Use core::error::Error trait

Signed-off-by: Denis Varlakov <denis@dfns.co>

Author: survived

Cargo.lock

@@ -13,8 +13,7 @@ rand_core = { version = "0.6", default-features = false }
 sha2 = { version = "0.10", default-features = false }
 serde = { version = "1", default-features = false, features = ["derive"] }
 
-displaydoc = { version = "0.2", default-features = false }
-thiserror = { version = "1", optional = true }
+thiserror = { version = "2", default-features = false }
 
 # We don't use it directy, but we need to enable `serde` feature
 generic-array = { version = "0.14", features = ["serde"] }
@@ -26,5 +25,3 @@ hex = "0.4"
 rand_dev = "0.1"
 rand = "0.8"
 
-[features]
-std = ["thiserror"]

examples/random-generation-protocol/Cargo.toml

@@ -3,13 +3,13 @@
 #![no_std]
 #![forbid(unused_crate_dependencies, missing_docs)]
 
-#[cfg(any(feature = "std", test))]
+#[cfg(test)]
 extern crate std;
 
 extern crate alloc;
 
 mod _unused_deps {
-    // We don't use it directy, but we need to enable `serde` feature
+    // We don't use it directly, but we need to enable `serde` feature
     use generic_array as _;
 }
 
@@ -132,28 +132,23 @@ where
 }
 
 /// Protocol error
-#[derive(Debug, displaydoc::Display)]
-#[cfg_attr(feature = "std", derive(thiserror::Error))]
+#[derive(Debug, thiserror::Error)]
 pub enum Error<RecvErr, SendErr> {
     /// Couldn't send a message in the first round
-    #[displaydoc("send a message at round 1")]
-    Round1Send(#[cfg_attr(feature = "std", source)] SendErr),
+    #[error("send a message at round 1")]
+    Round1Send(#[source] SendErr),
     /// Couldn't receive a message in the first round
-    #[displaydoc("receive messages at round 1")]
-    Round1Receive(
-        #[cfg_attr(feature = "std", source)] CompleteRoundError<RoundInputError, RecvErr>,
-    ),
+    #[error("receive messages at round 1")]
+    Round1Receive(#[source] CompleteRoundError<RoundInputError, RecvErr>),
     /// Couldn't send a message in the second round
-    #[displaydoc("send a message at round 2")]
-    Round2Send(#[cfg_attr(feature = "std", source)] SendErr),
+    #[error("send a message at round 2")]
+    Round2Send(#[source] SendErr),
     /// Couldn't receive a message in the second round
-    #[displaydoc("receive messages at round 2")]
-    Round2Receive(
-        #[cfg_attr(feature = "std", source)] CompleteRoundError<RoundInputError, RecvErr>,
-    ),
+    #[error("receive messages at round 2")]
+    Round2Receive(#[source] CompleteRoundError<RoundInputError, RecvErr>),
 
     /// Some of the parties cheated
-    #[displaydoc("malicious parties: {guilty_parties:?}")]
+    #[error("malicious parties: {guilty_parties:?}")]
     PartiesOpenedRandomnessDoesntMatchCommitment {
         /// List of cheated parties
         guilty_parties: Vec<Blame>,

examples/random-generation-protocol/src/lib.rs

@@ -1,5 +1,5 @@
 ## v0.4.0
-* Improve ergonomics of protocol simulation, which is used for writing tests [#14]
+* BREAKING: Improve ergonomics of protocol simulation, which is used for writing tests [#14]
   * Remove `dev` feature, it's replaced with `sim` and `sim-async`
   * `round_based::simulation` module is renamed into `round_based::sim`
   * `round_based::simulation::Simulation` is renamed and moved to `round_based::sim::async_env::Network`
@@ -12,6 +12,9 @@
   * When `sim-async` feature is enabled, you can use `round_based::sim::async_env::{run, run_with_setup, ...}`,
     but typically you don't want to use them
   * `round_based::simulation::SimulationSync` has been renamed to `round_based::sim::Simulation`
+* Use `core::error::Error` trait which is now always implemented for all errors regardless whether `std` feature
+  is enabled or not [#14]
+  * Update `thiserror` dependency to v2
 
 Migration guidelines:
 * Replace `dev` feature with `sim`

round-based/CHANGELOG.md

@@ -19,8 +19,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 futures-util = { version = "0.3", default-features = false, features = ["sink"] }
 phantom-type = { version = "0.3", default-features = false }
 tracing = { version = "0.1", default-features = false }
-thiserror = { version = "1", optional = true }
-displaydoc = { version = "0.2", default-features = false }
+thiserror = { version = "2", default-features = false }
 
 round-based-derive = { version = "0.2", optional = true, path = "../round-based-derive" }
 
@@ -40,13 +39,13 @@ rand_dev = "0.1"
 anyhow = "1"
 
 [features]
-default = ["std"]
+default = []
 state-machine = []
-sim = ["std", "state-machine"]
+sim = ["state-machine"]
 sim-async = ["sim", "tokio/sync", "tokio-stream", "futures-util/alloc"]
 derive = ["round-based-derive"]
 runtime-tokio = ["tokio"]
-std = ["thiserror"]
+std = []
 
 [[test]]
 name = "derive"

round-based/Cargo.toml

@@ -1,7 +1,5 @@
 use futures_util::{Sink, Stream};
 
-use crate::StdError;
-
 /// Networking abstraction
 ///
 /// Basically, it's pair of channels: [`Stream`] for receiving messages, and [`Sink`] for sending
@@ -12,9 +10,9 @@ pub trait Delivery<M> {
     /// Incoming delivery channel
     type Receive: Stream<Item = Result<Incoming<M>, Self::ReceiveError>> + Unpin;
     /// Error of outgoing delivery channel
-    type SendError: StdError + Send + Sync + 'static;
+    type SendError: core::error::Error + Send + Sync + 'static;
     /// Error of incoming delivery channel
-    type ReceiveError: StdError + Send + Sync + 'static;
+    type ReceiveError: core::error::Error + Send + Sync + 'static;
     /// Returns a pair of incoming and outgoing delivery channels
     fn split(self) -> (Self::Receive, Self::Send);
 }
@@ -23,8 +21,8 @@ impl<M, I, O, IErr, OErr> Delivery<M> for (I, O)
 where
     I: Stream<Item = Result<Incoming<M>, IErr>> + Unpin,
     O: Sink<Outgoing<M>, Error = OErr> + Unpin,
-    IErr: StdError + Send + Sync + 'static,
-    OErr: StdError + Send + Sync + 'static,
+    IErr: core::error::Error + Send + Sync + 'static,
+    OErr: core::error::Error + Send + Sync + 'static,
 {
     type Send = O;
     type Receive = I;

round-based/src/delivery.rs

@@ -93,15 +93,3 @@ pub mod _docs;
 /// See [`ProtocolMessage`] docs for more details
 #[cfg(feature = "derive")]
 pub use round_based_derive::ProtocolMessage;
-
-mod std_error {
-    #[cfg(feature = "std")]
-    pub use std::error::Error as StdError;
-
-    #[cfg(not(feature = "std"))]
-    pub trait StdError: core::fmt::Display + core::fmt::Debug {}
-    #[cfg(not(feature = "std"))]
-    impl<E: core::fmt::Display + core::fmt::Debug> StdError for E {}
-}
-
-use std_error::StdError;

round-based/src/lib.rs

@@ -34,7 +34,6 @@ use phantom_type::PhantomType;
 
 use crate::delivery::Delivery;
 use crate::runtime::{self, AsyncRuntime};
-use crate::StdError;
 
 /// Party of MPC protocol (trait)
 ///
@@ -82,9 +81,9 @@ pub trait Mpc: internal::Sealed {
     type Runtime: AsyncRuntime;
 
     /// Sending message error
-    type SendError: StdError + Send + Sync + 'static;
+    type SendError: core::error::Error + Send + Sync + 'static;
     /// Receiving message error
-    type ReceiveError: StdError + Send + Sync + 'static;
+    type ReceiveError: core::error::Error + Send + Sync + 'static;
 
     /// Converts into [`MpcParty`]
     fn into_party(self) -> MpcParty<Self::ProtocolMessage, Self::Delivery, Self::Runtime>;
@@ -142,8 +141,8 @@ impl<M, D, B> internal::Sealed for MpcParty<M, D, B> {}
 impl<M, D, R> Mpc for MpcParty<M, D, R>
 where
     D: Delivery<M>,
-    D::SendError: StdError + Send + Sync + 'static,
-    D::ReceiveError: StdError + Send + Sync + 'static,
+    D::SendError: core::error::Error + Send + Sync + 'static,
+    D::ReceiveError: core::error::Error + Send + Sync + 'static,
     R: AsyncRuntime,
 {
     type ProtocolMessage = M;