gh-133710: Enhance pyrepl auto-indent

Lib/_pyrepl/readline.py

@@ -40,6 +40,7 @@
 from .completing_reader import CompletingReader
 from .console import Console as ConsoleType
 from ._module_completer import ModuleCompleter, make_default_module_completer
+from .utils import gen_colors
 
 Console: type[ConsoleType]
 _error: tuple[type[Exception], ...] | type[Exception]
@@ -253,23 +254,22 @@ def _get_first_indentation(buffer: list[str]) -> str | None:
 
 
 def _should_auto_indent(buffer: list[str], pos: int) -> bool:
-    # check if last character before "pos" is a colon, ignoring
-    # whitespaces and comments.
-    last_char = None
-    while pos > 0:
-        pos -= 1
-        if last_char is None:
-            if buffer[pos] not in " \t\n#":  # ignore whitespaces and comments
-                last_char = buffer[pos]
-        else:
-            # even if we found a non-whitespace character before
-            # original pos, we keep going back until newline is reached
-            # to make sure we ignore comments
-            if buffer[pos] == "\n":
-                break
-            if buffer[pos] == "#":
-                last_char = None
-    return last_char == ":"
+    buffer_str = ''.join(buffer)
+    colors = tuple(gen_colors(buffer_str))
+    string_spans = tuple(c.span for c in colors if c.tag == "string")
+    comment_spans = tuple(c.span for c in colors if c.tag == "comment")
+    def in_span(i, spans):
+        return any(s.start <= i <= s.end for s in spans)
+    i = pos - 1
+    while i >= 0:
+        if buffer_str[i] in " \t\n":
+            i -= 1
+            continue
+        if in_span(i, string_spans) or in_span(i, comment_spans):
+            i -= 1
+            continue
+        break
+    return i >= 0 and buffer_str[i] == ":"
 
 
 class maybe_accept(commands.Command):

Lib/test/test_pyrepl/test_pyrepl.py

@@ -594,6 +594,27 @@ def test_auto_indent_with_comment(self):
         output = multiline_input(reader)
         self.assertEqual(output, output_code)
 
+        # fmt: off
+        events = itertools.chain(
+            code_to_events("def f():\n"),
+            [
+                Event(evt="key", data="backspace", raw=b"\x08"),
+            ],
+            code_to_events("# foo\npass\n\n")
+        )
+
+        output_code = (
+            "def f():\n"
+            "# foo\n"
+            "    pass\n"
+            "    "
+        )
+        # fmt: on
+
+        reader = self.prepare_reader(events)
+        output = multiline_input(reader)
+        self.assertEqual(output, output_code)
+
     def test_auto_indent_with_multicomment(self):
         # fmt: off
         events = code_to_events(
@@ -627,6 +648,43 @@ def test_auto_indent_ignore_comments(self):
         output = multiline_input(reader)
         self.assertEqual(output, output_code)
 
+    def test_dont_indent_hashtag(self):
+        # fmt: off
+        events = code_to_events(
+            "if ' ' == '#':\n"
+                "pass\n\n"
+        )
+
+        output_code = (
+            "if ' ' == '#':\n"
+            "    pass\n"
+            "    "
+        )
+        # fmt: on
+
+        reader = self.prepare_reader(events)
+        output = multiline_input(reader)
+        self.assertEqual(output, output_code)
+
+    def test_dont_indent_in_multiline_string(self):
+        # fmt: off
+        events = code_to_events(
+            "s = '''\n"
+            "Note:\n"
+            "'''\n\n"
+        )
+
+        output_code = (
+            "s = '''\n"
+            "Note:\n"
+            "'''"
+        )
+        # fmt: on
+
+        reader = self.prepare_reader(events)
+        output = multiline_input(reader)
+        self.assertEqual(output, output_code)
+
 
 class TestPyReplOutput(ScreenEqualMixin, TestCase):
     def prepare_reader(self, events):

Misc/NEWS.d/next/Library/2025-10-28-23-14-16.gh-issue-133710.BzRnmu.rst

@@ -0,0 +1 @@
+Enhance auto-indent in :mod:`!_pyrepl`.