org: add property names from #+PROPERTY keywords to completion list

* lisp/org.el (org-buffer-property-keys): Enhance the completion list
with property names from #+PROPERTY keywords, not just property
drawers. Also, for each xxx_ALL property, make sure that the bare xxx
property is added too.

* testing/lisp/test-org.el (test-org/buffer-property-keys): Add test
cases for #+PROPERTY keywords and also for xxx_ALL --> xxx properties.

See https://emacs.stackexchange.com/questions/59448/ for details.

Modified-by: Kyle Meyer <kyle@kyleam.com>
  Cosmetic tweaks to _ALL stripping.

lisp/org.el

@@ -13084,7 +13084,10 @@ COLUMN formats in the current buffer."
 	(props (append
 		(and specials org-special-properties)
 		(and defaults (cons org-effort-property org-default-properties))
-		nil)))
+		;; Get property names from #+PROPERTY keywords as well
+		(mapcar (lambda (s)
+			  (nth 0 (split-string s)))
+			(cdar (org-collect-keywords '("PROPERTY")))))))
     (org-with-wide-buffer
      (goto-char (point-min))
      (while (re-search-forward org-property-start-re nil t)
@@ -13132,7 +13135,15 @@ COLUMN formats in the current buffer."
 		 (let ((p (match-string-no-properties 1 value)))
 		   (unless (member-ignore-case p org-special-properties)
 		     (push p props))))))))))
-    (sort (delete-dups props) (lambda (a b) (string< (upcase a) (upcase b))))))
+    (sort (delete-dups
+	   (append props
+		   ;; for each xxx_ALL property, make sure the bare
+		   ;; xxx property is also included
+		   (delq nil (mapcar (lambda (p)
+				       (and (string-match-p "._ALL\\'" p)
+					    (substring p 0 -4)))
+				     props))))
+	  (lambda (a b) (string< (upcase a) (upcase b))))))
 
 (defun org-property-values (key)
   "List all non-nil values of property KEY in current buffer."

testing/lisp/test-org.el

@@ -5409,6 +5409,27 @@ Paragraph<point>"
    (equal '("A")
 	  (org-test-with-temp-text "* H\n:PROPERTIES:\n:A: 1\n:A+: 2\n:END:"
 	    (org-buffer-property-keys))))
+  ;; Add bare property if xxx_ALL property is there
+  (should
+   (equal '("A" "B" "B_ALL")
+	  (org-test-with-temp-text "* H\n:PROPERTIES:\n:A: 1\n:A+: 2\n:B_ALL: foo bar\n:END:"
+	    (org-buffer-property-keys))))
+  ;; Add bare property if xxx_ALL property is there - check dupes
+  (should
+   (equal '("A" "B" "B_ALL")
+	  (org-test-with-temp-text "* H\n:PROPERTIES:\n:A: 1\n:B: 2\n:B_ALL: foo bar\n:END:"
+	    (org-buffer-property-keys))))
+  ;; Retrieve properties from #+PROPERTY keyword lines
+  (should
+   (equal '("A" "C")
+	  (org-test-with-temp-text "#+PROPERTY: C foo\n* H\n:PROPERTIES:\n:A: 1\n:A+: 2\n:END:"
+	    (org-buffer-property-keys))))
+  ;; Retrieve properties from #+PROPERTY keyword lines - make sure an _ALL property also
+  ;; adds the bare property
+  (should
+   (equal '("A" "C" "C_ALL")
+	  (org-test-with-temp-text "#+PROPERTY: C_ALL foo bar\n* H\n:PROPERTIES:\n:A: 1\n:A+: 2\n:END:"
+	    (org-buffer-property-keys))))
   ;; With non-nil COLUMNS, extract property names from columns.
   (should
    (equal '("A" "B")