Improve handling of the `DefaultFormatError`

src/alsa/mod.rs

@@ -313,8 +313,7 @@ impl Device {
                     return Err(DefaultFormatError::StreamTypeNotSupported);
                 }
                 Err(SupportedFormatsError::BackendSpecific { err }) => {
-                    unimplemented!();
-                    //return Err(err.into());
+                    return Err(err.into());
                 }
                 Ok(fmts) => fmts.collect(),
             }

src/coreaudio/mod.rs

@@ -224,18 +224,25 @@ impl Device {
         scope: AudioObjectPropertyScope,
     ) -> Result<Format, DefaultFormatError>
     {
-        fn default_format_error_from_os_status(status: OSStatus) -> Option<DefaultFormatError> {
+        fn default_format_error_from_os_status(status: OSStatus) -> Result<(), DefaultFormatError> {
             let err = match coreaudio::Error::from_os_status(status) {
                 Err(err) => err,
-                Ok(_) => return None,
+                Ok(_) => return Ok(()),
             };
             match err {
-                coreaudio::Error::RenderCallbackBufferFormatDoesNotMatchAudioUnitStreamFormat |
-                coreaudio::Error::NoKnownSubtype |
                 coreaudio::Error::AudioUnit(coreaudio::error::AudioUnitError::FormatNotSupported) |
                 coreaudio::Error::AudioCodec(_) |
-                coreaudio::Error::AudioFormat(_) => Some(DefaultFormatError::StreamTypeNotSupported),
-                _ => Some(DefaultFormatError::DeviceNotAvailable),
+                coreaudio::Error::AudioFormat(_) => {
+                    Err(DefaultFormatError::StreamTypeNotSupported)
+                }
+                coreaudio::Error::AudioUnit(coreaudio::error::AudioUnitError::NoConnection) => {
+                    Err(DefaultFormatError::DeviceNotAvailable)
+                }
+                err => {
+                    let description = format!("{}", std::error::Error::description(&err));
+                    let err = BackendSpecificError { description };
+                    Err(err.into())
+                }
             }
         }
 
@@ -256,12 +263,7 @@ impl Device {
                 &data_size as *const _ as *mut _,
                 &asbd as *const _ as *mut _,
             );
-
-            if status != kAudioHardwareNoError as i32 {
-                let err = default_format_error_from_os_status(status)
-                    .expect("no known error for OSStatus");
-                return Err(err);
-            }
+            default_format_error_from_os_status(status)?;
 
             let sample_format = {
                 let audio_format = coreaudio::audio_unit::AudioFormat::from_format_and_flag(

src/lib.rs

@@ -347,6 +347,12 @@ pub enum DefaultFormatError {
     /// Returned if e.g. the default input format was requested on an output-only audio device.
     #[fail(display = "The requested stream type is not supported by the device.")]
     StreamTypeNotSupported,
+    /// See the `BackendSpecificError` docs for more information about this error variant.
+    #[fail(display = "{}", err)]
+    BackendSpecific {
+        #[fail(cause)]
+        err: BackendSpecificError,
+    }
 }
 
 /// Error that can happen when creating a `Stream`.
@@ -765,6 +771,12 @@ impl From<BackendSpecificError> for SupportedFormatsError {
     }
 }
 
+impl From<BackendSpecificError> for DefaultFormatError {
+    fn from(err: BackendSpecificError) -> Self {
+        DefaultFormatError::BackendSpecific { err }
+    }
+}
+
 // If a backend does not provide an API for retrieving supported formats, we query it with a bunch
 // of commonly used rates. This is always the case for wasapi and is sometimes the case for alsa.
 //

src/wasapi/device.rs

@@ -522,9 +522,15 @@ impl Device {
         com::com_initialized();
 
         let lock = match self.ensure_future_audio_client() {
-            Err(ref e) if e.raw_os_error() == Some(AUDCLNT_E_DEVICE_INVALIDATED) =>
-                return Err(DefaultFormatError::DeviceNotAvailable),
-            e => e.unwrap(),
+            Ok(lock) => lock,
+            Err(ref e) if e.raw_os_error() == Some(AUDCLNT_E_DEVICE_INVALIDATED) => {
+                return Err(DefaultFormatError::DeviceNotAvailable)
+            }
+            Err(e) => {
+                let description = format!("{}", e);
+                let err = BackendSpecificError { description };
+                return Err(err.into());
+            }
         };
         let client = lock.unwrap().0;
 
@@ -534,7 +540,11 @@ impl Device {
                 Err(ref e) if e.raw_os_error() == Some(AUDCLNT_E_DEVICE_INVALIDATED) => {
                     return Err(DefaultFormatError::DeviceNotAvailable);
                 },
-                Err(e) => panic!("{:?}", e),
+                Err(e) => {
+                    let description = format!("{}", e);
+                    let err = BackendSpecificError { description };
+                    return Err(err.into());
+                },
                 Ok(()) => (),
             };