Keep nxml prolog updated via syntax-propertize

Instead of using after-change-functions.  Also, stop consulting
nxml-prolog-regions during syntax-propertize.  It turns out the
problems fixed by using prolog information are actually due to using
the wrong syntax table during propertizing.  This was fixed in
2019-06-04 "* lisp/emacs-lisp/syntax.el: Use syntax-ppss-table for
syntax-propertize." so consulting the prolog data is no longer needed.
* lisp/nxml/nxml-rap.el (nxml-maybe-rescan-prolog): Remove.
* lisp/nxml/nxml-mode.el (nxml-mode): Stop using it.
(nxml-syntax-propertize): Don't use nxml-prolog-regions, just call
nxml-scan-prolog if needed before delegating to
sgml-syntax-propertize.
* test/lisp/nxml/nxml-mode-tests.el (nxml-mode-edit-prolog): New test.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/lisp/nxml/nxml-mode-tests.el b/test/lisp/nxml/nxml-mode-tests.el
index 53416b4280c..e9b4fb7c7e1 100644
--- a/test/lisp/nxml/nxml-mode-tests.el
+++ b/test/lisp/nxml/nxml-mode-tests.el
@@ -114,5 +114,23 @@
     (should (= 1 (- (car (syntax-ppss (1- (point-max))))
                     (car (syntax-ppss (point-max))))))))
 
+(ert-deftest nxml-mode-edit-prolog ()
+  "Test for Bug#23668."
+  (with-temp-buffer
+    (insert "
+ <t>
+ <sub/>
+</t>")
+    (nxml-mode)
+    ;; The leading "\n " before "<t>" is the prolog, indenting will
+    ;; delete the space hence changing the prolog size.  If that is
+    ;; not taken into account, then the <sub/> tag won't be indented
+    ;; correctly.
+    (indent-region (point-min) (point-max))
+    (should (equal (buffer-string) "
+<t>
+  <sub/>
+</t>"))))
+
 (provide 'nxml-mode-tests)
 ;;; nxml-mode-tests.el ends here