use thiserror to remove error.rs boilerplate

rust/protocol/Cargo.toml

@@ -30,6 +30,7 @@ log = "0.4"
 num_enum = "0.5.1"
 uuid = "0.8"
 displaydoc = "0.2"
+thiserror = "1.0.30"
 
 [features]
 armv8 = ["aes/armv8", "aes-gcm-siv/armv8"]

rust/protocol/src/error.rs

@@ -6,23 +6,26 @@
 use crate::curve::KeyType;
 
 use displaydoc::Display;
+use thiserror::Error;
 
-use std::error::Error;
 use std::panic::UnwindSafe;
 
 pub type Result<T> = std::result::Result<T, SignalProtocolError>;
 
-#[derive(Debug, Display)]
+#[derive(Debug, Display, Error)]
 pub enum SignalProtocolError {
     /// invalid argument: {0}
     InvalidArgument(String),
     /// invalid state for call to {0} to succeed: {1}
     InvalidState(&'static str, String),
 
+    // TODO: avoid duplicating error information in the Display impl and the #[from] or #[source]
+    // attribute if/when we switch to using an error reporting mechanism supporting stack traces:
+    // see https://github.com/yaahc/blog.rust-lang.org/blob/master/posts/inside-rust/2021-05-15-What-the-error-handling-project-group-is-working-towards.md#duplicate-information-issue
     /// failed to decode protobuf: {0}
-    ProtobufDecodingError(prost::DecodeError),
+    ProtobufDecodingError(#[from] prost::DecodeError),
     /// failed to encode protobuf: {0}
-    ProtobufEncodingError(prost::EncodeError),
+    ProtobufEncodingError(#[from] prost::EncodeError),
     /// protobuf encoding was invalid
     InvalidProtobufEncoding,
 
@@ -93,7 +96,7 @@ pub enum SignalProtocolError {
     /// error in method call '{0}': {1}
     ApplicationCallbackError(
         &'static str,
-        Box<dyn std::error::Error + Send + Sync + UnwindSafe + 'static>,
+        #[source] Box<dyn std::error::Error + Send + Sync + UnwindSafe + 'static>,
     ),
 
     /// invalid sealed sender message {0}
@@ -103,26 +106,3 @@ pub enum SignalProtocolError {
     /// self send of a sealed sender message
     SealedSenderSelfSend,
 }
-
-impl Error for SignalProtocolError {
-    fn source(&self) -> Option<&(dyn Error + 'static)> {
-        match self {
-            SignalProtocolError::ProtobufEncodingError(e) => Some(e),
-            SignalProtocolError::ProtobufDecodingError(e) => Some(e),
-            SignalProtocolError::ApplicationCallbackError(_, e) => Some(e.as_ref()),
-            _ => None,
-        }
-    }
-}
-
-impl From<prost::DecodeError> for SignalProtocolError {
-    fn from(value: prost::DecodeError) -> SignalProtocolError {
-        SignalProtocolError::ProtobufDecodingError(value)
-    }
-}
-
-impl From<prost::EncodeError> for SignalProtocolError {
-    fn from(value: prost::EncodeError) -> SignalProtocolError {
-        SignalProtocolError::ProtobufEncodingError(value)
-    }
-}