base_score
            else
                return base_score
            end
        end,
        highlighter = fuzzy_sorter.highlighter,
    }
end