Troubleshooting Mini.completion Failed Info Window Display

by StackCamp Team 59 views

#mini.completion can greatly enhance your Neovim experience by providing intelligent code completion suggestions. However, users sometimes encounter an issue where the info window fails to display, particularly when event.completed_item is vim.empty_dict. This article delves into the root causes of this problem, offering detailed insights and practical solutions to ensure a smooth coding workflow.

Understanding the Issue

The mini.completion plugin for Neovim is designed to display an information window with details about the selected completion item. This functionality relies on receiving accurate data about the completed item. However, there are instances where the event.completed_item is an empty dictionary (vim.empty_dict), leading to errors when the plugin attempts to access item details, such as the column (col) information, which results in a failed info window display. This problem is notoriously difficult to reproduce consistently, making troubleshooting a challenge.

Symptoms of the Problem

The primary symptom is that the information window, which should appear when a completion item is selected, does not show up. This can be frustrating, as it deprives the user of valuable context about the selected item. Error messages like the following may appear:

Error executing vim.schedule lua callback: ...m/site/pack/deps/start/mini.nvim/lua/mini/completion.lua:1468: attempt to perform arithmetic on field 'col' (a nil value)
stack traceback:
	...m/site/pack/deps/start/mini.nvim/lua/mini/completion.lua:1468: in function 'info_window_options'
	...m/site/pack/deps/start/mini.nvim/lua/mini/completion.lua:1373: in function ''
	vim/_editor.lua: in function <vim/_editor.lua:0>

These errors indicate that the plugin is trying to perform calculations on a nil value, specifically the col field, which is expected to be a number representing the column position. This usually happens because the event.completed_item is an empty dictionary, lacking the necessary details.

Root Causes

The core issue arises when mini.completion receives an empty dictionary for event.completed_item. This can occur due to several reasons, including:

  1. Timing Issues: Rapid typing or quick selection of completion items might sometimes cause the event to be triggered before all the necessary data is available.
  2. Asynchronous Operations: The completion process often involves asynchronous operations. If the callback is executed before the completion item details are fully populated, it can result in an empty dictionary.
  3. Configuration Conflicts: Incompatibilities with other plugins or custom configurations might interfere with the proper functioning of mini.completion.

Analyzing logs can provide valuable insights into the sequence of events leading to the error. The logs often show a pattern where event.completed_item is set to vim.empty_dict() just before the error occurs. For example:

  }, {
    col = 33,
    item = <table 4>,
    state = "show_info_window"
  }, {
    col = 6,
    item = {
      abbr = "",
      info = "",
      kind = "",
      menu = "",
      user_data = "",
      word = "loichyan"
    },
    state = "auto_info"
  }, {
    item = vim.empty_dict(),
    state = "auto_info"
  }, {
    item = <5>vim.empty_dict(),
    state = "auto_info"
  }, {
    item = <table 5>,
    state = "show_info_window"
  }, {
    item = <table 5>,
    state = "info_window_options:catch(col=nil)"
  }, {
    item = vim.empty_dict(),
    state = "auto_info"
  } }

In this log snippet, the item field being vim.empty_dict() indicates that the completion event did not receive the expected data.

Troubleshooting Steps

To effectively address this issue, follow these troubleshooting steps:

1. Update mini.nvim

Ensure you are using the latest version of mini.nvim. Plugin updates often include bug fixes and performance improvements that can resolve such issues. Update your plugins using your plugin manager (e.g., Packer, Vim-Plug).

2. Review Configuration

Carefully review your mini.completion configuration and other related plugin settings. Look for any custom settings that might be interfering with the plugin's operation. Incompatibilities between plugins can sometimes lead to unexpected behavior.

3. Minimal Configuration Test

Try to reproduce the issue with a minimal Neovim configuration. This involves disabling all plugins except mini.nvim and using a basic init.lua or init.vim file. This step helps isolate whether the problem is specific to your configuration or a general issue with the plugin. Here’s how you can create a minimal init.lua configuration:

-- init.lua

-- Bootstrap lazy.nvim if not already installed
local lazypath = vim.fn.stdpath("data") .. "/lazy/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
  vim.fn.system({
    "git",
    "clone",
    "--filter=blob:none",
    "https://github.com/folke/lazy.nvim.git",
    "--branch=stable", -- latest stable release
    lazypath,
  })
  vim.cmd [[packadd lazy.nvim]]
end

vim.opt.rtp:prepend(lazypath)

-- Load lazy.nvim
require("lazy").setup({
  {
    "echasnovski/mini.nvim",
    version = false, -- disable automatic updates
    lazy = false, -- load on startup
    config = function()
      require("mini.completion").setup()
    end,
  },
})

print("Minimal configuration loaded. Testing mini.completion...")

This configuration loads only mini.nvim using lazy.nvim, which helps ensure a clean testing environment. After setting up the minimal configuration, try to reproduce the issue to see if it persists.

4. Analyze Logs

Enable logging for mini.completion to capture detailed information about the completion process. This can provide clues about when and why the event.completed_item is an empty dictionary. To enable logging, you can modify the plugin's code as suggested in the GitHub issue you referenced. For instance, adding log statements within the auto_info function can help:

local function auto_info(event)
  local item = event.completed_item
  vim.api.nvim_err_writeln(vim.inspect(item)) -- Add this line to log the item

  if vim.tbl_isempty(item) then
    return
  end

  -- ... rest of the function ...
end

By inspecting the logs, you can identify patterns and conditions under which the issue occurs.

5. Check for Asynchronous Issues

If asynchronous operations are suspected, try adding delays or synchronization mechanisms to ensure data is fully available before the info window is displayed. This might involve using vim.schedule to defer the execution of certain tasks or implementing callbacks to handle asynchronous results.

6. Review Completion Sources

Examine your completion sources (e.g., LSP, snippets) to ensure they are providing the necessary data. Misconfigured or malfunctioning completion sources can lead to incomplete or empty completion items.

7. File a Detailed Bug Report

If you've exhausted the troubleshooting steps and can consistently reproduce the issue, consider filing a detailed bug report on the mini.nvim GitHub repository. Include the following information in your report:

  • Neovim version
  • mini.nvim version
  • Minimal configuration to reproduce the issue
  • Detailed steps to reproduce the issue
  • Logs and error messages
  • Any other relevant information (e.g., video recordings)

The more information you provide, the better the chances of the issue being resolved quickly.

Practical Solutions and Workarounds

While a definitive fix might require code changes in mini.completion, here are some practical solutions and workarounds you can implement in the meantime:

1. Debouncing

Implement a debouncing mechanism to prevent the info window from being displayed too quickly after a completion item is selected. This can help avoid race conditions where the data is not yet fully available. Here’s an example of how to implement debouncing using Lua and Neovim’s timers:

local debounce = function(func, delay)
  local timer = nil
  return function(...)
    local args = { ... }
    if timer then
      timer:stop()
    end
    timer = vim.loop.new_timer()
    timer:start(delay, 0, function()
      vim.schedule(function()
        func(unpack(args))
      end)
    end)
  end
end

-- Example usage within mini.completion:
local show_info_window_debounced = debounce(show_info_window, 100) -- 100ms debounce

-- Replace calls to show_info_window with show_info_window_debounced

2. Conditional Checks

Add conditional checks to ensure that event.completed_item contains the necessary data before attempting to display the info window. This can prevent errors when the item is an empty dictionary.

local function show_info_window(event)
  local item = event.completed_item
  if not item or vim.tbl_isempty(item) then
    return -- Exit if item is empty or nil
  end

  -- ... rest of the function ...
end

3. Error Handling

Implement robust error handling to catch and log errors that occur when displaying the info window. This can help identify the root cause of the issue and prevent crashes.

local function show_info_window(event)
  local item = event.completed_item
  if not item or vim.tbl_isempty(item) then
    return
  end

  pcall(function()
    -- Code to display info window
  end, function(err)
    vim.api.nvim_err_writeln("Error showing info window: " .. tostring(err))
  end)
end

4. Manual Retrigger

As a workaround, you can implement a manual retrigger mechanism. If the info window fails to display, you can use a keybinding to manually trigger the display. This provides a way to access the information even if the automatic display fails.

-- Example keybinding
vim.keymap.set("n", "<leader>ci", function()
  -- Code to manually trigger info window display
end, { desc = "Manually trigger completion info window" })

Conclusion

The issue of mini.completion failing to display the info window when event.completed_item is vim.empty_dict can be frustrating, but it is often resolvable with careful troubleshooting and practical solutions. By understanding the root causes, following the troubleshooting steps outlined in this guide, and implementing workarounds, you can mitigate the problem and maintain an efficient coding environment. Remember to keep your plugins updated, review your configuration, and provide detailed bug reports when necessary. With these strategies, you can continue to leverage the power of mini.completion in your Neovim workflow.