Managing LSPs in Neovim: Enable/Disable for the Entire Session

-- Initialize a flag to toggle LSPs on or off
local lsp_enabled = true
-- Store buffers attached to each LSP client
local attached_buffers_by_client = {}
-- Store configurations for each LSP client
local client_configs = {}

-- Store a reference to the original buf_attach_client function
local original_buf_attach_client = vim.lsp.buf_attach_client

-- Function to add a buffer to the client's buffer table
local function add_buf(client_id, buf)
    if not attached_buffers_by_client[client_id] then
        attached_buffers_by_client[client_id] = {}
    end

    -- Check if the buffer is already in the list
    local exists = false
    for _, value in ipairs(attached_buffers_by_client[client_id]) do
        if value == buf then
            exists = true
            break
        end
    end

    -- Add the buffer if it doesn’t already exist in the client’s list
    if not exists then
        table.insert(attached_buffers_by_client[client_id], buf)
    end
end

-- Middleware function to control LSP client attachment to buffers
-- Prevents LSP client from reattaching if LSPs are disabled
vim.lsp.buf_attach_client = function(bufnr, client_id)
    if not lsp_enabled then
        -- Cache client configuration if not already stored
        if not client_configs[client_id] then
            local client_config = vim.lsp.get_client_by_id(client_id)
            client_configs[client_id] = (client_config and client_config.config) or {}
        end

        -- Add buffer to client’s attached buffer list and stop the client
        add_buf(client_id, bufnr)
        vim.lsp.stop_client(client_id)

        return false                                    -- Indicate the client should not attach
    end
    return original_buf_attach_client(bufnr, client_id) -- Use the original attachment method if enabled LSP
end

-- Update state with new client IDs after a toggle
local function update_clients_ids(ids_map)
    local new_attached_buffers_by_client = {}
    local new_client_configs = {}

    -- Map each client ID to its new ID and carry over configurations
    for client_id, buffers in pairs(attached_buffers_by_client) do
        local new_id = ids_map[client_id]
        new_attached_buffers_by_client[new_id] = buffers
        new_client_configs[new_id] = client_configs[client_id]
    end

    attached_buffers_by_client = new_attached_buffers_by_client -- Update global attached buffer table
    client_configs = new_client_configs                         -- Update global client config table
end

-- Stops the client, waiting up to 5 seconds; force quits if needed
local function client_stop(client)
    vim.lsp.stop_client(client.id, false)

    local timer = vim.uv.new_timer() -- Create a timer
    local max_attempts = 50          -- Set max attempts to check if stopped
    local attempts = 0               -- Track the number of attempts

    timer:start(100, 100, vim.schedule_wrap(function()
        attempts = attempts + 1

        if client.is_stopped() then -- Check if the client is stopped
            timer:stop()
            timer:close()
            vim.diagnostic.reset()               -- Reset diagnostics for the client
        elseif attempts >= max_attempts then     -- If max attempts reached
            vim.lsp.stop_client(client.id, true) -- Force stop the client
            timer:stop()
            timer:close()
            vim.diagnostic.reset() -- Reset diagnostics for the client
        end
    end))
end

-- Toggle LSPs on or off, managing client states and attached buffers
local function toggle_lsp()
    if lsp_enabled then                 -- If LSP is currently enabled, disable it
        client_configs = {}             -- Clear client configurations
        attached_buffers_by_client = {} -- Clear attached buffers

        -- Loop through all active LSP clients
        for _, client in ipairs(vim.lsp.get_clients()) do
            client_configs[client.id] = client.config -- Cache client config

            -- Loop through all buffers attached to the client
            for buf, _ in pairs(client.attached_buffers) do
                add_buf(client.id, buf)                   -- Add buffer to the client’s buffer table
                vim.lsp.buf_detach_client(buf, client.id) -- Detach the client from the buffer
            end

            client_stop(client) -- Stop the client
        end

        print("LSPs Disabled")
    else -- If LSP is currently disabled, enable it
        local new_ids = {}

        -- Reinitialize clients with previous configurations
        for client_id, buffers in pairs(attached_buffers_by_client) do
            local client_config = client_configs[client_id]                -- Retrieve client config
            local new_client_id, err = vim.lsp.start_client(client_config) -- Start client with config

            new_ids[client_id] = new_client_id                             -- Map old client ID to new client ID

            if err then                                                    -- Notify if there was an error starting the client
                vim.notify(err, vim.log.levels.WARN)
                return nil
            end

            -- Reattach buffers to the newly started client
            for _, buf in ipairs(buffers) do
                original_buf_attach_client(buf, new_client_id)
            end
        end

        update_clients_ids(new_ids) -- Update client IDs
        print("LSPs Enabled")       -- Notify that LSPs are enabled
    end

    lsp_enabled = not lsp_enabled -- Toggle the LSP enabled flag
end

-- Set key mapping to toggle LSP on or off with <leader>tl
vim.keymap.set("n", "<leader>tl", toggle_lsp)