fixed some method return error types

src/audio.rs

@@ -45,6 +45,7 @@ impl MediaPlayerAudioEx for MediaPlayer {
             }
         }
     }
+
     fn get_audio_track_description(&self) -> Option<Vec<TrackDescription>> {
         unsafe {
             let p0 = sys::libvlc_audio_get_track_description(self.ptr);

src/core.rs

@@ -53,7 +53,7 @@ impl Instance {
     /// Create and initialize a libvlc instance with specified args.
     /// Note: args.len() has to be less or equal to i32::MAX
     /// Note: libvlc discourages using arguments as these are not guaranteed to be stable between different versions of libvlc
-    pub fn with_args(args: Option<Vec<String>>) -> Option<Instance> {
+    pub fn with_args(args: Option<Vec<String>>) -> Result<Instance, InternalError> {
         let args_c_ptr: Vec<*const c_char>;
         let args_c: Vec<CString>;
         if let Some(argv) = args {
@@ -74,15 +74,15 @@ impl Instance {
             };
 
             if p.is_null() {
-                return None;
+                Err(InternalError)
+            } else {
+                Ok(Instance { ptr: p })
             }
-
-            Some(Instance { ptr: p })
         }
     }
 
     /// Create and initialize a libvlc instance.
-    pub fn new() -> Option<Instance> {
+    pub fn new() -> Result<Instance, InternalError> {
         Instance::with_args(None)
     }
 
@@ -125,25 +125,25 @@ impl Instance {
     }
 
     /// Returns a list of audio filters that are available.
-    pub fn audio_filter_list_get(&self) -> Option<ModuleDescriptionList> {
+    pub fn audio_filter_list_get(&self) -> Result<ModuleDescriptionList, InternalError> {
         unsafe {
             let p = sys::libvlc_audio_filter_list_get(self.ptr);
             if p.is_null() {
-                None
+                Err(InternalError)
             } else {
-                Some(ModuleDescriptionList { ptr: p })
+                Ok(ModuleDescriptionList { ptr: p })
             }
         }
     }
 
     /// Returns a list of video filters that are available.
-    pub fn video_filter_list_get(&self) -> Option<ModuleDescriptionList> {
+    pub fn video_filter_list_get(&self) -> Result<ModuleDescriptionList, InternalError> {
         unsafe {
             let p = sys::libvlc_video_filter_list_get(self.ptr);
             if p.is_null() {
-                None
+                Err(InternalError)
             } else {
-                Some(ModuleDescriptionList { ptr: p })
+                Ok(ModuleDescriptionList { ptr: p })
             }
         }
     }

src/media_library.rs

@@ -3,6 +3,7 @@
 // Licensed under the MIT license, see the LICENSE file.
 
 use crate::{Instance, InternalError, MediaList};
+use std::fmt;
 use vlc_sys as sys;
 
 pub struct MediaLibrary {
@@ -11,13 +12,13 @@ pub struct MediaLibrary {
 
 impl MediaLibrary {
     /// Create an new Media Library object.
-    pub fn new(instance: &Instance) -> Option<MediaLibrary> {
+    pub fn new(instance: &Instance) -> Result<MediaLibrary, InternalError> {
         unsafe {
             let p = sys::libvlc_media_library_new(instance.ptr);
             if p.is_null() {
-                None
+                Err(InternalError)
             } else {
-                Some(MediaLibrary { ptr: p })
+                Ok(MediaLibrary { ptr: p })
             }
         }
     }

src/media_list.rs

@@ -11,13 +11,13 @@ pub struct MediaList {
 
 impl MediaList {
     /// Create an empty media list.
-    pub fn new(instance: &Instance) -> Option<MediaList> {
+    pub fn new(instance: &Instance) -> Result<MediaList, InternalError> {
         unsafe {
             let p = sys::libvlc_media_list_new(instance.ptr);
             if p.is_null() {
-                None
+                Err(InternalError)
             } else {
-                Some(MediaList { ptr: p })
+                Ok(MediaList { ptr: p })
             }
         }
     }
@@ -45,6 +45,7 @@ impl MediaList {
 
     /// Add media instance to media list.
     /// The MediaList::lock should be held upon entering this function.
+    // TODO: use specific error type since documentation says "-1 if the media list is read-only"
     pub fn add_media(&self, md: &Media) -> Result<(), InternalError> {
         unsafe {
             if sys::libvlc_media_list_add_media(self.ptr, md.ptr) == 0 {