Revert "Enhance Python font-lock to support multilines"

This reverts commit 4915ca5dd4.

We have found that there are performance issues when editing a large
file.  The issue can be reproduced as follows:

1. emacs -Q
2. Open large Python file (e.g. turtle.py in Python)
3. Near the top of the buffer, enter open paren and some characters.

The above commit extends the region to be font-locked using
`python-nav-end-of-statement'.  However, if there are unbalanced
parens, it may move point to the end of the buffer.  This causes
almost the entire buffer to be font-locked, which is not acceptable
for large files.

lisp/progmodes/python.el

@@ -415,7 +415,6 @@ instead."
   "Python mode specialized rx macro.
 This variant of `rx' supports common Python named REGEXPS."
   `(rx-let ((sp-bsnl (or space (and ?\\ ?\n)))
-            (sp-nl (or space (and (? ?\\) ?\n)))
             (block-start       (seq symbol-start
                                     (or "def" "class" "if" "elif" "else" "try"
                                         "except" "finally" "for" "while" "with"
@@ -650,9 +649,9 @@ the {...} holes that appear within f-strings."
              finally return (and result-valid result))))
 
 (defvar python-font-lock-keywords-level-1
-  `((,(python-rx symbol-start "def" (1+ sp-bsnl) (group symbol-name))
+  `((,(python-rx symbol-start "def" (1+ space) (group symbol-name))
      (1 font-lock-function-name-face))
-    (,(python-rx symbol-start "class" (1+ sp-bsnl) (group symbol-name))
+    (,(python-rx symbol-start "class" (1+ space) (group symbol-name))
      (1 font-lock-type-face)))
   "Font lock keywords to use in `python-mode' for level 1 decoration.
 
@@ -792,12 +791,12 @@ sign in chained assignment."
     ;;   [*a] = 5, 6
     ;; are handled separately below
     (,(python-font-lock-assignment-matcher
-        (python-rx (? (or "[" "(") (* sp-nl))
+        (python-rx (? (or "[" "(") (* space))
-                   grouped-assignment-target (* sp-nl) ?, (* sp-nl)
+                   grouped-assignment-target (* space) ?, (* space)
-                   (* assignment-target (* sp-nl) ?, (* sp-nl))
+                   (* assignment-target (* space) ?, (* space))
-                   (? assignment-target (* sp-nl))
+                   (? assignment-target (* space))
-                   (? ?, (* sp-nl))
+                   (? ?, (* space))
-                   (? (or ")" "]") (* sp-bsnl))
+                   (? (or ")" "]") (* space))
                    (group assignment-operator)))
      (1 font-lock-variable-name-face)
      (2 'font-lock-operator-face)
@@ -813,9 +812,9 @@ sign in chained assignment."
     ;;   c: Collection = {1, 2, 3}
     ;;   d: Mapping[int, str] = {1: 'bar', 2: 'baz'}
     (,(python-font-lock-assignment-matcher
-       (python-rx (or line-start ?\;) (* sp-bsnl)
+       (python-rx (or line-start ?\;) (* space)
-                  grouped-assignment-target (* sp-bsnl)
+                  grouped-assignment-target (* space)
-                  (? ?: (* sp-bsnl) (+ not-simple-operator) (* sp-bsnl))
+                  (? ?: (* space) (+ not-simple-operator) (* space))
                   (group assignment-operator)))
      (1 font-lock-variable-name-face)
      (2 'font-lock-operator-face))
@@ -824,10 +823,10 @@ sign in chained assignment."
     ;;   [a] = 5,
     ;;   [*a] = 5, 6
     (,(python-font-lock-assignment-matcher
-       (python-rx (or line-start ?\; ?=) (* sp-bsnl)
+       (python-rx (or line-start ?\; ?=) (* space)
-                  (or "[" "(") (* sp-nl)
+                  (or "[" "(") (* space)
-                  grouped-assignment-target (* sp-nl)
+                  grouped-assignment-target (* space)
-                  (or ")" "]") (* sp-bsnl)
+                  (or ")" "]") (* space)
                   (group assignment-operator)))
      (1 font-lock-variable-name-face)
      (2 'font-lock-operator-face))
@@ -869,22 +868,6 @@ decorators, exceptions, and assignments.")
 Which one will be chosen depends on the value of
 `font-lock-maximum-decoration'.")
 
-(defvar font-lock-beg)
-(defvar font-lock-end)
-(defun python-font-lock-extend-region ()
-  "Extend font-lock region to statement boundaries."
-  (let ((beg font-lock-beg)
-        (end font-lock-end))
-    (goto-char beg)
-    (python-nav-beginning-of-statement)
-    (beginning-of-line)
-    (when (< (point) beg)
-      (setq font-lock-beg (point)))
-    (goto-char end)
-    (python-nav-end-of-statement)
-    (when (< end (point))
-      (setq font-lock-end (point)))
-    (or (/= beg font-lock-beg) (/= end font-lock-end))))
 
 (defconst python-syntax-propertize-function
   (syntax-propertize-rules
@@ -6709,8 +6692,6 @@ implementations: `python-mode' and `python-ts-mode'."
                 nil nil nil nil
                 (font-lock-syntactic-face-function
                  . python-font-lock-syntactic-face-function)))
-  (add-hook 'font-lock-extend-region-functions
-            #'python-font-lock-extend-region nil t)
   (setq-local syntax-propertize-function
               python-syntax-propertize-function)
   (setq-local imenu-create-index-function

test/lisp/progmodes/python-tests.el

@@ -136,20 +136,6 @@ STRING, it is skipped so the next STRING occurrence is selected."
            while pos
            collect (cons pos (get-text-property pos 'face))))
 
-(defun python-tests-assert-faces-after-change (content faces search replace)
-  "Assert that font faces for CONTENT are equal to FACES after change.
-All occurrences of SEARCH are changed to REPLACE."
-  (python-tests-with-temp-buffer
-   content
-   ;; Force enable font-lock mode without jit-lock.
-   (rename-buffer "*python-font-lock-test*" t)
-   (let (noninteractive font-lock-support-mode)
-     (font-lock-mode))
-   (while
-       (re-search-forward search nil t)
-     (replace-match replace))
-   (should (equal faces (python-tests-get-buffer-faces)))))
-
 (defun python-tests-self-insert (char-or-str)
   "Call `self-insert-command' for chars in CHAR-OR-STR."
   (let ((chars
@@ -297,13 +283,6 @@ p = (1 + 2)
    "def 1func():"
    '((1 . font-lock-keyword-face) (4))))
 
-(ert-deftest python-font-lock-keywords-level-1-3 ()
-  (python-tests-assert-faces
-   "def \\
-        func():"
-   '((1 . font-lock-keyword-face) (4)
-     (15 . font-lock-function-name-face) (19))))
-
 (ert-deftest python-font-lock-assignment-statement-1 ()
   (python-tests-assert-faces
    "a, b, c = 1, 2, 3"
@@ -495,129 +474,6 @@ def f(x: CustomInt) -> CustomInt:
      (136 . font-lock-operator-face) (137)
      (144 . font-lock-keyword-face) (150))))
 
-(ert-deftest python-font-lock-assignment-statement-multiline-1 ()
-  (python-tests-assert-faces-after-change
-   "
-[
-    a,
-    b
-] # (
-    1,
-    2
-)
-"
-   '((1)
-     (8 . font-lock-variable-name-face) (9)
-     (15 . font-lock-variable-name-face) (16)
-     (19 . font-lock-operator-face) (20))
-   "#" "="))
-
-(ert-deftest python-font-lock-assignment-statement-multiline-2 ()
-  (python-tests-assert-faces-after-change
-   "
-[
-    *a
-] # 5, 6
-"
-   '((1)
-     (8 . font-lock-operator-face)
-     (9 . font-lock-variable-name-face) (10)
-     (13 . font-lock-operator-face) (14))
-   "#" "="))
-
-(ert-deftest python-font-lock-assignment-statement-multiline-3 ()
-  (python-tests-assert-faces-after-change
-   "a\\
-    ,\\
-    b\\
-    ,\\
-    c\\
-    #\\
-    1\\
-    ,\\
-    2\\
-    ,\\
-    3"
-   '((1 . font-lock-variable-name-face) (2)
-     (15 . font-lock-variable-name-face) (16)
-     (29 . font-lock-variable-name-face) (30)
-     (36 . font-lock-operator-face) (37))
-   "#" "="))
-
-(ert-deftest python-font-lock-assignment-statement-multiline-4 ()
-  (python-tests-assert-faces-after-change
-   "a\\
-    :\\
-    int\\
-    #\\
-    5"
-   '((1 . font-lock-variable-name-face) (2)
-     (15 . font-lock-builtin-face) (18)
-     (24 . font-lock-operator-face) (25))
-   "#" "="))
-
-(ert-deftest python-font-lock-assignment-statement-multiline-5 ()
-  (python-tests-assert-faces-after-change
-   "(\\
-    a\\
-)\\
-    #\\
-    5\\
-    ;\\
-    (\\
-    b\\
-    )\\
-    #\\
-    6"
-   '((1)
-     (8 . font-lock-variable-name-face) (9)
-     (18 . font-lock-operator-face) (19)
-     (46 . font-lock-variable-name-face) (47)
-     (60 . font-lock-operator-face) (61))
-   "#" "="))
-
-(ert-deftest python-font-lock-assignment-statement-multiline-6 ()
-  (python-tests-assert-faces-after-change
-   "(
-    a
-)\\
-    #\\
-    5\\
-    ;\\
-    (
-    b
-    )\\
-    #\\
-    6"
-   '((1)
-     (7 . font-lock-variable-name-face) (8)
-     (16 . font-lock-operator-face) (17)
-     (43 . font-lock-variable-name-face) (44)
-     (56 . font-lock-operator-face) (57))
-   "#" "="))
-
-(ert-deftest python-font-lock-operator-1 ()
-  (python-tests-assert-faces
-   "1 << 2 ** 3 == +4%-5|~6&7^8%9"
-   '((1)
-     (3 . font-lock-operator-face) (5)
-     (8 . font-lock-operator-face) (10)
-     (13 . font-lock-operator-face) (15)
-     (16 . font-lock-operator-face) (17)
-     (18 . font-lock-operator-face) (20)
-     (21 . font-lock-operator-face) (23)
-     (24 . font-lock-operator-face) (25)
-     (26 . font-lock-operator-face) (27)
-     (28 . font-lock-operator-face) (29))))
-
-(ert-deftest python-font-lock-operator-2 ()
-  "Keyword operators are font-locked as keywords."
-  (python-tests-assert-faces
-   "is_ is None"
-   '((1)
-     (5 . font-lock-keyword-face) (7)
-     (8 . font-lock-constant-face))))
-
 (ert-deftest python-font-lock-escape-sequence-string-newline ()
   (python-tests-assert-faces
    "'\\n'