Auto-height table repopulate fix (Textualize#4992)

CHANGELOG.md

@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed `RichLog` writing at wrong width when `write` occurs before width is known (e.g. in `compose` or `on_mount`) https://github.com/Textualize/textual/pull/4978
 - Fixed `RichLog.write` incorrectly shrinking width to `RichLog.min_width` when `shrink=True` (now shrinks to fit content area instead) https://github.com/Textualize/textual/pull/4978
 - Fixed flicker when setting `dark` reactive on startup https://github.com/Textualize/textual/pull/4989
+- Fixed `DataTable` cached height issue on re-populating the table when using auto-height rows https://github.com/Textualize/textual/pull/4992
 
 ## [0.79.1] - 2024-08-31
 

src/textual/widgets/_data_table.py

@@ -818,6 +818,7 @@ def _y_offsets(self) -> list[tuple[RowKey, int]]:
             for row in self.ordered_rows:
                 y_offsets += [(row.key, y) for y in range(row.height)]
             self._offset_cache[self._update_count] = y_offsets
+
         return y_offsets
 
     @property
@@ -1397,6 +1398,7 @@ def _update_dimensions(self, new_rows: Iterable[RowKey]) -> None:
         # If there are rows that need to have their height computed, render them correctly
         # so that we can cache this rendering for later.
         if auto_height_rows:
+            self._offset_cache.clear()
             render_cell = self._render_cell  # This method renders & caches.
             should_highlight = self._should_highlight
             cursor_type = self.cursor_type
@@ -1451,6 +1453,9 @@ def _update_dimensions(self, new_rows: Iterable[RowKey]) -> None:
                             ]
                         )
 
+            self._line_cache.clear()
+            self._styles_cache.clear()
+
         data_cells_width = sum(
             column.get_render_width(self) for column in self.columns.values()
         )