fatality based errors (#4448)

* seed commit for fatality based errors

* fatality

* first draft of fatality

* cleanup

* differnt approach

* simplify

* first working version for enums, with documentation

* add split

* fix simple split test case

* extend README.md

* update fatality impl

* make tests passed

* apply fatality to first subsystem

* fatality fixes

* use fatality in a subsystem

* fix subsystemg

* fixup proc macro

* fix/test: log::*! do not execute when log handler is missing

* fix spelling

* rename Runtime2 to something sane

* allow nested split with `forward` annotations

* add free license

* enable and fixup all tests

* use external fatality

Makes this more reviewable.

* bump fatality dep

Avoid duplicate expander compilations.

* migrate availability distribution

* more fatality usage

* chore: bump fatality to 0.0.6

* fixup remaining subsystems

* chore: fmt

* make cargo spellcheck happy

* remove single instance of `#[fatal(false)]`

* last quality sweep

* fixup

polkadot/node/subsystem-util/Cargo.toml

@@ -13,6 +13,7 @@ parity-scale-codec = { version = "3.0.0", default-features = false, features = [
 pin-project = "1.0.9"
 rand = "0.8.5"
 thiserror = "1.0.30"
+fatality = "0.0.6"
 tracing = "0.1.31"
 derive_more = "0.99.17"
 lru = "0.7.2"
@@ -38,4 +39,3 @@ log = "0.4.13"
 polkadot-node-subsystem-test-helpers = { path = "../subsystem-test-helpers" }
 lazy_static = "1.4.0"
 polkadot-primitives-test-helpers = { path = "../../primitives/test-helpers" }
-

polkadot/node/subsystem-util/src/runtime/error.rs

@@ -18,34 +18,18 @@
 //! Error handling related code and Error/Result definitions.
 
 use futures::channel::oneshot;
-use thiserror::Error;
 
 use polkadot_node_subsystem::errors::RuntimeApiError;
 use polkadot_primitives::v1::SessionIndex;
 
-pub type Result<T> = std::result::Result<T, Error>;
-
-/// Errors for `Runtime` cache.
-#[derive(Debug, Error, derive_more::From)]
-#[error(transparent)]
+#[allow(missing_docs)]
+#[fatality::fatality(splitable)]
 pub enum Error {
-	/// All fatal errors.
-	Fatal(Fatal),
-	/// All nonfatal/potentially recoverable errors.
-	NonFatal(NonFatal),
-}
-
-/// Fatal runtime errors.
-#[derive(Debug, Error)]
-pub enum Fatal {
 	/// Runtime API subsystem is down, which means we're shutting down.
+	#[fatal]
 	#[error("Runtime request got canceled")]
 	RuntimeRequestCanceled(oneshot::Canceled),
-}
 
-/// Errors for fetching of runtime information.
-#[derive(Debug, Error)]
-pub enum NonFatal {
 	/// Some request to the runtime failed.
 	/// For example if we prune a block we're requesting info about.
 	#[error("Runtime API error {0}")]
@@ -56,13 +40,15 @@ pub enum NonFatal {
 	NoSuchSession(SessionIndex),
 }
 
+pub type Result<T> = std::result::Result<T, Error>;
+
 /// Receive a response from a runtime request and convert errors.
 pub(crate) async fn recv_runtime<V>(
 	r: oneshot::Receiver<std::result::Result<V, RuntimeApiError>>,
 ) -> Result<V> {
 	let result = r
 		.await
-		.map_err(Fatal::RuntimeRequestCanceled)?
-		.map_err(NonFatal::RuntimeRequest)?;
+		.map_err(FatalError::RuntimeRequestCanceled)?
+		.map_err(JfyiError::RuntimeRequest)?;
 	Ok(result)
 }

polkadot/node/subsystem-util/src/runtime/mod.rs

@@ -44,7 +44,7 @@ use crate::{
 mod error;
 
 use error::{recv_runtime, Result};
-pub use error::{Error, Fatal, NonFatal};
+pub use error::{Error, FatalError, JfyiError};
 
 /// Configuration for construction a `RuntimeInfo`.
 pub struct Config {
@@ -169,7 +169,7 @@ impl RuntimeInfo {
 			let session_info =
 				recv_runtime(request_session_info(parent, session_index, sender).await)
 					.await?
-					.ok_or(NonFatal::NoSuchSession(session_index))?;
+					.ok_or(JfyiError::NoSuchSession(session_index))?;
 			let validator_info = self.get_validator_info(&session_info).await?;
 
 			let full_info = ExtendedSessionInfo { session_info, validator_info };