Change TextArea to delete empty line on ctrl+k

Following the expected behaviour for ctrl+k from Emacs (and so by extension
a text area on macOS -- see notes.app, or textedit.app, for example), this
adds an alternative action to TextArea that will delete to end of line or,
if the line is empty, will delete the line.

Also, to further enhance compatibility with expected ctrl+k behaviour, if
the cursor is on the end of the line and ctrl+k is pressed a delete-right is
performed.

Fixes Textualize#4277.

CHANGELOG.md

@@ -46,6 +46,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - BREAKING: `AppFocus` and `AppBlur` are now posted when the terminal window gains or loses focus, if the terminal supports this https://github.com/Textualize/textual/pull/4265
   - When the terminal window loses focus, the currently-focused widget will also lose focus.
   - When the terminal window regains focus, the previously-focused widget will regain focus.
+- TextArea binding for <key>ctrl</key>+<key>k</key> will now delete the line if the line is empty https://github.com/Textualize/textual/issues/4277
 
 ## [0.52.1] - 2024-02-20
 

src/textual/widgets/_text_area.py

@@ -219,7 +219,12 @@ class TextArea(ScrollView):
         Binding(
             "ctrl+u", "delete_to_start_of_line", "delete to line start", show=False
         ),
-        Binding("ctrl+k", "delete_to_end_of_line", "delete to line end", show=False),
+        Binding(
+            "ctrl+k",
+            "delete_to_end_of_line_or_delete_line",
+            "delete to line end",
+            show=False,
+        ),
         Binding("ctrl+z", "undo", "Undo", show=False),
         Binding("ctrl+y", "redo", "Redo", show=False),
     ]
@@ -2112,6 +2117,26 @@ def action_delete_to_end_of_line(self) -> None:
         to_location = self.get_cursor_line_end_location()
         self._delete_via_keyboard(from_location, to_location)
 
+    async def action_delete_to_end_of_line_or_delete_line(self) -> None:
+        """Deletes from the cursor location to the end of the line, or deletes the line.
+
+        The line will be deleted if the line is empty.
+        """
+        # Assume we're just going to delete to the end of the line.
+        action = "delete_to_end_of_line"
+        if self.get_cursor_line_start_location() == self.get_cursor_line_end_location():
+            # The line is empty, so we'll simply remove the line itself.
+            action = "delete_line"
+        elif (
+            self.selection.start
+            == self.selection.end
+            == self.get_cursor_line_end_location()
+        ):
+            # We're at the end of the line, so the kill delete operation
+            # should join the next line to this.
+            action = "delete_right"
+        await self.run_action(action)
+
     def action_delete_word_left(self) -> None:
         """Deletes the word to the left of the cursor and updates the cursor location."""
         if self.cursor_at_start_of_text: