From a8acb9516e75b9b13ee988b6cbc2e6bbe1aa531c Mon Sep 17 00:00:00 2001
From: kobarity <kobarity@gmail.com>
Date: Sat, 21 May 2022 15:23:21 +0200
Subject: [PATCH] Fix recently introduced Python font lock breakage of chained
 assignments

* lisp/progmodes/python.el (python-font-lock-assignment-matcher):
Fix fontification of chained assignments (bug#54992).
---
 lisp/progmodes/python.el            | 9 ++++++---
 test/lisp/progmodes/python-tests.el | 7 +++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index ca744b1cfde..0761aaebdcc 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -606,12 +606,15 @@ builtins.")
 Search for next occurrence if REGEXP matched within a `paren'
 context (to avoid, e.g., default values for arguments or passing
 arguments by name being treated as assignments) or is followed by
-an '=' sign (to avoid '==' being treated as an assignment."
+an '=' sign (to avoid '==' being treated as an assignment.  Set
+point to the position one character before the end of the
+occurrence found so that subsequent searches can detect the '='
+sign in chained assignment."
   (lambda (limit)
     (cl-loop while (re-search-forward regexp limit t)
              unless (or (python-syntax-context 'paren)
                         (equal (char-after) ?=))
-               return t)))
+               return (progn (backward-char) t))))
 
 (defvar python-font-lock-keywords-maximum-decoration
   `((python--font-lock-f-strings)
@@ -706,7 +709,7 @@ an '=' sign (to avoid '==' being treated as an assignment."
     ;;   [a] = 5
     ;;   [*a] = 5, 6
     (,(python-font-lock-assignment-matcher
-       (python-rx (or line-start ?\;) (* space)
+       (python-rx (or line-start ?\; ?=) (* space)
                   (or "[" "(") (* space)
                   grouped-assignment-target (* space)
                   (or ")" "]") (* space)
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index 98b55a5f8bc..ee7b66610aa 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -342,6 +342,13 @@ aliqua."
      (16 . font-lock-variable-name-face) (17))))
 
 (ert-deftest python-font-lock-assignment-statement-17 ()
+  (python-tests-assert-faces
+   "(a) = (b) = 1"
+   `((1)
+     (2 . font-lock-variable-name-face) (3)
+     (8 . font-lock-variable-name-face) (9))))
+
+(ert-deftest python-font-lock-assignment-statement-18 ()
   (python-tests-assert-faces
    "CustomInt = int
 
-- 
2.39.2