Segment.split_cells fix

CHANGELOG.md

@@ -5,11 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## Unreleased
+## [13.9.2] - 2024-10-04
 
 ### Fixed
 
 - Fixed `Table` columns not highlighting when added by `add_row` https://github.com/Textualize/rich/issues/3517
+- Fixed an issue with Segment.split_cells reported in Textual https://github.com/Textualize/textual/issues/5090
 
 ## [13.9.1] - 2024-10-01
 
@@ -2096,6 +2097,7 @@ Major version bump for a breaking change to `Text.stylize signature`, which corr
 
 - First official release, API still to be stabilized
 
+[13.9.2]: https://github.com/textualize/rich/compare/v13.9.1...v13.9.2
 [13.9.1]: https://github.com/textualize/rich/compare/v13.9.0...v13.9.1
 [13.9.0]: https://github.com/textualize/rich/compare/v13.8.1...v13.9.0
 [13.8.1]: https://github.com/textualize/rich/compare/v13.8.0...v13.8.1

pyproject.toml

@@ -2,7 +2,7 @@
 name = "rich"
 homepage = "https://github.com/Textualize/rich"
 documentation = "https://rich.readthedocs.io/en/latest/"
-version = "13.9.1"
+version = "13.9.2"
 description = "Render rich text, tables, progress bars, syntax highlighting, markdown and more to the terminal"
 authors = ["Will McGugan <[email protected]>"]
 license = "MIT"

rich/segment.py

@@ -129,34 +129,31 @@ def _split_cells(cls, segment: "Segment", cut: int) -> Tuple["Segment", "Segment
 
         cell_size = get_character_cell_size
 
-        pos = int((cut / cell_length) * (len(text))) - 1
-        if pos < 0:
-            pos = 0
+        pos = int((cut / cell_length) * len(text))
 
-        before = text[:pos]
-        cell_pos = cell_len(before)
-        if cell_pos == cut:
-            return (
-                _Segment(before, style, control),
-                _Segment(text[pos:], style, control),
-            )
-        while pos < len(text):
-            char = text[pos]
-            pos += 1
-            cell_pos += cell_size(char)
+        while True:
             before = text[:pos]
-            if cell_pos == cut:
+            cell_pos = cell_len(before)
+            out_by = cell_pos - cut
+            if not out_by:
                 return (
                     _Segment(before, style, control),
                     _Segment(text[pos:], style, control),
                 )
-            if cell_pos > cut:
+            if out_by == -1 and cell_size(text[pos]) == 2:
                 return (
-                    _Segment(before[: pos - 1] + " ", style, control),
+                    _Segment(text[:pos] + " ", style, control),
+                    _Segment(" " + text[pos + 1 :], style, control),
+                )
+            if out_by == +1 and cell_size(text[pos - 1]) == 2:
+                return (
+                    _Segment(text[: pos - 1] + " ", style, control),
                     _Segment(" " + text[pos:], style, control),
                 )
-
-        raise AssertionError("Will never reach here")
+            if cell_pos < cut:
+                pos += 1
+            else:
+                pos -= 1
 
     def split_cells(self, cut: int) -> Tuple["Segment", "Segment"]:
         """Split segment in to two segments at the specified column.

tests/test_segment.py

@@ -285,14 +285,30 @@ def test_split_cells_emoji(text, split, result):
     assert Segment(text).split_cells(split) == result
 
 
-def test_split_cells_mixed() -> None:
+@pytest.mark.parametrize(
+    "segment",
+    [
+        Segment("早乙女リリエル (CV: 徳井青）"),
+        Segment("メイド・イン・きゅんクチュアリ☆    "),
+        Segment("TVアニメ「メルクストーリア -無気力少年と瓶の中の少女-」 主題歌CD"),
+        Segment("南無阿弥JKうらめしや?！     "),
+        Segment("メルク (CV: 水瀬いのり)     "),
+        Segment(" メルク (CV: 水瀬いのり)     "),
+        Segment("  メルク (CV: 水瀬いのり)     "),
+        Segment("  メルク (CV: 水瀬いのり)      "),
+    ],
+)
+def test_split_cells_mixed(segment: Segment) -> None:
     """Check that split cells splits on cell positions."""
     # Caused https://github.com/Textualize/textual/issues/4996 in Textual
-    test = Segment("早乙女リリエル (CV: 徳井青）")
-    for position in range(1, test.cell_length):
-        left, right = Segment.split_cells(test, position)
+
+    for position in range(0, segment.cell_length + 1):
+        left, right = Segment.split_cells(segment, position)
+        assert all(
+            cell_len(c) > 0 for c in segment.text
+        )  # Sanity check there aren't any sneaky control codes
         assert cell_len(left.text) == position
-        assert cell_len(right.text) == test.cell_length - position
+        assert cell_len(right.text) == segment.cell_length - position
 
 
 def test_split_cells_doubles() -> None: