From 85b8ccab3d5e43a4a3d4e622529248973b606a04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Harald=20J=C3=B6rg?= <haj@posteo.de>
Date: Thu, 29 Oct 2020 21:03:12 +0100
Subject: [PATCH] ; Suppress a misleading message when closing a paren in a
 regex

* lisp/progmodes/cperl-mode.el (cperl-forward-re): Suppress an
error message about "End of string/RE not found" when we are
at the end of a narrowed buffer where the end of a RE is
temporarily unavailable (Bug#37127).

* test/lisp/progmodes/cperl-mode-tests.el (cperl-bug37127):
Add a test to verify that the message is suppressed when
inappropriate, but appears when the RE *is* incomplete.
---
 lisp/progmodes/cperl-mode.el            |  7 ++++++
 test/lisp/progmodes/cperl-mode-tests.el | 29 +++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/lisp/progmodes/cperl-mode.el b/lisp/progmodes/cperl-mode.el
index ebbea6bed9..94f42cb2bc 100644
--- a/lisp/progmodes/cperl-mode.el
+++ b/lisp/progmodes/cperl-mode.el
@@ -3225,6 +3225,13 @@ cperl-forward-re
 		 (and cperl-brace-recursing
 		      (or (eq ostart  ?\{)
 			  (eq starter ?\{)))
+		 ;; If we are at the end of a narrowed buffer, then a
+		 ;; scan error should not be reported to the user.
+		 ;; This situation actually happens when a closing
+		 ;; paren is entered in a regular expression.
+		 ;; Reported in Bug#37127.
+		 (and (eobp) (buffer-narrowed-p)
+		      (equal (car bb) 'scan-error))
 		 (message
 		  "End of `%s%s%c ... %c' string/RE not found: %s"
 		  argument
diff --git a/test/lisp/progmodes/cperl-mode-tests.el b/test/lisp/progmodes/cperl-mode-tests.el
index e67678cf6b..4b949bc9a7 100644
--- a/test/lisp/progmodes/cperl-mode-tests.el
+++ b/test/lisp/progmodes/cperl-mode-tests.el
@@ -218,4 +218,33 @@ cperl-mode-fontify-punct-vars
         (should (equal (nth 3 (syntax-ppss)) nil))
         (should (equal (nth 4 (syntax-ppss)) t))))))
 
+(ert-deftest cperl-bug37127 ()
+  "Verify that closing a paren in a regex goes without a message.
+Also check that the message is issued if the regex terminator is
+missing."
+  (let (collected-messages)
+    ;; Part one: Regex is ok, no messages
+    (ert-with-message-capture collected-messages
+      (with-temp-buffer
+        (insert "$_ =~ /(./;")
+        (cperl-mode)
+        (goto-char (point-min))
+        (search-forward ".")
+        (let ((last-command-event ?\)))
+          (cperl-electric-rparen 1)
+          (cperl-find-pods-heres (point-min) (point-max) t)))
+      (should (string-equal collected-messages "")))
+    ;; part two: Regex terminator missing -> message
+    (ert-with-message-capture collected-messages
+      (with-temp-buffer
+        (insert "$_ =~ /(..;")
+        (goto-char (point-min))
+        (cperl-mode)
+        (search-forward ".")
+        (let ((last-command-event ?\)))
+          (cperl-electric-rparen 1)
+          (cperl-find-pods-heres (point-min) (point-max) t)))
+      (should (string-match "^End of .* string/RE"
+                            collected-messages)))))
+
 ;;; cperl-mode-tests.el ends here
-- 
2.20.1