Prevent spurious tabs by RET in todo-edit-mode (bug#43068)

* lisp/calendar/todo-mode.el (todo-key-bindings-t)
(todo-edit-mode-map): Remove remapping of `newline' to
`newline-and-indent'.
(todo-modes-set-1): Remove local setting of `indent-line-function'.
(todo-edit-mode): Locally set `indent-line-function' to `todo-indent'.

* test/lisp/calendar/todo-mode-tests.el (todo-test-move-item05):
Prevent interactive test failure.  (Until the addition of testcat4
to todo-test-1.todo, the test passed by chance, since testcat3 is
empty and has no archived items.)
(todo-test-edit-item-date-month): Refer to bug number.
(todo-test-multiline-item-indentation-1)
(todo-test-multiline-item-indentation-2)
(todo-test-multiline-item-indentation-3): New tests.

* test/lisp/calendar/todo-mode-resources/todo-test-1.todo: Remove
spurious tabs from testcat1.

lisp/calendar/todo-mode.el

@@ -6440,8 +6440,7 @@ Filtered Items mode following todo (not done) items."
     ("i"	     todo-insert-item)
     ("k"	     todo-delete-item)
     ("m"	     todo-move-item)
-    ("u"	     todo-item-undone)
-    ([remap newline] newline-and-indent))
+    ("u"	     todo-item-undone))
   "List of key bindings for Todo mode only.")
 
 (defvar todo-key-bindings-t+a+f
@@ -6507,7 +6506,6 @@ Filtered Items mode following todo (not done) items."
 (defvar todo-edit-mode-map
   (let ((map (make-sparse-keymap)))
     (define-key map "\C-x\C-q" 'todo-edit-quit)
-    (define-key map [remap newline] 'newline-and-indent)
     map)
   "Todo Edit mode keymap.")
 
@@ -6666,7 +6664,6 @@ Added to `window-configuration-change-hook' in Todo mode."
   (setq-local font-lock-defaults '(todo-font-lock-keywords t))
   (setq-local revert-buffer-function #'todo-revert-buffer)
   (setq-local tab-width todo-indent-to-here)
-  (setq-local indent-line-function #'todo-indent)
   (when todo-wrap-lines
     (visual-line-mode)
     (setq wrap-prefix (make-string todo-indent-to-here 32))))
@@ -6741,6 +6738,7 @@ Added to `window-configuration-change-hook' in Todo mode."
 
 \\{todo-edit-mode-map}"
   (todo-modes-set-1)
+  (setq-local indent-line-function #'todo-indent)
   (if (> (buffer-size) (- (point-max) (point-min)))
       ;; Editing one item in an indirect buffer, so buffer-file-name is nil.
       (setq-local todo-current-todo-file todo-global-current-todo-file)

test/lisp/calendar/todo-mode-resources/todo-test-1.todo

@@ -1,8 +1,8 @@
 (("testcat1" . [2 0 2 1]) ("testcat2" . [3 0 1 1]) ("testcat3" . [0 0 0 0]) ("testcat4" . [1 0 0 0]))
 --==-- testcat1
 [May 29, 2017] testcat1 item3
-		has more than one line
-		to test item highlighting
+	has more than one line
+	to test item highlighting
 [Jul 3, 2017] testcat1 item4
 
 ==--== DONE 

test/lisp/calendar/todo-mode-tests.el

@@ -414,8 +414,15 @@ the top done item should be the first done item."
      (should (todo-done-item-p))
      (forward-line -1)
      (should (looking-at todo-category-done))
-     ;; Make sure marked items are no longer in first category.
-     (todo-backward-category)
+     ;; Make sure marked items are no longer in first category.  Since
+     ;; cat1 now contains no todo or done items but does have archived
+     ;; items, todo-backward-category would skip it by default, so
+     ;; prevent this. (FIXME: Without this let-binding,
+     ;; todo-backward-category selects the nonempty cat4 and this test
+     ;; fails as expected when run interactively but not in a batch
+     ;; run -- why?)
+     (let (todo-skip-archived-categories)
+       (todo-backward-category))
      (should (eq (point-min) (point-max))) ; All todo items were moved.
      ;; This passes when run interactively but fails in a batch run:
      ;; the message is displayed but (current-message) evaluates to
@@ -848,7 +855,7 @@ should display the previously current (or default) todo file."
      (should (equal todo-current-todo-file todo-test-file-1))
      (delete-file (concat file "~")))))
 
-(ert-deftest todo-test-edit-item-date-month ()
+(ert-deftest todo-test-edit-item-date-month () ; bug#42976 #3 and #4
   "Test incrementing and decrementing the month of an item's date.
 If the change in month crosses a year boundary, the year of the
 item's date should be adjusted accordingly."
@@ -892,8 +899,50 @@ item's date should be adjusted accordingly."
      (todo-edit-item--header 'month 25)
      (should (equal (funcall get-date) "Feb 1, 2022"))
      (todo-edit-item--header 'month -25)
-     (should (equal (funcall get-date) "Jan 1, 2020"))
-     )))
+     (should (equal (funcall get-date) "Jan 1, 2020")))))
+
+(ert-deftest todo-test-multiline-item-indentation-1 ()
+  "Test inserting a multine item containing a hard line break.
+After insertion the second line of the item should begin with a
+tab character."
+  (with-todo-test
+   (let* ((item0 "Test inserting a multine item")
+          (item1 "containing a hard line break.")
+          (item (concat item0 "\n" item1)))
+     (todo-test--show 1)
+     (todo-test--insert-item item 1)
+     (re-search-forward (concat todo-date-string-start todo-date-pattern
+				(regexp-quote todo-nondiary-end) " ")
+			(line-end-position) t)
+     (should (looking-at (regexp-quote (concat item0 "\n\t" item1)))))))
+
+(ert-deftest todo-test-multiline-item-indentation-2 () ; bug#43068
+  "Test editing an item by adding text on a new line.
+After quitting todo-edit-mode the second line of the item should
+begin with a tab character."
+  (with-todo-test
+   (todo-test--show 2)
+   (let* ((item0 (todo-item-string))
+          (item1 "Second line."))
+     (todo-edit-item--text 'multiline)
+     (insert (concat "\n" item1))
+     (todo-edit-quit)
+     (goto-char (line-beginning-position))
+     (should (looking-at (regexp-quote (concat item0 "\n\t" item1)))))))
+
+(ert-deftest todo-test-multiline-item-indentation-3 ()
+  "Test adding an unindented new line to an item using todo-edit-file.
+Attempting to quit todo-edit-mode should signal a user-error,
+since all non-initial item lines must begin with whitespace."
+  (with-todo-test
+   (todo-test--show 2)
+   (let* ((item0 (todo-item-string))
+          (item1 "Second line."))
+     (todo-edit-file)
+     (should (looking-at (regexp-quote item0)))
+     (goto-char (line-end-position))
+     (insert (concat "\n" item1))
+     (should-error (todo-edit-quit) :type 'user-error))))
 
 (provide 'todo-mode-tests)
 ;;; todo-mode-tests.el ends here