Raise TypeError on malformed MIDI messages instead of silently dropping them

pedalboard/midi_utils.py

@@ -45,7 +45,7 @@ def normalize_midi_messages(_input) -> List[Tuple[bytes, float]]:
     into a juce::MidiBuffer on the C++ side.
     """
     output = []
-    for message in _input:
+    for index, message in enumerate(_input):
         if hasattr(message, "bytes") and hasattr(message, "time"):
             output.append((bytes(message.bytes()), message.time))
         elif (isinstance(message, tuple) or isinstance(message, list)) and len(message) == 2:
@@ -57,6 +57,13 @@ def normalize_midi_messages(_input) -> List[Tuple[bytes, float]]:
             elif not isinstance(message, bytes):
                 message = bytes(message)
             output.append((message, time))
+        else:
+            raise TypeError(
+                f"Unable to interpret MIDI message at index {index}: {message!r}. "
+                "MIDI messages must either be objects with `bytes` and `time` attributes "
+                "(like mido.Message) or (message, timestamp) tuples, where timestamp is "
+                "the number of seconds from the start of the returned audio buffer."
+            )
 
     # Detect the case in which the provided timestamps
     # are likely delta values rather than absolute values:

tests/test_midi_utils.py

@@ -36,3 +36,29 @@
 )
 def test_mido_normalization(_input, expected: List[Tuple[bytes, float]]):
     assert normalize_midi_messages(_input) == expected
+
+
+@pytest.mark.parametrize(
+    "malformed",
+    [
+        pytest.param((bytes([0x90, 60, 64]),), id="one_tuple_missing_timestamp"),
+        pytest.param((bytes([0x90, 60, 64]), 0.0, 99), id="three_tuple_extra_element"),
+        pytest.param(bytes([0x90, 60, 64]), id="bare_bytes_without_timestamp"),
+        pytest.param(None, id="none"),
+        pytest.param(42, id="bare_int"),
+    ],
+)
+def test_malformed_messages_raise(malformed):
+    """Malformed messages must raise rather than being silently dropped."""
+    messages = [
+        (bytes([0x90, 60, 64]), 0.0),
+        malformed,
+        (bytes([0x80, 60, 64]), 1.0),
+    ]
+    with pytest.raises(TypeError, match="index 1"):
+        normalize_midi_messages(messages)
+
+
+def test_valid_messages_are_unaffected():
+    messages = [(bytes([0x90, 60, 64]), 0.0), (bytes([0x80, 60, 64]), 1.0)]
+    assert normalize_midi_messages(messages) == messages