Add explicit error message when swapping the samplerate and num_channels arguments on AudioFile.

pedalboard/io/WriteableAudioFile.h

@@ -234,7 +234,7 @@ class WriteableAudioFile
     pybind11::gil_scoped_release release;
 
     if (!isInteger(writeSampleRate)) {
-      throw std::domain_error(
+      throw py::type_error(
           "Opening an audio file for writing requires an integer sample rate.");
     }
 
@@ -244,8 +244,22 @@ class WriteableAudioFile
     }
 
     if (numChannels == 0) {
-      throw py::type_error("Opening an audio file for writing requires a "
-                           "non-zero num_channels.");
+      throw std::domain_error("Opening an audio file for writing requires a "
+                              "non-zero num_channels.");
+    }
+
+    // Tiny quality-of-life improvement to try to detect if people have swapped
+    // the num_channels and samplerate arguments:
+    if ((numChannels == 48000 || numChannels == 44100 || numChannels == 22050 ||
+         numChannels == 11025) &&
+        writeSampleRate < 8000) {
+      throw std::domain_error(
+          "Arguments of num_channels=" + std::to_string(numChannels) +
+          " and samplerate=" + std::to_string(writeSampleRate) +
+          " were provided when opening a file for writing. These arguments "
+          "appear to be flipped, and may cause an invalid audio file to be "
+          "written. Try reversing the order of the samplerate "
+          "and num_channels arguments.");
     }
 
     registerPedalboardAudioFormats(formatManager, true);

tests/test_io.py

@@ -719,7 +719,7 @@ def test_write_twice_overwrites(
 @pytest.mark.parametrize("samplerate", [1234.5, 23.0000000001])
 def test_fractional_sample_rates(tmp_path: pathlib.Path, extension: str, samplerate):
     filename = str(tmp_path / f"test{extension}")
-    with pytest.raises(ValueError):
+    with pytest.raises(TypeError):
         pedalboard.io.WriteableAudioFile(filename, samplerate=samplerate, num_channels=1)
 
 
@@ -755,6 +755,17 @@ def test_sample_rate_is_int_by_default(samplerate: int):
         assert f.samplerate == samplerate
 
 
+@pytest.mark.parametrize("extension", [".flac"])
+@pytest.mark.parametrize("samplerate", [22050, 44100, 48000])
+def test_swapped_parameter_exception(tmp_path: pathlib.Path, extension: str, samplerate):
+    filename = str(tmp_path / f"test{extension}")
+    with pytest.raises(ValueError) as e:
+        pedalboard.io.WriteableAudioFile(filename, samplerate=1, num_channels=samplerate)
+    assert "reversing" in str(
+        e
+    ), "Expected exception to include details about reversing parameters."
+
+
 @pytest.mark.parametrize("dtype", [np.uint8, np.uint16, np.uint32, np.uint64])
 def test_fail_to_write_unsigned(tmp_path: pathlib.Path, dtype):
     filename = str(tmp_path / "test.wav")