bug#71093: 30.0.50; python: multiple assignments not fontified

[kobarity <kobarity@gmail.com>]

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Eli Zaretskii wrote:
> 
> > Date: Tue, 21 May 2024 12:47:57 +0200
> > From: Andreas Röhler <andreas.roehler@easy-emacs.de>
> > 
> > a = b = c = 5
> > 
> > b and c are not fontified
> 
> Can someone please look into fixing this?  python-ts-mode does TRT,
> btw.

Sorry, this bug was introduced by my commit
4915ca5dd4245a909c046e6691e8d4a1919890c8.  I canceled it in commit
6b2c8dc9050c5c0514fa404733ce1d4a37d00e39 due to a performance issue,
but the cancellation was incomplete.  Attached is the patch to fix
this in master with an ERT.  Is it better to fix in emacs-29?

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From 0476507cc1fb77217fe051f6261c9a9a1d38243c Mon Sep 17 00:00:00 2001
From: kobarity <kobarity@gmail.com>
Date: Fri, 24 May 2024 21:00:59 +0900
Subject: [PATCH] Fix Python font lock of chained assignment statement

* lisp/progmodes/python.el
(python-font-lock-keywords-maximum-decoration): Allow chaining of single
assignment statements.
* test/lisp/progmodes/python-tests.el
(python-font-lock-assignment-statement-20): New test. (Bug#71093)
---
 lisp/progmodes/python.el            |  3 +--
 test/lisp/progmodes/python-tests.el | 10 ++++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 360936c9efd..fea52b2f7d6 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -800,8 +800,7 @@ python-font-lock-keywords-maximum-decoration
     ;;   c: Collection = {1, 2, 3}
     ;;   d: Mapping[int, str] = {1: 'bar', 2: 'baz'}
     (,(python-font-lock-assignment-matcher
-       (python-rx (or line-start ?\;) (* space)
-                  grouped-assignment-target (* space)
+       (python-rx grouped-assignment-target (* space)
                   (? ?: (* space) (group (+ not-simple-operator)) (* space))
                   (group assignment-operator)))
      (1 font-lock-variable-name-face)
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index b19c5c31f16..de6a4316758 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -502,6 +502,16 @@ python-font-lock-assignment-statement-19
      (31 . font-lock-type-face) (40)
      (43 . font-lock-operator-face) (44))))
 
+(ert-deftest python-font-lock-assignment-statement-20 ()
+  (python-tests-assert-faces
+   "a = b = c = 1"
+   '((1 . font-lock-variable-name-face) (2)
+     (3 . font-lock-operator-face) (4)
+     (5 . font-lock-variable-name-face) (6)
+     (7 . font-lock-operator-face) (8)
+     (9 . font-lock-variable-name-face) (10)
+     (11 . font-lock-operator-face) (12))))
+
 (ert-deftest python-font-lock-operator-1 ()
   (python-tests-assert-faces
    "1 << 2 ** 3 == +4%-5|~6&7^8%9"
-- 
2.34.1