gh-138318, PyREPL: builtins should not be highlighted when used as attribute names

Lib/_pyrepl/utils.py

@@ -208,7 +208,10 @@ def gen_colors_from_token_stream(
                 ):
                     span = Span.from_token(token, line_lengths)
                     yield ColorSpan(span, "soft_keyword")
-                elif token.string in BUILTINS:
+                elif (
+                    token.string in BUILTINS
+                    and not (prev_token and prev_token.exact_type == T.DOT)
+                ):
                     span = Span.from_token(token, line_lengths)
                     yield ColorSpan(span, "builtin")
 

Lib/test/test_pyrepl/test_utils.py

@@ -1,6 +1,6 @@
 from unittest import TestCase
 
-from _pyrepl.utils import str_width, wlen, prev_next_window
+from _pyrepl.utils import str_width, wlen, prev_next_window, gen_colors
 
 
 class TestUtils(TestCase):
@@ -60,3 +60,24 @@ def gen_raise():
         self.assertEqual(next(pnw), (3, 4, None))
         with self.assertRaises(ZeroDivisionError):
             next(pnw)
+
+    def test_gen_colors_keyword_highlighting(self):
+        cases = [
+            # no highlights
+            ("a.set", [(".", "op")]),
+            ("obj.list", [(".", "op")]),
+            ("obj.match", [(".", "op")]),
+            ("b. \\\n format", [(".", "op")]),
+            # highlights
+            ("set", [("set", "builtin")]),
+            ("list", [("list", "builtin")]),
+        ]
+        for code, expected_highlights in cases:
+            with self.subTest(code=code):
+                colors = list(gen_colors(code))
+                # Extract (text, tag) pairs for comparison
+                actual_highlights = []
+                for color in colors:
+                    span_text = code[color.span.start:color.span.end + 1]
+                    actual_highlights.append((span_text, color.tag))
+                self.assertEqual(actual_highlights, expected_highlights)

Misc/NEWS.d/next/Core_and_Builtins/2025-09-01-16-09-02.gh-issue-138318.t-WEN5.rst

@@ -0,0 +1,4 @@
+The default REPL now avoids highlighting built-in names (for instance :class:`set`
+or :func:`format`) when they are used as attribute names (for instance in ``value.set``
+or ``text.format``).
+