emacs: sanitize dedicated widget action/notify functions

These functions are used as action/notify functions.  That dictates
the appropriate function signatures but even though these functions
are not used for anything else they use incompatible signatures,
forcing the callers to use lambda expressions to deal with these
incompatibilities.

Fix that by adjusting the function signatures to the needs of the
only intended callers.

Two of these functions were defined as commands but because the
interactive form did not return the mandatory arguments, we know
that nobody (successfully) used these as commands.

In one case we move the location of a y-or-n-p prompt.

emacs/notmuch-hello.el

@@ -385,18 +385,16 @@ supported for \"Customized queries section\" items."
 		     (format "%s%03d" notmuch-hello-thousands-separator elem))
 		   (cdr result)))))
 
-(defun notmuch-hello-search (&optional search)
+(defun notmuch-hello-search (widget &rest _event)
-  (unless (null search)
+  (let ((search (widget-value widget)))
+    (when search
       (setq search (string-trim search))
       (let ((history-delete-duplicates t))
 	(add-to-history 'notmuch-search-history search)))
-  (notmuch-search search notmuch-search-oldest-first))
+    (notmuch-search search notmuch-search-oldest-first)))
 
-(defun notmuch-hello-add-saved-search (widget)
+(defun notmuch-hello-add-saved-search (widget &rest _event)
-  (interactive)
+  (let ((search (widget-value (widget-get widget :parent)))
-  (let ((search (widget-value
-		 (symbol-value
-		  (widget-get widget :notmuch-saved-search-widget))))
 	(name (completing-read "Name for saved search: "
 			       notmuch-saved-searches)))
     ;; If an existing saved search with this name exists, remove it.
@@ -412,13 +410,11 @@ supported for \"Customized queries section\" items."
     (message "Saved '%s' as '%s'." search name)
     (notmuch-hello-update)))
 
-(defun notmuch-hello-delete-search-from-history (widget)
+(defun notmuch-hello-delete-search-from-history (widget &rest _event)
-  (interactive)
+  (when (y-or-n-p "Are you sure you want to delete this search? ")
-  (let ((search (widget-value
+    (let ((search (widget-value (widget-get widget :parent))))
-		 (symbol-value
+      (setq notmuch-search-history
-		  (widget-get widget :notmuch-saved-search-widget)))))
+	    (delete search notmuch-search-history)))
-    (setq notmuch-search-history (delete search
-					 notmuch-search-history))
     (notmuch-hello-update)))
 
 (defun notmuch-hello-longest-label (searches-alist)
@@ -768,8 +764,7 @@ Complete list of currently available key bindings:
 		 ;; search boxes.
 		 :size (max 8 (- (window-width) notmuch-hello-indent
 				 (length "Search: ")))
-		 :action (lambda (widget &rest ignore)
+		 :action #'notmuch-hello-search)
-			   (notmuch-hello-search (widget-value widget))))
   ;; Add an invisible dot to make `widget-end-of-line' ignore
   ;; trailing spaces in the search widget field.  A dot is used
   ;; instead of a space to make `show-trailing-whitespace'
@@ -816,20 +811,16 @@ Complete list of currently available key bindings:
 						   ;; button. 5 for the
 						   ;; `[del]' button.
 						   1 5))
-				     :action (lambda (widget &rest ignore)
+				     :action #'notmuch-hello-search
-					       (notmuch-hello-search (widget-value widget)))
 				     search))
 		 (widget-insert " ")
 		 (widget-create 'push-button
-				:notify (lambda (widget &rest ignore)
+				:notify #'notmuch-hello-add-saved-search
-					  (notmuch-hello-add-saved-search widget))
 				:notmuch-saved-search-widget widget-symbol
 				"save")
 		 (widget-insert " ")
 		 (widget-create 'push-button
-				:notify (lambda (widget &rest ignore)
+				:notify #'notmuch-hello-delete-search-from-history
-					  (when (y-or-n-p "Are you sure you want to delete this search? ")
-					    (notmuch-hello-delete-search-from-history widget)))
 				:notmuch-saved-search-widget widget-symbol
 				"del"))
 	       (widget-insert "\n"))