Minor refactoring

src/textual/_xterm_parser.py

@@ -221,9 +221,7 @@ def reissue_sequence_as_keys(reissue_sequence: str) -> None:
                     for event in sequence_to_key_events(character):
                         on_token(event)
 
-    def _sequence_to_key_events(
-        self, sequence: str, _unicode_name=unicodedata.name
-    ) -> Iterable[events.Key]:
+    def _sequence_to_key_events(self, sequence: str) -> Iterable[events.Key]:
         """Map a sequence of code points on to a sequence of keys.
 
         Args:
@@ -237,12 +235,5 @@ def _sequence_to_key_events(
             for key in keys:
                 yield events.Key(key.value, sequence if len(sequence) == 1 else None)
         elif len(sequence) == 1:
-            try:
-                if not sequence.isalnum():
-                    name = _character_to_key(sequence)
-                else:
-                    name = sequence
-                name = KEY_NAME_REPLACEMENTS.get(name, name)
-                yield events.Key(name, sequence)
-            except:
-                yield events.Key(sequence, sequence)
+            name = _character_to_key(sequence)
+            yield events.Key(name, sequence)

src/textual/keys.py

@@ -304,10 +304,20 @@ def _get_key_display(key: str) -> str:
 def _character_to_key(character: str) -> str:
     """Convert a single character to a key value.
 
+    If `character` has no key value, return it unchanged.
+
     This transformation can be undone by the function `_get_unicode_name_from_key`.
     """
     if not character.isalnum():
-        key = unicodedata.name(character).lower().replace("-", "_").replace(" ", "_")
+        try:
+            key = unicodedata.name(character)
+        except (TypeError, ValueError):
+            # ValueError: `character` has no name. Control characters, for
+            # example, have no name: https://stackoverflow.com/questions/70074668
+            # TypeError: `character` is not a single character.
+            key = character
+        else:
+            key = key.lower().replace("-", "_").replace(" ", "_")
     else:
         key = character
     key = KEY_NAME_REPLACEMENTS.get(key, key)

tests/test_keys.py

@@ -17,6 +17,7 @@
         ("?", "question_mark"),
         ("£", "pound_sign"),
         (",", "comma"),
+        (r"\t", r"\t"),
     ],
 )
 def test_character_to_key(character: str, key: str) -> None: