Fix ANSI escape explosion when slicing ANSIString after reset

evennia/utils/ansi.py

@@ -1078,8 +1078,14 @@ class ANSIString(str, metaclass=ANSIMeta):
 
         code_indexes_set = set(self._code_indexes)
 
+        # Only collect codes after the last reset to avoid accumulating
+        # cancelled codes when slicing
+        start_pos = self._find_last_reset_before(char_pos)
+
         result_chars = [
-            self._raw_string[index] for index in range(0, char_pos + 1) if index in code_indexes_set
+            self._raw_string[index]
+            for index in range(start_pos, char_pos + 1)
+            if index in code_indexes_set
         ]
 
         result = "".join(result_chars)
@@ -1168,6 +1174,23 @@ class ANSIString(str, metaclass=ANSIMeta):
 
         return code_indexes, char_indexes
 
+    def _find_last_reset_before(self, pos):
+        """
+        Find the end position of the last ANSI reset sequence
+        that occurs before the given position.
+
+        Args:
+            pos (int): Position in _raw_string to search before.
+
+        Returns:
+            int: The index immediately after the last reset sequence,
+                 or 0 if no reset was found before pos.
+        """
+        reset_pos = self._raw_string.rfind(ANSI_NORMAL, 0, pos)
+        if reset_pos == -1:
+            return 0
+        return reset_pos + len(ANSI_NORMAL)
+
     def _get_interleving(self, index):
         """
         Get the code characters from the given slice end to the next

evennia/utils/tests/test_ansi.py

@@ -195,3 +195,35 @@ class TestANSIString(TestCase):
         self.assertEqual(plain.upper().clean(), "HELLO WORLD")
         self.assertEqual(plain.lower().clean(), "hello world")
         self.assertEqual(plain.capitalize().clean(), "Hello world")
+
+    def test_getitem_no_cancelled_codes_after_reset(self):
+        """
+        Test that slicing after a reset does NOT inherit cancelled codes.
+
+        This prevents exponential ANSI code accumulation during split/slice
+        operations. Text after a reset (|n) should not carry forward the
+        color codes that were cancelled by that reset.
+        """
+        # String with red text, reset, then plain text
+        text = AN("|rRed|n plain")
+
+        # Slice starting after the reset - should NOT have red codes
+        after_reset = text[4:]  # " plain"
+        self.assertEqual(after_reset.clean(), "plain")
+
+        # The raw output should NOT contain red color code since it was reset
+        raw = after_reset.raw()
+        self.assertNotIn(ANSI_RED, raw, "Cancelled red code should not appear after reset")
+        self.assertNotIn(ANSI_HILITE, raw, "Cancelled hilite code should not appear after reset")
+
+        # More complex case: multiple colors with resets
+        multi = AN("|rRed|n |gGreen|n |bBlue|n end")
+
+        # Slice after all color codes are reset
+        end_slice = multi[-3:]  # "end"
+        self.assertEqual(end_slice.clean(), "end")
+        # Should have no color codes since all were reset
+        end_raw = end_slice.raw()
+        self.assertNotIn(ANSI_RED, end_raw)
+        self.assertNotIn(ANSI_GREEN, end_raw)
+        self.assertNotIn(ANSI_BLUE, end_raw)

evennia/utils/tests/test_tagparsing.py

@@ -94,11 +94,12 @@ class ANSIStringTestCase(TestCase):
     def test_split(self):
         """
         Verifies that re.split and .split behave similarly and that color
-        codes end up where they should.
+        codes end up where they should, including across newlines.
         """
-        target = ANSIString("|gThis is |nA split string|g")
-        first = ("\x1b[1m\x1b[32mThis is \x1b[0m", "This is ")
-        second = ("\x1b[1m\x1b[32m\x1b[0m split string\x1b[1m\x1b[32m", " split string")
+        target = ANSIString("|gThis is \nA split string|g")
+        first = ("\x1b[1m\x1b[32mThis is \n", "This is \n")
+        # Color codes carry through the newline
+        second = ("\x1b[1m\x1b[32m split string\x1b[1m\x1b[32m", " split string")
         re_split = re.split("A", target)
         normal_split = target.split("A")
         self.assertEqual(re_split, normal_split)
@@ -219,19 +220,19 @@ class ANSIStringTestCase(TestCase):
 
     def test_slice_insert_longer(self):
         """
-        The ANSIString replays the color code before the split in order to
-        produce a *visually* identical result. The result is a longer string in
-        raw characters, but one which correctly represents the color output.
+        Test that slicing and inserting produces correct ANSI output,
+        with color codes preserved across newlines.
         """
-        string = ANSIString("A bigger |rTest|n of things |bwith more color|n")
-        # from evennia import set_trace;set_trace()
+        string = ANSIString("A bigger |rTest\n of things |bwith more color|n")
         split_string = string[:9] + "Test" + string[13:]
+        # string[:9] includes trailing red code since position 9 is in red region
+        # string[13:] carries red through the newline
         self.assertEqual(
             repr(
                 (
                     ANSIString("A bigger ")
-                    + ANSIString("|rTest")  # note that the |r|n is replayed together on next line
-                    + ANSIString("|r|n of things |bwith more color|n")
+                    + ANSIString("|rTest")
+                    + ANSIString("|r\n of things |bwith more color|n")
                 ).raw()
             ),
             repr(split_string.raw()),