From dd4863ad55310b084839df8f508bf57364d489b7 Mon Sep 17 00:00:00 2001
From: Denis Zubarev <dvzubarev@yandex.ru>
Date: Sat, 11 Nov 2023 04:55:44 +0300
Subject: [PATCH] Improve syntax highlighting for python-ts-mode

Fix fontification of strings inside of f-strings interpolation, e.g. for
f"beg {'nested'}" - 'nested' was not fontified as string.  Do not
override the face of builtin functions (all, bytes etc.) with the
function call face.  Add missing assignment expressions (:= *=).
Highlight variables defined in for loop (for var1, var2 in ).  Fontify
built-ins (dict,list,etc.) as types when they are used in type hints.
Highlight union types (type1|type2).  Highlight base class names in the
class definition.  Fontify class patterns in case statement. Highlight
the second argument as a type in isinstance/issubclass call. Highlight
dotted decorator names.

* lisp/progmodes/python.el (python--treesit-keywords): Add compound
keyword "is not".
(python--treesit-fontify-string): fix f-string interpolation. Enable
interpolation highlighting only if string-interpolation is presented on
the enabled levels of treesit-font-lock-feature-list.
(python--treesit-fontify-string-interpolation): Remove function.
(python--treesit-fontify-union-types): Fontify nested union types.
(python--treesit-fontify-dotted-decorator): Fontify all parts of
dotted decorator name.
(python--treesit-settings): Change/add rules.
* test/lisp/progmodes/python-tests.el (python-ts-tests-with-temp-buffer):
function for setting up test buffer.
(python-ts-mode-compound-keywords-face)
(python-ts-mode-var-for-loop-face)
(python-ts-mode-named-assignement-face-1)
(python-ts-mode-assignement-face-2)
(python-ts-mode-nested-types-face-1)
(python-ts-mode-union-types-face-1)
(python-ts-mode-union-types-face-2)
(python-ts-mode-types-face-1)
(python-ts-mode-types-face-2)
(python-ts-mode-types-face-3)
(python-ts-mode-isinstance-type-face-1)
(python-ts-mode-isinstance-type-face-2)
(python-ts-mode-superclass-type-face)
(python-ts-mode-class-patterns-face)
(python-ts-mode-dotted-decorator-face-1)
(python-ts-mode-dotted-decorator-face-2)
(python-ts-mode-builtin-call-face)
(python-ts-mode-interpolation-nested-string)
(python-ts-mode-disabled-string-interpolation)
(python-ts-mode-interpolation-doc-string): Add tests.
---
 lisp/progmodes/python.el            | 183 +++++++++++++-----
 test/lisp/progmodes/python-tests.el | 285 ++++++++++++++++++++++++++++
 2 files changed, 420 insertions(+), 48 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index ab3bf1b4ec..1b33a45965 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -979,7 +979,7 @@ python--treesit-keywords
     "raise" "return" "try" "while" "with" "yield"
     ;; These are technically operators, but we fontify them as
     ;; keywords.
-    "and" "in" "is" "not" "or" "not in"))
+    "and" "in" "is" "not" "or" "not in" "is not"))
 
 (defvar python--treesit-builtins
   '("abs" "all" "any" "ascii" "bin" "bool" "breakpoint" "bytearray"
@@ -1042,9 +1042,7 @@ python--treesit-fontify-string
 f-strings.  OVERRIDE is the override flag described in
 `treesit-font-lock-rules'.  START and END mark the region to be
 fontified."
-  (let* ((string-beg (treesit-node-start node))
-         (string-end (treesit-node-end node))
-         (maybe-expression (treesit-node-parent node))
+  (let* ((maybe-expression (treesit-node-parent node))
          (grandparent (treesit-node-parent
                        (treesit-node-parent
                         maybe-expression)))
@@ -1072,28 +1070,78 @@ python--treesit-fontify-string
                         (equal (treesit-node-type maybe-expression)
                                "expression_statement"))
                    'font-lock-doc-face
-                 'font-lock-string-face)))
-    ;; Don't highlight string prefixes like f/r/b.
-    (save-excursion
-      (goto-char string-beg)
-      (when (re-search-forward "[\"']" string-end t)
-        (setq string-beg (match-beginning 0))))
-    (treesit-fontify-with-override
-     string-beg string-end face override start end)))
-
-(defun python--treesit-fontify-string-interpolation
-    (node _ start end &rest _)
-  "Fontify string interpolation.
-NODE is the string node.  Do not fontify the initial f for
-f-strings.  START and END mark the region to be
+                 'font-lock-string-face))
+
+         (ignore-interpolation (not
+                                (seq-some
+                                 (lambda (feats) (memq 'string-interpolation feats))
+                                 (seq-take treesit-font-lock-feature-list treesit-font-lock-level))))
+         ;; If interpolation is enabled, highlight only
+         ;; string_start/string_content/string_end children.  Do not
+         ;; touch interpolation node that can occur inside of the
+         ;; string.
+         (string-nodes (if ignore-interpolation
+                           (list node)
+                         (treesit-filter-child
+                          node
+                          (lambda (ch) (member (treesit-node-type ch)
+                                               '("string_start"
+                                                 "string_content"
+                                                 "string_end")))
+                          t))))
+
+    (dolist (string-node string-nodes)
+      (let ((string-beg (treesit-node-start string-node))
+            (string-end (treesit-node-end string-node)))
+        (when (or ignore-interpolation
+                  (equal (treesit-node-type string-node) "string_start"))
+          ;; Don't highlight string prefixes like f/r/b.
+          (save-excursion
+            (goto-char string-beg)
+            (when (re-search-forward "[\"']" string-end t)
+              (setq string-beg (match-beginning 0)))))
+
+        (treesit-fontify-with-override
+         string-beg string-end face override start end)))))
+
+(defun python--treesit-fontify-union-types (node override start end &rest _)
+  "Fontify nested union types in the type hints.
+For examlpe, Lvl1 | Lvl2[Lvl3[Lvl4[Lvl5 | None]], Lvl2].  This
+structure is represented via nesting binary_operator and
+subscript nodes.  This function iterates over all levels and
+highlight identifier nodes.  NODE is the binary_operator
+node.  OVERRIDE is the override flag described in
+`treesit-font-lock-rules'.  START and END mark the region to be
 fontified."
-  ;; This is kind of a hack, it basically removes the face applied by
-  ;; the string feature, so that following features can apply their
-  ;; face.
-  (let ((n-start (treesit-node-start node))
-        (n-end (treesit-node-end node)))
-    (remove-text-properties
-     (max start n-start) (min end n-end) '(face))))
+  (dolist (child (treesit-node-children node t))
+    (pcase (treesit-node-type child)
+      ((or "identifier" "none")
+       (treesit-fontify-with-override
+        (treesit-node-start child) (treesit-node-end child)
+        'font-lock-type-face override start end))
+      ("attribute"
+       (when-let ((type-node (treesit-node-child-by-field-name child "attribute")))
+         (treesit-fontify-with-override
+          (treesit-node-start type-node) (treesit-node-end type-node)
+          'font-lock-type-face override start end)))
+      ((or "binary_operator" "subscript")
+       (python--treesit-fontify-union-types child override start end)))))
+
+(defun python--treesit-fontify-dotted-decorator (node override start end &rest _)
+  "Fontify dotted decorators.
+For example @pytes.mark.skip.  Iterate over all nested attribute
+nodes and highlight identifier nodes.  NODE is the first attribute
+node.  OVERRIDE is the override flag described in
+`treesit-font-lock-rules'.  START and END mark the region to be
+fontified."
+  (dolist (child (treesit-node-children node t))
+    (pcase (treesit-node-type child)
+      ("identifier"
+       (treesit-fontify-with-override
+        (treesit-node-start child) (treesit-node-end child)
+        'font-lock-type-face override start end))
+      ("attribute"
+       (python--treesit-fontify-dotted-decorator child override start end)))))
 
 (defvar python--treesit-settings
   (treesit-font-lock-rules
@@ -1103,14 +1151,9 @@ python--treesit-settings
 
    :feature 'string
    :language 'python
-   '((string) @python--treesit-fontify-string)
+   '((string) @python--treesit-fontify-string
+     (interpolation ["{" "}"] @font-lock-misc-punctuation-face))
 
-   ;; HACK: This feature must come after the string feature and before
-   ;; other features.  Maybe we should make string-interpolation an
-   ;; option rather than a feature.
-   :feature 'string-interpolation
-   :language 'python
-   '((interpolation) @python--treesit-fontify-string-interpolation)
 
    :feature 'keyword
    :language 'python
@@ -1126,12 +1169,6 @@ python--treesit-settings
       name: (identifier) @font-lock-type-face)
      (parameters (identifier) @font-lock-variable-name-face))
 
-   :feature 'function
-   :language 'python
-   '((call function: (identifier) @font-lock-function-call-face)
-     (call function: (attribute
-                      attribute: (identifier) @font-lock-function-call-face)))
-
    :feature 'builtin
    :language 'python
    `(((identifier) @font-lock-builtin-face
@@ -1142,6 +1179,12 @@ python--treesit-settings
                       eol))
               @font-lock-builtin-face)))
 
+   :feature 'function
+   :language 'python
+   '((call function: (identifier) @font-lock-function-call-face)
+     (call function: (attribute
+                      attribute: (identifier) @font-lock-function-call-face)))
+
    :feature 'constant
    :language 'python
    '([(true) (false) (none)] @font-lock-constant-face)
@@ -1153,30 +1196,74 @@ python--treesit-settings
                  @font-lock-variable-name-face)
      (assignment left: (attribute
                         attribute: (identifier)
-                        @font-lock-property-use-face))
-     (pattern_list (identifier)
+                        @font-lock-variable-name-face))
+     (augmented_assignment left: (identifier)
+                           @font-lock-variable-name-face)
+     (named_expression name: (identifier)
+                       @font-lock-variable-name-face)
+     (pattern_list [(identifier)
+                    (list_splat_pattern (identifier))]
                    @font-lock-variable-name-face)
-     (tuple_pattern (identifier)
+     (tuple_pattern [(identifier)
+                     (list_splat_pattern (identifier))]
                     @font-lock-variable-name-face)
-     (list_pattern (identifier)
-                   @font-lock-variable-name-face)
-     (list_splat_pattern (identifier)
-                         @font-lock-variable-name-face))
+     (list_pattern [(identifier)
+                    (list_splat_pattern (identifier))]
+                   @font-lock-variable-name-face))
 
    :feature 'decorator
    :language 'python
+   ;; Override function call face.
+   :override t
    '((decorator "@" @font-lock-type-face)
      (decorator (call function: (identifier) @font-lock-type-face))
-     (decorator (identifier) @font-lock-type-face))
+     (decorator (identifier) @font-lock-type-face)
+     (decorator [(attribute) (call (attribute))] @python--treesit-fontify-dotted-decorator))
 
    :feature 'type
    :language 'python
+   ;; Override built-in faces when dict/list are used for type hints.
+   :override t
    `(((identifier) @font-lock-type-face
       (:match ,(rx-to-string
                 `(seq bol (or ,@python--treesit-exceptions)
-                      eol))
+                  eol))
               @font-lock-type-face))
-     (type (identifier) @font-lock-type-face))
+     (type [(identifier) (none)] @font-lock-type-face)
+     (type (attribute attribute: (identifier) @font-lock-type-face))
+     ;; We don't want to highlight a package of the type
+     ;; (e.g. pack.ClassName).  So explicitly exclude patterns with
+     ;; attribute, since we handle dotted type name in the previous
+     ;; rule.  The following rule handle
+     ;; generic_type/list/tuple/splat_type nodes.
+     (type (_ !attribute [[(identifier) (none)] @font-lock-type-face
+                          (attribute attribute: (identifier) @font-lock-type-face) ]))
+     ;; collections.abc.Iterator[T] case.
+     (type (subscript (attribute attribute: (identifier) @font-lock-type-face)))
+     ;; Nested optional type hints, e.g. val: Lvl1 | Lvl2[Lvl3[Lvl4]].
+     (type (binary_operator) @python--treesit-fontify-union-types)
+     ;;class Type(Base1, Sequence[T]).
+     (class_definition
+      superclasses:
+      (argument_list [(identifier) @font-lock-type-face
+                      (attribute attribute: (identifier) @font-lock-type-face)
+                      (subscript (identifier) @font-lock-type-face)
+                      (subscript (attribute attribute: (identifier) @font-lock-type-face))]))
+
+     ;; Patern matching: case [str(), pack0.Type0()].  Take only the
+     ;; last identifier.
+     (class_pattern (dotted_name (identifier) @font-lock-type-face :anchor))
+
+
+     ;; Highlight the second argument as a type in isinstance/issubclass.
+     ((call function: (identifier) @func-name
+            (argument_list :anchor (_)
+                           [(identifier) @font-lock-type-face
+                            (attribute attribute: (identifier) @font-lock-type-face)
+                            (tuple (identifier) @font-lock-type-face)
+                            (tuple (attribute attribute: (identifier) @font-lock-type-face))
+                            (binary_operator) @python--treesit-fontify-union-types]))
+      (:match "^is\\(?:instance\\|subclass\\)$" @func-name)))
 
    :feature 'escape-sequence
    :language 'python
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index a44a11896f..fd4d593613 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -7299,6 +7299,291 @@ python-tests--flymake-command-output-pattern
                          "Unused import a.b.c (unused-import)"
                        "W0611: Unused import a.b.c (unused-import)"))))))
 
+;;; python-ts-mode font-lock tests
+
+(defmacro python-ts-tests-with-temp-buffer (contents &rest body)
+  "Create a `python-ts-mode' enabled temp buffer with CONTENTS.
+BODY is code to be executed within the temp buffer.  Point is
+always located at the beginning of buffer."
+  (declare (indent 1) (debug t))
+  `(with-temp-buffer
+     (skip-unless (treesit-ready-p 'python))
+     (require 'python)
+     (let ((python-indent-guess-indent-offset nil))
+       (python-ts-mode)
+       (setopt treesit-font-lock-level 3)
+       (insert ,contents)
+       (font-lock-ensure)
+       (goto-char (point-min))
+       ,@body)))
+
+(ert-deftest python-ts-mode-compound-keywords-face ()
+  (dolist (test '("is not" "not in"))
+    (python-ts-tests-with-temp-buffer
+     (concat "t " test " t")
+     (forward-to-word)
+     (should (eq (face-at-point) font-lock-keyword-face))
+     (forward-to-word)
+     (should (eq (face-at-point) font-lock-keyword-face)))))
+
+(ert-deftest python-ts-mode-named-assignement-face-1 ()
+  (python-ts-tests-with-temp-buffer
+   "var := 3"
+   (should (eq (face-at-point) font-lock-variable-name-face))))
+
+(ert-deftest python-ts-mode-assignement-face-2 ()
+  (python-ts-tests-with-temp-buffer
+   "var, *rest = call()"
+   (dolist (test '("var" "rest"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-variable-name-face))))
+
+  (python-ts-tests-with-temp-buffer
+   "def func(*args):"
+   (dolist (test '("args"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-variable-name-face))))))
+
+(ert-deftest python-ts-mode-nested-types-face-1 ()
+  (python-ts-tests-with-temp-buffer
+   "def func(v:dict[ list[ tuple[str] ], int | None] | None):"
+   (dolist (test '("dict" "list" "tuple" "str" "int" "None" "None"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-union-types-face-1 ()
+  (python-ts-tests-with-temp-buffer
+   "def f(val: tuple[tuple, list[Lvl1 | Lvl2[Lvl3[Lvl4[Lvl5 | None]], Lvl2]]]):"
+   (dolist (test '("tuple" "tuple" "list" "Lvl1" "Lvl2" "Lvl3" "Lvl4" "Lvl5" "None" "Lvl2"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-union-types-face-2 ()
+  (python-ts-tests-with-temp-buffer
+   "def f(val: Type0 | Type1[Type2, pack0.Type3] | pack1.pack2.Type4 | None):"
+   (dolist (test '("Type0" "Type1" "Type2" "Type3" "Type4" "None"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))
+
+   (goto-char (point-min))
+   (dolist (test '("pack0" "pack1" "pack2"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-type-face))))))
+
+(ert-deftest python-ts-mode-types-face-1 ()
+  (python-ts-tests-with-temp-buffer
+   "def f(val: Callable[[Type0], (Type1, Type2)]):"
+   (dolist (test '("Callable" "Type0" "Type1" "Type2"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-types-face-2 ()
+  (python-ts-tests-with-temp-buffer
+   "def annot3(val:pack0.Type0)->pack1.pack2.pack3.Type1:"
+   (dolist (test '("Type0" "Type1"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))
+   (goto-char (point-min))
+   (dolist (test '("pack0" "pack1" "pack2" "pack3"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-type-face))))))
+
+(ert-deftest python-ts-mode-types-face-3 ()
+  (python-ts-tests-with-temp-buffer
+   "def annot3(val:collections.abc.Iterator[Type0]):"
+   (dolist (test '("Iterator" "Type0"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))
+   (goto-char (point-min))
+   (dolist (test '("collections" "abc"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-type-face))))))
+
+(ert-deftest python-ts-mode-isinstance-type-face-1 ()
+  (python-ts-tests-with-temp-buffer
+   "isinstance(var1, pkg.Type0)
+    isinstance(var2, (str, dict, Type1, type(None)))
+    isinstance(var3, my_type())"
+
+   (dolist (test '("var1" "pkg" "var2" "type" "None" "var3" "my_type"))
+     (let ((case-fold-search nil))
+       (search-forward test))
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-type-face))))
+
+   (goto-char (point-min))
+   (dolist (test '("Type0" "str" "dict" "Type1"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-isinstance-type-face-2 ()
+  (python-ts-tests-with-temp-buffer
+   "issubclass(mytype, int|list|collections.abc.Iterable)"
+   (dolist (test '("int" "list" "Iterable"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-superclass-type-face ()
+  (python-ts-tests-with-temp-buffer
+   "class Temp(Base1, pack0.Base2,  Sequence[T1, T2]):"
+
+   (dolist (test '("Base1" "Base2" "Sequence" "T1" "T2"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))
+
+   (goto-char (point-min))
+   (dolist (test '("pack0"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-type-face))))))
+
+(ert-deftest python-ts-mode-class-patterns-face ()
+  (python-ts-tests-with-temp-buffer
+   "match tt:
+        case str():
+            pass
+        case [Type0() | bytes(b) | pack0.pack1.Type1()]:
+            pass
+        case {'i': int(i), 'f': float() as f}:
+            pass"
+
+   (dolist (test '("str" "Type0" "bytes" "Type1" "int" "float"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))
+
+   (goto-char (point-min))
+   (dolist (test '("pack0" "pack1"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-type-face))))))
+
+(ert-deftest python-ts-mode-dotted-decorator-face-1 ()
+  (python-ts-tests-with-temp-buffer
+   "@pytest.mark.skip
+    @pytest.mark.skip(reason='msg')
+    def test():"
+
+   (dolist (test '("pytest" "mark" "skip" "pytest" "mark" "skip"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-dotted-decorator-face-2 ()
+  (python-ts-tests-with-temp-buffer
+   "@pytest.mark.skip(reason='msg')
+    def test():"
+
+   (setopt treesit-font-lock-level 4)
+   (dolist (test '("pytest" "mark" "skip"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-type-face)))))
+
+(ert-deftest python-ts-mode-builtin-call-face ()
+  (python-ts-tests-with-temp-buffer
+   "all()"
+   ;; enable 'function' feature from 4th level
+   (setopt treesit-font-lock-level 4)
+   (should (eq (face-at-point) font-lock-builtin-face))))
+
+(ert-deftest python-ts-mode-interpolation-nested-string ()
+  (python-ts-tests-with-temp-buffer
+   "t = f\"beg {True + 'string'}\""
+
+   (search-forward "True")
+   (goto-char (match-beginning 0))
+   (should (eq (face-at-point) font-lock-constant-face))
+
+   (goto-char (point-min))
+   (dolist (test '("f" "{" "+" "}"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-string-face))))
+
+
+   (goto-char (point-min))
+   (dolist (test '("beg" "'string'" "\""))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-string-face)))))
+
+(ert-deftest python-ts-mode-level-fontification-wo-interpolation ()
+  (python-ts-tests-with-temp-buffer
+   "t = f\"beg {True + var}\""
+
+   (setopt treesit-font-lock-level 2)
+   (search-forward "f")
+   (goto-char (match-beginning 0))
+   (should (not (eq (face-at-point) font-lock-string-face)))
+
+   (dolist (test '("\"" "beg" "{" "True" "var" "}" "\""))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-string-face)))))
+
+(ert-deftest python-ts-mode-disabled-string-interpolation ()
+  (python-ts-tests-with-temp-buffer
+   "t = f\"beg {True + var}\""
+
+   (unwind-protect
+       (progn
+         (setf (nth 2 treesit-font-lock-feature-list)
+               (remq 'string-interpolation (nth 2 treesit-font-lock-feature-list)))
+         (setopt treesit-font-lock-level 3)
+
+         (search-forward "f")
+         (goto-char (match-beginning 0))
+         (should (not (eq (face-at-point) font-lock-string-face)))
+
+         (dolist (test '("\"" "beg" "{" "True" "var" "}" "\""))
+           (search-forward test)
+           (goto-char (match-beginning 0))
+           (should (eq (face-at-point) font-lock-string-face))))
+
+    (setf (nth 2 treesit-font-lock-feature-list)
+          (append (nth 2 treesit-font-lock-feature-list) '(string-interpolation))))))
+
+(ert-deftest python-ts-mode-interpolation-doc-string ()
+  (python-ts-tests-with-temp-buffer
+   "f\"\"\"beg {'s1' + True + 's2'} end\"\"\""
+
+   (search-forward "True")
+   (goto-char (match-beginning 0))
+   (should (eq (face-at-point) font-lock-constant-face))
+
+   (goto-char (point-min))
+   (dolist (test '("f" "{" "+" "}"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (not (eq (face-at-point) font-lock-string-face))))
+
+   (goto-char (point-min))
+   (dolist (test '("\"\"\"" "beg" "end" "\"\"\""))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-doc-face)))
+
+   (goto-char (point-min))
+   (dolist (test '("'s1'" "'s2'"))
+     (search-forward test)
+     (goto-char (match-beginning 0))
+     (should (eq (face-at-point) font-lock-string-face)))))
+
 (provide 'python-tests)
 
 ;;; python-tests.el ends here
-- 
2.34.1