bug#55690: 29.0.50; hs-hide-all hangs if backslash escaped newline is used in Python class/function definition

[kobarity <kobarity@gmail.com>]

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The problem is that python-nav-end-of-defun used in
python-hideshow-forward-sexp-function can not handle backslash escaped
newline in class/function definitions. Attached is a patch to fix the
problem.

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commit 8c2eacc6038da9a9a5b3b6dc3c76823fe1f0e7f1
Author: kobarity <kobarity@gmail.com>
Date:   Sat May 28 23:59:06 2022 +0900

    Fix Python Hideshow problem with backslash escaped newlines
    
    * lisp/progmodes/python.el (python-rx)
    (python-nav-beginning-of-defun-regexp): Allow
    python-nav-*-defun to handle backslash escaped newlines
    (bug#55690).

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 9adbb82abf..c2483436fe 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -359,7 +359,8 @@ python-mode-map
 (defmacro python-rx (&rest regexps)
   "Python mode specialized rx macro.
 This variant of `rx' supports common Python named REGEXPS."
-  `(rx-let ((block-start       (seq symbol-start
+  `(rx-let ((sp-bsnl (or space (and ?\\ ?\n)))
+            (block-start       (seq symbol-start
                                     (or "def" "class" "if" "elif" "else" "try"
                                         "except" "finally" "for" "while" "with"
                                         ;; Python 3.10+ PEP634
@@ -1439,7 +1440,7 @@ python-forward-sexp-function
                  function))
 
 (defvar python-nav-beginning-of-defun-regexp
-  (python-rx line-start (* space) defun (+ space) (group symbol-name))
+  (python-rx line-start (* space) defun (+ sp-bsnl) (group symbol-name))
   "Regexp matching class or function definition.
 The name of the defun should be grouped so it can be retrieved
 via `match-string'.")
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index 479d68a062..8db0a07170 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -1861,6 +1861,22 @@ python-nav-beginning-of-defun-3
                 (beginning-of-line)
                 (point))))))
 
+(ert-deftest python-nav-beginning-of-defun-4 ()
+  (python-tests-with-temp-buffer
+   "
+def \\
+        a():
+    return 0
+"
+   (python-tests-look-at "return 0")
+   (should (= (save-excursion
+                (python-nav-beginning-of-defun)
+                (point))
+              (save-excursion
+                (python-tests-look-at "def \\" -1)
+                (beginning-of-line)
+                (point))))))
+
 (ert-deftest python-nav-end-of-defun-1 ()
   (python-tests-with-temp-buffer
    "
@@ -1964,6 +1980,20 @@ python-nav-end-of-defun-2
                 (python-tests-look-at "return wrapped_f")
                 (line-beginning-position))))))
 
+(ert-deftest python-nav-end-of-defun-3 ()
+  (python-tests-with-temp-buffer
+   "
+def \\
+        a():
+    return 0
+"
+   (should (= (save-excursion
+                (python-tests-look-at "def \\")
+                (python-nav-end-of-defun)
+                (point))
+              (save-excursion
+                (point-max))))))
+
 (ert-deftest python-nav-backward-defun-1 ()
   (python-tests-with-temp-buffer
    "
@@ -2062,6 +2092,18 @@ python-nav-backward-defun-3
      (should (not (python-nav-backward-defun)))
      (should (= point (point))))))
 
+(ert-deftest python-nav-backward-defun-4 ()
+  (python-tests-with-temp-buffer
+   "
+def \\
+        a():
+    return 0
+"
+   (goto-char (point-max))
+   (should (= (save-excursion (python-nav-backward-defun))
+              (python-tests-look-at "def \\" -1)))
+   (should (not (python-nav-backward-defun)))))
+
 (ert-deftest python-nav-forward-defun-1 ()
   (python-tests-with-temp-buffer
    "
@@ -2160,6 +2202,18 @@ python-nav-forward-defun-3
      (should (not (python-nav-forward-defun)))
      (should (= point (point))))))
 
+(ert-deftest python-nav-forward-defun-4 ()
+  (python-tests-with-temp-buffer
+   "
+def \\
+        a():
+    return 0
+"
+   (goto-char (point-min))
+   (should (= (save-excursion (python-nav-forward-defun))
+              (python-tests-look-at "():")))
+   (should (not (python-nav-forward-defun)))))
+
 (ert-deftest python-nav-beginning-of-statement-1 ()
   (python-tests-with-temp-buffer
    "