bug#36092: 27.0.50; incorrect highlighting in nXML mode with ' and raw > characters

[Noam Postavsky]

Vincent Lefevre <vincent@vinc17.net> writes:

> On the following file, lines 26 and below are not highlighted
> (i.e. they get the normal color). This is reproducible with
> and without the -Q option.

It's hitting an assertion failure during syntax-propertizing.  The
problem seems to be that the parse-partial-sexp call in
sgml--syntax-propertize-ppss isn't using the right syntax table.  I
wonder why it doesn't happen for sgml-mode though (as far I can tell).
Stefan, any thoughts about that?

Patch below fixes it, but it might just be papering over another
problem.

>From ed59843b7fa456e0614c2c63e1479458642671ea Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Tue, 4 Jun 2019 21:08:26 -0400
Subject: [PATCH] Fix nxml syntax propertizing assertion failure (Bug#36092)

* lisp/textmodes/sgml-mode.el (sgml-syntax-propertize): Use the
syntax-ppss-table syntax-table.
* test/lisp/nxml/nxml-mode-tests.el (nxml-mode->-after-quote): New
test.
---
 lisp/textmodes/sgml-mode.el       | 17 +++++++++--------
 test/lisp/nxml/nxml-mode-tests.el | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/lisp/textmodes/sgml-mode.el b/lisp/textmodes/sgml-mode.el
index 0c5d5e56a6..09211e1661 100644
--- a/lisp/textmodes/sgml-mode.el
+++ b/lisp/textmodes/sgml-mode.el
@@ -399,14 +399,15 @@ (eval-and-compile
 
 (defun sgml-syntax-propertize (start end)
   "Syntactic keywords for `sgml-mode'."
-  (setq sgml--syntax-propertize-ppss (cons start (syntax-ppss start)))
-  (cl-assert (>= (cadr sgml--syntax-propertize-ppss) 0))
-  (sgml-syntax-propertize-inside end)
-  (funcall
-   (syntax-propertize-rules sgml-syntax-propertize-rules)
-   start end)
-  ;; Catch any '>' after the last quote.
-  (sgml--syntax-propertize-ppss end))
+  (with-syntax-table syntax-ppss-table
+    (setq sgml--syntax-propertize-ppss (cons start (syntax-ppss start)))
+    (cl-assert (>= (cadr sgml--syntax-propertize-ppss) 0))
+    (sgml-syntax-propertize-inside end)
+    (funcall
+     (syntax-propertize-rules sgml-syntax-propertize-rules)
+     start end)
+    ;; Catch any '>' after the last quote.
+    (sgml--syntax-propertize-ppss end)))
 
 (defun sgml-syntax-propertize-inside (end)
   (let ((ppss (syntax-ppss)))
diff --git a/test/lisp/nxml/nxml-mode-tests.el 
b/test/lisp/nxml/nxml-mode-tests.el
index 70816bb9de..53416b4280 100644
--- a/test/lisp/nxml/nxml-mode-tests.el
+++ b/test/lisp/nxml/nxml-mode-tests.el
@@ -99,5 +99,20 @@ (ert-deftest nxml-mode-prolog-comment ()
     (should (nth 4 (syntax-ppss)))
     (search-forward "comment3")))
 
+(ert-deftest nxml-mode->-after-quote ()
+  "Reduction from Bug#36092."
+  (with-temp-buffer
+    (insert "<root>\n"
+            (make-string 1794 ?a) "\n"
+            "'>"
+            (make-string 196 ?a) "\n"
+            "</root>")
+    (nxml-mode)
+    (syntax-propertize 2001)
+    (syntax-propertize (point-max))     ; Triggered an assert failure.
+    ;; Check that last tag is parsed as a tag.
+    (should (= 1 (- (car (syntax-ppss (1- (point-max))))
+                    (car (syntax-ppss (point-max))))))))
+
 (provide 'nxml-mode-tests)
 ;;; nxml-mode-tests.el ends here
-- 
2.11.0