bug#55702: 29.0.50; python-mark-defun does not handle backslash escaped newline

[kobarity <kobarity@gmail.com>]

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python-mark-defun and python-info-looking-at-beginning-of-defun do not
consider the presence of backslash escaped newline in defuns.
Attached is a patch to fix this issue.

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commit 28aeb41bc05ecf2d887a8d9290f860e52ee4e73e
Author: kobarity <kobarity@gmail.com>
Date:   Sun May 29 21:23:35 2022 +0900

    Make `python-mark-defun' handle backslash escaped newline
    
    * lisp/progmodes/python.el (python-mark-defun)
    (python-info-looking-at-beginning-of-defun): Allow backslash
    escaped newline in defuns (bug#55702).

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index c2483436fe..7ab063daa9 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -1426,7 +1426,7 @@ python-mark-defun
 marks the next defun after the ones already marked."
   (interactive "p")
   (when (python-info-looking-at-beginning-of-defun)
-    (end-of-line 1))
+    (python-nav-end-of-statement))
   (mark-defun allow-extend))
 
 \f
@@ -5290,6 +5290,7 @@ python-info-looking-at-beginning-of-defun
   "Check if point is at `beginning-of-defun' using SYNTAX-PPSS."
   (and (not (python-syntax-context-type (or syntax-ppss (syntax-ppss))))
        (save-excursion
+         (python-nav-beginning-of-statement)
          (beginning-of-line 1)
          (looking-at python-nav-beginning-of-defun-regexp))))
 
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index 8db0a07170..c1b71d15fd 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -1736,6 +1736,36 @@ python-mark-defun-3
      (should (= (marker-position (mark-marker))
                 expected-mark-end-position)))))
 
+(ert-deftest python-mark-defun-4 ()
+  "Test `python-mark-defun' with point inside backslash escaped defun."
+  (python-tests-with-temp-buffer
+   "
+def \\
+        foo(x):
+    return x
+"
+   (let ((transient-mark-mode t)
+         (expected-mark-beginning-position
+          (progn
+            (python-tests-look-at "def ")
+            (1- (line-beginning-position))))
+         (expected-mark-end-position
+          (save-excursion
+            (python-tests-look-at "return x")
+            (forward-line)
+            (point))))
+     (python-tests-look-at "def ")
+     (python-mark-defun 1)
+     (should (= (point) expected-mark-beginning-position))
+     (should (= (marker-position (mark-marker))
+                expected-mark-end-position))
+     (deactivate-mark)
+     (python-tests-look-at "foo(x)")
+     (python-mark-defun 1)
+     (should (= (point) expected-mark-beginning-position))
+     (should (= (marker-position (mark-marker))
+                expected-mark-end-position)))))
+
 \f
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