Measuring string cells correctly

src/textual/render.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from rich.cells import cell_len
 from rich.console import Console, RenderableType
 from rich.protocol import rich_cast
 
@@ -22,6 +23,9 @@ def measure(
     Returns:
         Width in cells
     """
+    if isinstance(renderable, str):
+        return cell_len(renderable)
+
     width = default
     renderable = rich_cast(renderable)
     get_console_width = getattr(renderable, "__rich_measure__", None)

src/textual/widgets/_data_table.py

@@ -524,8 +524,6 @@ class DataTable(ScrollView, Generic[CellType], can_focus=True):
             update_width: Whether to resize the column width to accommodate
                 for the new cell content.
         """
-        value = Text.from_markup(value) if isinstance(value, str) else value
-
         self.data[row_key][column_key] = value
         self._update_count += 1
 
@@ -752,6 +750,7 @@ class DataTable(ScrollView, Generic[CellType], can_focus=True):
             label_width = measure(console, column.label, 1)
             content_width = column.content_width
             cell_value = self.data[row_key][column_key]
+
             new_content_width = measure(console, cell_value, 1)
 
             if new_content_width < content_width:
@@ -866,15 +865,13 @@ class DataTable(ScrollView, Generic[CellType], can_focus=True):
                 of its current location in the DataTable (it could have moved after being added
                 due to sorting or insertion/deletion of other columns).
         """
-        text_label = Text.from_markup(label) if isinstance(label, str) else label
-
         column_key = ColumnKey(key)
         column_index = len(self.columns)
-        content_width = measure(self.app.console, text_label, 1)
+        content_width = measure(self.app.console, label, 1)
         if width is None:
             column = Column(
                 column_key,
-                text_label,
+                label,
                 content_width,
                 content_width=content_width,
                 auto_width=True,
@@ -882,7 +879,7 @@ class DataTable(ScrollView, Generic[CellType], can_focus=True):
         else:
             column = Column(
                 column_key,
-                text_label,
+                label,
                 width,
                 content_width=content_width,
             )

tests/test_data_table.py

@@ -178,7 +178,6 @@ async def test_add_columns():
         assert len(table.columns) == 3
 
 
-# TODO: Ensure we can use the key to retrieve the column.
 async def test_add_columns_user_defined_keys():
     app = DataTableApp()
     async with app.run_test():
@@ -223,7 +222,7 @@ async def test_column_labels() -> None:
         table = app.query_one(DataTable)
         table.add_columns("1", "2", "3")
         actual_labels = [col.label for col in table.columns.values()]
-        expected_labels = [Text("1"), Text("2"), Text("3")]
+        expected_labels = ["1", "2", "3"]
         assert actual_labels == expected_labels
 
 
@@ -294,13 +293,17 @@ async def test_get_value_at_exception():
             table.get_value_at(Coordinate(9999, 0))
 
 
-# async def test_update_cell_cell_exists():
-#     app = DataTableApp()
-#     async with app.run_test():
-#         table = app.query_one(DataTable)
-#         table.add_column("A", key="A")
-#         table.add_row("1", key="1")
-#         assert table.get_cell_value()
+async def test_update_cell_cell_exists():
+    app = DataTableApp()
+    async with app.run_test():
+        table = app.query_one(DataTable)
+        table.add_column("A", key="A")
+        table.add_row("1", key="1")
+        table.update_cell("1", "A", "NEW_VALUE")
+        assert table.get_cell_value("1", "A") == "NEW_VALUE"
+
+
+# TODO: Test update coordinate
 
 
 def test_key_equals_equivalent_string():