resolved RESOLVED UNSUBMITTED PASS · None tool calls · 0 s · Textualize/rich
fix for infinite loop in split_graphemes Fix for https://github.com/Textualize/rich/issues/3958
| # | Tool | Arguments | Result |
|---|---|---|---|
| No trace captured. | |||
--- a/rich/cells.py
+++ b/rich/cells.py
@@ -161,14 +161,19 @@ def _cell_len(text: str, unicode_version: str) -> int:
def split_graphemes(
text: str, unicode_version: str = "auto"
) -> "tuple[list[CellSpan], int]":
- """Divide text into spans that define a single grapheme.
+ """Divide text into spans that define a single grapheme, and additionally return the cell length of the whole string.
+
+ The returned spans will cover every index in the string, with no gaps. It is possible for some graphemes to have a cell length of zero.
+ This can occur for nonsense strings like two zero width joiners, or for control codes that don't contribute to the grapheme size.
Args:
text: String to split.
unicode_version: Unicode version, `"auto"` to auto detect, `"latest"` for the latest unicode version.
Returns:
- List of spans.
+ A tuple of a list of *spans* and the cell length of the entire string. A span is a list of tuples
+ of three values consisting of (<START>, <END>, <CELL LENGTH>), where START and END are string indices,
+ and CELL LENGTH is the cell length of the single grapheme.
"""
cell_table = load_cell_table(unicode_version)
@@ -181,32 +186,48 @@ def split_graphemes(
SPECIAL = {"\u200d", "\ufe0f"}
while index < codepoint_count:
if (character := text[index]) in SPECIAL:
+ if not spans:
+ # ZWJ or variation selector at the beginning of the string doesn't really make sense.
+ # But handle it, we must.
+ spans.append((index, index := index + 1, 0))
+ continue
if character == "\u200d":
# zero width joiner
- index += 2
- if spans:
- start, _end, cell_length = spans[-1]
- spans[-1] = (start, index, cell_length)
- elif last_measured_character:
+ # The condition handles the case where a ZWJ is at the end of the string, and has nothing to join
+ index += 2 if index < (codepoint_count - 1) else 1
+ start, _end, cell_length = spans[-1]
+ spans[-1] = (start, index, cell_length)
+ else:
# variation selector 16
index += 1
- if spans:
+ if last_measured_character:
start, _end, cell_length = spans[-1]
if last_measured_character in cell_table.narrow_to_wide:
last_measured_character = None
cell_length += 1
total_width += 1
spans[-1] = (start, index, cell_length)
+ else:
+ # No previous character to change the size of.
+ # Shouldn't occur in practice.
+ # But handle it, we must.
+ start, _end, cell_length = spans[-1]
+ spans[-1] = (start, index, cell_length)
continue
if character_width := get_character_cell_size(character, unicode_version):
last_measured_character = character
spans.append((index, index := index + 1, character_width))
total_width += character_width
- elif spans:
- # zero width characters are associated with the previous character
- start, _end, cell_length = spans[-1]
- spans[-1] = (start, index := index + 1, cell_length)
+ else:
+ # Character has zero width
+ if spans:
+ # zero width characters are associated with the previous character
+ start, _end, cell_length = spans[-1]
+ spans[-1] = (start, index := index + 1, cell_length)
+ else:
+ # A zero width character with no prior spans
+ spans.append((index, index := index + 1, 0))
return (spans, total_width)
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