org-export: Run a hook just before expanding include keywords and macros

* contrib/lisp/org-export.el (org-export-before-processing-hook): New
  variable.
(org-export-as): Run a hook just before expanding include keywords and
macros, and evaluating Babel blocks.
* testing/lisp/test-org-export.el: Add test.

contrib/lisp/org-export.el

@@ -2083,19 +2083,32 @@ Any element in `:ignore-list' will be skipped when using
 ;; Filters properties are installed in communication channel with
 ;; `org-export-install-filters' function.
 ;;
-;; Eventually, a hook (`org-export-before-parsing-hook') is run just
+;; Eventually, two hooks (`org-export-before-processing-hook' and
-;; before parsing to allow for heavy structure modifications.
+;; `org-export-before-parsing-hook') are run at the beginning of the
+;; export process and just before parsing to allow for heavy structure
+;; modifications.
 
 
-;;;; Before Parsing Hook
+;;;; Hooks
+
+(defvar org-export-before-processing-hook nil
+  "Hook run at the beginning of the export process.
+
+This is run before include keywords and macros are expanded and
+Babel code blocks executed, on a copy of the original buffer
+being exported.  Visibility and narrowing are preserved.  Point
+is at the beginning of the buffer.
+
+Every function in this hook will be called with one argument: the
+back-end currently used, as a symbol.")
 
 (defvar org-export-before-parsing-hook nil
   "Hook run before parsing an export buffer.
 
-This is run after include keywords have been expanded and Babel
+This is run after include keywords and macros have been expanded
-code executed, on a copy of original buffer's area being
+and Babel code blocks executed, on a copy of the original buffer
-exported.  Visibility is the same as in the original one.  Point
+being exported.  Visibility and narrowing are preserved.  Point
-is left at the beginning of the new one.
+is at the beginning of the buffer.
 
 Every function in this hook will be called with one argument: the
 back-end currently used, as a symbol.")
@@ -2580,6 +2593,8 @@ Return code as a string."
       ;; attributes, unavailable in its copy.
       (let ((info (org-export--get-buffer-attributes)) tree)
 	(org-export-with-current-buffer-copy
+	 ;; Run first hook with current back-end as argument.
+	 (run-hook-with-args 'org-export-before-processing-hook backend)
 	 ;; Update communication channel and get parse tree.  Buffer
 	 ;; isn't parsed directly.  Instead, a temporary copy is
 	 ;; created, where include keywords, macros are expanded and
@@ -2600,8 +2615,7 @@ Return code as a string."
 	 ;; Update radio targets since keyword inclusion might have
 	 ;; added some more.
 	 (org-update-radio-target-regexp)
-	 ;; Run hook `org-export-before-parsing-hook'. with current
+	 ;; Run last hook with current back-end as argument.
-	 ;; back-end as argument.
 	 (goto-char (point-min))
 	 (run-hook-with-args 'org-export-before-parsing-hook backend)
 	 ;; Update communication channel with environment.  Also

testing/lisp/test-org-export.el

@@ -492,8 +492,27 @@ body\n")))
 	(org-test-with-temp-text "* Head1\n* Head2 (note)\n"
 	  (should (equal (org-export-as 'test) "* Head1\n")))))))
 
+(ert-deftest test-org-export/before-processing-hook ()
+  "Test `org-export-before-processing-hook'."
+  (should
+   (equal
+    "#+MACRO: mac val\nTest\n"
+    (org-test-with-backend test
+      (org-test-with-temp-text "#+MACRO: mac val\n{{{mac}}} Test"
+	(let ((org-export-before-processing-hook
+	       '((lambda (backend)
+		   (while (re-search-forward "{{{" nil t)
+		     (let ((object (org-element-context)))
+		       (when (eq (org-element-type object) 'macro)
+			 (delete-region
+			  (org-element-property :begin object)
+			  (org-element-property :end object)))))))))
+	  (org-export-as 'test)))))))
+
 (ert-deftest test-org-export/before-parsing-hook ()
   "Test `org-export-before-parsing-hook'."
+  (should
+   (equal "Body 1\nBody 2\n"
 	  (org-test-with-backend test
 	    (org-test-with-temp-text "* Headline 1\nBody 1\n* Headline 2\nBody 2"
 	      (let ((org-export-before-parsing-hook
@@ -501,7 +520,7 @@ body\n")))
 			 (org-map-entries
 			  (lambda ()
 			    (delete-region (point) (progn (forward-line) (point)))))))))
-	(should (equal (org-export-as 'test) "Body 1\nBody 2\n"))))))
+		(org-export-as 'test)))))))