check for empty bindings

src/textual/binding.py

@@ -19,6 +19,10 @@ class NoBinding(Exception):
     """A binding was not found."""
 
 
+class InvalidBinding(Exception):
+    """Binding key is in an invalid format."""
+
+
 @dataclass(frozen=True)
 class Binding:
     """The configuration of a key binding."""
@@ -71,10 +75,14 @@ class Bindings:
                 # into a (potential) collection of Binding instances.
                 for key in binding.key.split(","):
                     key = key.strip()
+                    if not key:
+                        raise InvalidBinding(
+                            f"Can not bind empty string in {binding.key!r}"
+                        )
                     if len(key) == 1:
                         key = _character_to_key(key)
                     yield Binding(
-                        key=key.strip(),
+                        key=key,
                         action=binding.action,
                         description=binding.description,
                         show=binding.show,

tests/test_binding.py

@@ -2,7 +2,8 @@ from string import ascii_lowercase
 
 import pytest
 
-from textual.binding import Bindings, Binding, BindingError, NoBinding
+from textual.app import App
+from textual.binding import Bindings, Binding, BindingError, NoBinding, InvalidBinding
 
 BINDING1 = Binding("a,b", action="action1", description="description1")
 BINDING2 = Binding("c", action="action2", description="description2")
@@ -13,45 +14,78 @@ BINDING3 = Binding(" d   , e ", action="action3", description="description3")
 def bindings():
     yield Bindings([BINDING1, BINDING2])
 
+
 @pytest.fixture
 def more_bindings():
     yield Bindings([BINDING1, BINDING2, BINDING3])
 
+
 def test_bindings_get_key(bindings):
-    assert bindings.get_key("b") == Binding("b", action="action1", description="description1")
+    assert bindings.get_key("b") == Binding(
+        "b", action="action1", description="description1"
+    )
     assert bindings.get_key("c") == BINDING2
     with pytest.raises(NoBinding):
         bindings.get_key("control+meta+alt+shift+super+hyper+t")
 
+
 def test_bindings_get_key_spaced_list(more_bindings):
     assert more_bindings.get_key("d").action == more_bindings.get_key("e").action
 
+
 def test_bindings_merge_simple(bindings):
     left = Bindings([BINDING1])
     right = Bindings([BINDING2])
     assert Bindings.merge([left, right]).keys == bindings.keys
 
+
 def test_bindings_merge_overlap():
     left = Bindings([BINDING1])
-    another_binding = Binding("a", action="another_action", description="another_description")
+    another_binding = Binding(
+        "a", action="another_action", description="another_description"
+    )
     assert Bindings.merge([left, Bindings([another_binding])]).keys == {
         "a": another_binding,
         "b": Binding("b", action="action1", description="description1"),
     }
 
+
 def test_bad_binding_tuple():
     with pytest.raises(BindingError):
         _ = Bindings((("a", "action"),))
     with pytest.raises(BindingError):
-        _ = Bindings((("a", "action", "description","too much"),))
+        _ = Bindings((("a", "action", "description", "too much"),))
+
 
 def test_binding_from_tuples():
-    assert Bindings((( BINDING2.key, BINDING2.action, BINDING2.description),)).get_key("c") == BINDING2
+    assert (
+        Bindings(((BINDING2.key, BINDING2.action, BINDING2.description),)).get_key("c")
+        == BINDING2
+    )
+
 
 def test_shown():
-    bindings = Bindings([
-        Binding(
-            key, action=f"action_{key}", description=f"Emits {key}",show=bool(ord(key)%2)
-        ) for key in ascii_lowercase
-    ])
-    assert len(bindings.shown_keys)==(len(ascii_lowercase)/2)
+    bindings = Bindings(
+        [
+            Binding(
+                key,
+                action=f"action_{key}",
+                description=f"Emits {key}",
+                show=bool(ord(key) % 2),
+            )
+            for key in ascii_lowercase
+        ]
+    )
+    assert len(bindings.shown_keys) == (len(ascii_lowercase) / 2)
+
+
+def test_invalid_binding():
+    with pytest.raises(InvalidBinding):
+
+        class BrokenApp(App):
+            BINDINGS = [(",,,", "foo", "Broken")]
+
+    with pytest.raises(InvalidBinding):
+
+        class BrokenApp(App):
+            BINDINGS = [(", ,", "foo", "Broken")]