fix: spurious exits from faulty :wq detection (#221)

The previous mechanism used histget() to get the last command or
expression to detect if the user issued a `:wq` or similar. This had the
issue where if a user issued a `:wq`, started vim again, then entered
oil and saved via some mechanism that is _not_ a command (e.g. a
keymap), we would incorrectly detect that `:wq` and exit after saving.
The new mechanism tracks all keypresses and may end up with false
negatives (e.g. ":wqaff<backspace><backspace>ll"), but those are less
frustrating than false positives.

lua/oil/init.lua

@@ -926,9 +926,11 @@ local function close_preview_window_if_not_in_oil()
   pcall(vim.api.nvim_win_close, preview_win_id, true)
 end
 
+local _on_key_ns = 0
 ---Initialize oil
 ---@param opts nil|table
 M.setup = function(opts)
+  local Ringbuf = require("oil.ringbuf")
   local config = require("oil.config")
 
   config.setup(opts)
@@ -999,6 +1001,12 @@ M.setup = function(opts)
     pattern = filetype_patterns,
   })
 
+  local keybuf = Ringbuf.new(7)
+  if _on_key_ns == 0 then
+    _on_key_ns = vim.on_key(function(char)
+      keybuf:push(char)
+    end, _on_key_ns)
+  end
   vim.api.nvim_create_autocmd("ColorScheme", {
     desc = "Set default oil highlights",
     group = aug,
@@ -1018,12 +1026,15 @@ M.setup = function(opts)
     pattern = scheme_pattern,
     nested = true,
     callback = function(params)
+      local last_keys = keybuf:as_str()
       local winid = vim.api.nvim_get_current_win()
-      local last_cmd = vim.fn.histget("cmd", -1)
-      local last_expr = vim.fn.histget("expr", -1)
       -- If the user issued a :wq or similar, we should quit after saving
-      local quit_after_save = last_cmd == "wq" or last_cmd == "x" or last_expr == "ZZ"
+      local quit_after_save = vim.endswith(last_keys, ":wq\r")
-      local quit_all = last_cmd:match("^wqal*$")
+        or vim.endswith(last_keys, ":x\r")
+        or vim.endswith(last_keys, "ZZ")
+      local quit_all = vim.endswith(last_keys, ":wqa\r")
+        or vim.endswith(last_keys, ":wqal\r")
+        or vim.endswith(last_keys, ":wqall\r")
       local bufname = vim.api.nvim_buf_get_name(params.buf)
       if vim.endswith(bufname, "/") then
         vim.cmd.doautocmd({ args = { "BufWritePre", params.file }, mods = { silent = true } })

lua/oil/ringbuf.lua

@@ -0,0 +1,37 @@
+---@class oil.Ringbuf
+---@field private size integer
+---@field private tail integer
+---@field private buf string[]
+local Ringbuf = {}
+function Ringbuf.new(size)
+  local self = setmetatable({
+    size = size,
+    buf = {},
+    tail = 0,
+  }, { __index = Ringbuf })
+  return self
+end
+
+---@param val string
+function Ringbuf:push(val)
+  self.tail = self.tail + 1
+  if self.tail > self.size then
+    self.tail = 1
+  end
+  self.buf[self.tail] = val
+end
+
+---@return string
+function Ringbuf:as_str()
+  local postfix = ""
+  for i = 1, self.tail, 1 do
+    postfix = postfix .. self.buf[i]
+  end
+  local prefix = ""
+  for i = self.tail + 1, #self.buf, 1 do
+    prefix = prefix .. self.buf[i]
+  end
+  return prefix .. postfix
+end
+
+return Ringbuf