feat: warn on dirty buffer before store-dependent actions (#83)

* fix(buffer): use `default_category` config for empty placeholder

Problem: The empty-buffer fallback hardcoded the category name `TODO`,
ignoring the user's `default_category` config value (default: `Todo`).

Solution: Read `config.get().default_category` at render time and use
that value for both the header line and `LineMeta` category field.

* fix(diff): match optional checkbox char in `parse_buffer` patterns

Problem: `parse_buffer` used `%[.%]` which requires exactly one
character between brackets, failing to parse empty `[]` checkboxes.

Solution: Change to `%[.?%]` so the character is optional, matching
`[]`, `[ ]`, `[x]`, and `[!]` uniformly.

* fix(init): add `nowait` to buffer keymap opts

Problem: Buffer-local mappings like `!` could be swallowed by Neovim's
operator-pending machinery or by global maps sharing a prefix, since
the keymap opts did not include `nowait`.

Solution: Add `nowait = true` to the shared `opts` table used for all
buffer-local mappings in `_setup_buf_mappings`.

* feat(init): allow `:Pending done` with no args to use cursor line

Problem: `:Pending done` required an explicit task ID, making it
awkward to mark the current task done while inside the pending buffer.

Solution: When called with no ID, `M.done()` reads the cursor row from
`buffer.meta()` to resolve the task ID, erroring if the cursor is not
on a saved task line.

* fix(views): populate `priority` field in `LineMeta`

Problem: Both `category_view` and `priority_view` omitted `priority`
from the `LineMeta` they produced. `apply_extmarks` checks `m.priority`
to decide whether to render the priority icon, so it was always nil,
causing the `[ ]` pending-icon overlay to replace the `[!]` buffer text.

Solution: Add `priority = task.priority` to both LineMeta constructors.

* fix(buffer): keep `_meta` in sync when `open_line` inserts a new line

Problem: `open_line` inserted a buffer line without updating `_meta`,
leaving the entry at that row pointing to the task that was shifted
down. Pressing `<CR>` (toggle_complete) would read the stale meta,
find a real task ID, toggle it, and re-render — destroying the unsaved
new line.

Solution: Insert a `{ type = 'blank' }` sentinel into `_meta` at the
new line's position so buffer-local actions see no task there.

* fix(buffer): use task sentinel in `open_line` for better unsaved-task errors

* feat(init): warn on dirty buffer before store-dependent actions

Problem: `toggle_complete`, `toggle_priority`, `prompt_date`, and
`done` (no-args) all read from `buffer.meta()` which is stale whenever
the buffer has unsaved edits, leading to silent no-ops or acting on the
wrong task.

Solution: Add a `require_saved()` guard that emits a `log.warn` and
returns false when the buffer is modified. Each store-dependent action
calls it before touching meta or the store.

* fix(init): guard `view`, `undo`, and `filter` against dirty buffer

Problem: `toggle_view`, `undo_write`, and `filter` all call
`buffer.render()` which rewrites the buffer from the store, silently
discarding any unsaved edits. The previous `require_saved()` change
missed these three entry points.

Solution: Add `require_saved()` to the `view` and `filter` keymap
lambdas and to `M.undo_write()`. Also guard `M.filter()` directly so
`:Pending filter` from the command line is covered too.

* fix(init): improve dirty-buffer warning message

* fix(init): tighten dirty-buffer warning message

lua/pending/buffer.lua

@@ -133,6 +133,7 @@ function M.open_line(above)
   local insert_row = above and (row - 1) or row
   vim.bo[bufnr].modifiable = true
   vim.api.nvim_buf_set_lines(bufnr, insert_row, insert_row, false, { '- [ ] ' })
+  table.insert(_meta, insert_row + 1, { type = 'task' })
   vim.api.nvim_win_set_cursor(0, { insert_row + 1, 6 })
   vim.cmd('startinsert!')
 end

lua/pending/init.lua

@@ -83,6 +83,16 @@ local function _save_and_notify()
   M._recompute_counts()
 end
 
+---@return boolean
+local function require_saved()
+  local bufnr = buffer.bufnr()
+  if bufnr and vim.bo[bufnr].modified then
+    log.warn('save changes first (:w)')
+    return false
+  end
+  return true
+end
+
 ---@return pending.Counts
 function M.counts()
   if not _counts then
@@ -175,6 +185,9 @@ end
 ---@param pred_str string
 ---@return nil
 function M.filter(pred_str)
+  if not require_saved() then
+    return
+  end
   if pred_str == 'clear' or pred_str == '' then
     buffer.set_filter({}, {})
     local bufnr = buffer.bufnr()
@@ -232,7 +245,7 @@ end
 function M._setup_buf_mappings(bufnr)
   local cfg = require('pending.config').get()
   local km = cfg.keymaps
-  local opts = { buffer = bufnr, silent = true }
+  local opts = { buffer = bufnr, silent = true, nowait = true }
 
   ---@type table<string, fun()>
   local actions = {
@@ -243,6 +256,9 @@ function M._setup_buf_mappings(bufnr)
       M.toggle_complete()
     end,
     view = function()
+      if not require_saved() then
+        return
+      end
       buffer.toggle_view()
     end,
     priority = function()
@@ -255,6 +271,9 @@ function M._setup_buf_mappings(bufnr)
       M.undo_write()
     end,
     filter = function()
+      if not require_saved() then
+        return
+      end
       vim.ui.input({ prompt = 'Filter: ' }, function(input)
         if input then
           M.filter(input)
@@ -370,6 +389,9 @@ end
 
 ---@return nil
 function M.undo_write()
+  if not require_saved() then
+    return
+  end
   local s = get_store()
   local stack = s:undo_stack()
   if #stack == 0 then
@@ -388,6 +410,9 @@ function M.toggle_complete()
   if not bufnr then
     return
   end
+  if not require_saved() then
+    return
+  end
   local row = vim.api.nvim_win_get_cursor(0)[1]
   local meta = buffer.meta()
   if not meta[row] or meta[row].type ~= 'task' then
@@ -430,13 +455,30 @@ function M.toggle_complete()
   end
 end
 
----@param id_str string
+---@param id_str? string
 ---@return nil
 function M.done(id_str)
-  local id = tonumber(id_str)
-  if not id then
-    log.error('Invalid task ID: ' .. tostring(id_str))
-    return
+  local id
+  if not id_str or id_str == '' then
+    if not require_saved() then
+      return
+    end
+    local row = vim.api.nvim_win_get_cursor(0)[1]
+    local meta = buffer.meta()
+    if not meta[row] or meta[row].type ~= 'task' then
+      log.error('Cursor is not on a task line.')
+      return
+    end
+    id = meta[row].id
+    if not id then
+      return
+    end
+  else
+    id = tonumber(id_str)
+    if not id then
+      log.error('Invalid task ID: ' .. tostring(id_str))
+      return
+    end
   end
   local s = get_store()
   s:load()
@@ -478,6 +520,9 @@ function M.toggle_priority()
   if not bufnr then
     return
   end
+  if not require_saved() then
+    return
+  end
   local row = vim.api.nvim_win_get_cursor(0)[1]
   local meta = buffer.meta()
   if not meta[row] or meta[row].type ~= 'task' then
@@ -510,6 +555,9 @@ function M.prompt_date()
   if not bufnr then
     return
   end
+  if not require_saved() then
+    return
+  end
   local row = vim.api.nvim_win_get_cursor(0)[1]
   local meta = buffer.meta()
   if not meta[row] or meta[row].type ~= 'task' then

lua/pending/views.lua

@@ -156,6 +156,7 @@ function M.category_view(tasks)
         raw_due = task.due,
         status = task.status,
         category = cat,
+        priority = task.priority,
         overdue = task.status == 'pending' and task.due ~= nil and parse.is_overdue(task.due)
           or nil,
         recur = task.recur,
@@ -207,6 +208,7 @@ function M.priority_view(tasks)
       raw_due = task.due,
       status = task.status,
       category = task.category,
+      priority = task.priority,
       overdue = task.status == 'pending' and task.due ~= nil and parse.is_overdue(task.due) or nil,
       show_category = true,
       recur = task.recur,