Add tests around DataTable key generation

src/textual/widgets/_data_table.py

@@ -35,15 +35,20 @@ class CellDoesNotExist(Exception):
     pass
 
 
+# TODO: Revisit?
 class Key(NamedTuple):
     value: str | None
 
     def __hash__(self):
-        # TODO: Revisit
         # If a string is supplied, we use the hash of the string.
         # If no string was supplied, we use the default hash to ensure uniqueness amongst instances.
         return hash(self.value) if self.value is not None else super().__hash__(self)
 
+    def __eq__(self, other: object) -> bool:
+        # Strings will match Keys containing the same string value.
+        # Otherwise, you'll need to supply the exact same key object.
+        return hash(self) == hash(other)
+
 
 def default_cell_formatter(obj: object) -> RenderableType | None:
     """Format a cell in to a renderable.

tests/test_data_table.py

@@ -2,6 +2,7 @@ from textual.app import App
 from textual.coordinate import Coordinate
 from textual.message import Message
 from textual.widgets import DataTable
+from textual.widgets._data_table import Key
 
 
 class DataTableApp(App):
@@ -147,3 +148,27 @@ async def test_clear():
         # Clearing the columns too
         table.clear(columns=True)
         assert len(table.columns) == 0
+
+
+def test_key_equals_equivalent_string():
+    text = "Hello"
+    key = Key(text)
+    assert key == text
+    assert hash(key) == hash(text)
+
+
+def test_key_doesnt_match_non_equal_string():
+    key = Key("123")
+    text = "laksjdlaskjd"
+    assert key != text
+    assert hash(key) != hash(text)
+
+
+def test_key_string_lookup():
+    # Indirectly covered by other tests, but let's explicitly show how
+    # we intend for the keys to work for cache lookups.
+    dictionary = {
+        "hello": "world",
+    }
+    assert dictionary["hello"] == "world"
+    assert dictionary[Key("hello")] == "world"