Handle quotation marks and apostrophes in ‘sgml-quote’

To be able to use text in an HTML argument, quotation marks need
to be replaced with an appropriate character reference.  Make
‘sgml-quote’ do that.

While at it, fix entiteis not being unquoted if they lack closing
semicolon (e.g. ‘&amp’) occuring at the very end of a region.
Even though unlikely, make ‘sgml-quote’ handle this scenario.

* lisp/textmodes/sgml-mode.el (sgml-quote): Handle quotation marks and
apostrophes.  Match entities lacking semicolon at the end of regions.
* test/lisp/textmodes/sgml-mode-tests.el (sgml-quote-works): New test
case for ‘sgml-quote’ function.

1 files changed, 30 insertions, 0 deletions

diff --git a/test/lisp/textmodes/sgml-mode-tests.el b/test/lisp/textmodes/sgml-mode-tests.el
index 7ca6e676c64..6c0070ccb1e 100644
--- a/test/lisp/textmodes/sgml-mode-tests.el
+++ b/test/lisp/textmodes/sgml-mode-tests.el
@@ -131,5 +131,35 @@ The point is set to the beginning of the buffer."
    (sgml-delete-tag 1)
    (should (string= "Winter is comin'" (buffer-string)))))
 
+(ert-deftest sgml-quote-works ()
+  (let ((text "Foo<Bar> \"Baz\" 'Qux'\n"))
+    (with-temp-buffer
+      ;; Back and forth transformation.
+      (insert text)
+      (sgml-quote (point-min) (point-max))
+      (should (string= "Foo&lt;Bar&gt; &#34;Baz&#34; &#39;Qux&#39;\n"
+                       (buffer-string)))
+      (sgml-quote (point-min) (point-max) t)
+      (should (string= text (buffer-string)))
+
+      ;; The same text escaped differently.
+      (erase-buffer)
+      (insert "Foo&lt;Bar&gt; &#34;Baz&quot; &#x27;Qux&#X27;\n")
+      (sgml-quote (point-min) (point-max) t)
+      (should (string= text (buffer-string)))
+
+      ;; Lack of semicolon.
+      (erase-buffer)
+      (insert "&amp&amp")
+      (sgml-quote (point-min) (point-max) t)
+      (should (string= "&&" (buffer-string)))
+
+      ;; Double quoting
+      (sgml-quote (point-min) (point-max))
+      (sgml-quote (point-min) (point-max))
+      (sgml-quote (point-min) (point-max) t)
+      (sgml-quote (point-min) (point-max) t)
+      (should (string= "&&" (buffer-string))))))
+
 (provide 'sgml-mode-tests)
 ;;; sgml-mode-tests.el ends here