feat: erase implementation-specific provider error (#484)

Changes the `Other` variant of `ProviderError` to use a trait object instead of a generic parameter. This makes the `ProviderError` type much easier to work with, as errors from different `Provider` types are now compatible, and any type that wraps `ProviderError` will have one fewer generic parameter to deal with. At the same time, it's still possible, though harder, to access the erased error type by downcasting, which requires the caller to know the concrete type at compile time, as showcased in the new example. This is a breaking change, but it shouldn't affect downstream applications which already erase the whole `ProviderError` type with something like `anyhow`.
xJonathanLEI · Oct 29, 2023 · c166e93 · c166e93
1 parent 33e200d
commit c166e93
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diff --git a/README.md b/README.md
@@ -98,6 +98,8 @@ Examples can be found in the [examples folder](./examples):
 
 9. [Parsing a JSON-RPC request on the server side](./examples/parse_jsonrpc_request.rs)
 
+10. [Inspecting a erased provider-specific error type](./examples/downcast_provider_error.rs)
+
 ## License
 
 Licensed under either of

diff --git a/examples/downcast_provider_error.rs b/examples/downcast_provider_error.rs
@@ -0,0 +1,26 @@
+use starknet_providers::{
+    jsonrpc::{HttpTransport, HttpTransportError, JsonRpcClient, JsonRpcClientError},
+    Provider, ProviderError,
+};
+use url::Url;
+
+#[tokio::main]
+async fn main() {
+    let rpc_client =
+        JsonRpcClient::new(HttpTransport::new(Url::parse("https://fake.url/").unwrap()));
+
+    let error = match rpc_client.block_number().await.unwrap_err() {
+        ProviderError::Other(inner) => inner,
+        _ => panic!("unexpected error variant"),
+    };
+
+    // The implementation-specific error type is erased to make the `ProviderError` type easier to
+    // work with. Here, we showcase how to recover the inner type.
+    let impl_specific_error: &JsonRpcClientError<HttpTransportError> =
+        match error.as_any().downcast_ref() {
+            Some(inner) => inner,
+            None => panic!("unexpected downcast failure"),
+        };
+
+    dbg!(impl_specific_error);
+}
diff --git a/starknet-accounts/src/account/declaration.rs b/starknet-accounts/src/account/declaration.rs
@@ -99,9 +99,7 @@ impl<'a, A> Declaration<'a, A>
 where
     A: ConnectedAccount + Sync,
 {
-    pub async fn estimate_fee(
-        &self,
-    ) -> Result<FeeEstimate, AccountError<A::SignError, <A::Provider as Provider>::Error>> {
+    pub async fn estimate_fee(&self) -> Result<FeeEstimate, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -119,8 +117,7 @@ where
         &self,
         skip_validate: bool,
         skip_fee_charge: bool,
-    ) -> Result<SimulatedTransaction, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    ) -> Result<SimulatedTransaction, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -135,21 +132,11 @@ where
             .await
     }
 
-    pub async fn send(
-        &self,
-    ) -> Result<
-        DeclareTransactionResult,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    pub async fn send(&self) -> Result<DeclareTransactionResult, AccountError<A::SignError>> {
         self.prepare().await?.send().await
     }
 
-    async fn prepare(
-        &self,
-    ) -> Result<
-        PreparedDeclaration<'a, A>,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    async fn prepare(&self) -> Result<PreparedDeclaration<'a, A>, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -183,7 +170,7 @@ where
     async fn estimate_fee_with_nonce(
         &self,
         nonce: FieldElement,
-    ) -> Result<FeeEstimate, AccountError<A::SignError, <A::Provider as Provider>::Error>> {
+    ) -> Result<FeeEstimate, AccountError<A::SignError>> {
         let prepared = PreparedDeclaration {
             account: self.account,
             inner: RawDeclaration {
@@ -210,8 +197,7 @@ where
         nonce: FieldElement,
         skip_validate: bool,
         skip_fee_charge: bool,
-    ) -> Result<SimulatedTransaction, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    ) -> Result<SimulatedTransaction, AccountError<A::SignError>> {
         let prepared = PreparedDeclaration {
             account: self.account,
             inner: RawDeclaration {
@@ -298,9 +284,7 @@ impl<'a, A> LegacyDeclaration<'a, A>
 where
     A: ConnectedAccount + Sync,
 {
-    pub async fn estimate_fee(
-        &self,
-    ) -> Result<FeeEstimate, AccountError<A::SignError, <A::Provider as Provider>::Error>> {
+    pub async fn estimate_fee(&self) -> Result<FeeEstimate, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -318,8 +302,7 @@ where
         &self,
         skip_validate: bool,
         skip_fee_charge: bool,
-    ) -> Result<SimulatedTransaction, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    ) -> Result<SimulatedTransaction, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -334,21 +317,13 @@ where
             .await
     }
 
-    pub async fn send(
-        &self,
-    ) -> Result<
-        DeclareTransactionResult,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    pub async fn send(&self) -> Result<DeclareTransactionResult, AccountError<A::SignError>> {
         self.prepare().await?.send().await
     }
 
     async fn prepare(
         &self,
-    ) -> Result<
-        PreparedLegacyDeclaration<'a, A>,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    ) -> Result<PreparedLegacyDeclaration<'a, A>, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -381,7 +356,7 @@ where
     async fn estimate_fee_with_nonce(
         &self,
         nonce: FieldElement,
-    ) -> Result<FeeEstimate, AccountError<A::SignError, <A::Provider as Provider>::Error>> {
+    ) -> Result<FeeEstimate, AccountError<A::SignError>> {
         let prepared = PreparedLegacyDeclaration {
             account: self.account,
             inner: RawLegacyDeclaration {
@@ -407,8 +382,7 @@ where
         nonce: FieldElement,
         skip_validate: bool,
         skip_fee_charge: bool,
-    ) -> Result<SimulatedTransaction, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    ) -> Result<SimulatedTransaction, AccountError<A::SignError>> {
         let prepared = PreparedLegacyDeclaration {
             account: self.account,
             inner: RawLegacyDeclaration {
@@ -505,12 +479,7 @@ impl<'a, A> PreparedDeclaration<'a, A>
 where
     A: ConnectedAccount,
 {
-    pub async fn send(
-        &self,
-    ) -> Result<
-        DeclareTransactionResult,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    pub async fn send(&self) -> Result<DeclareTransactionResult, AccountError<A::SignError>> {
         let tx_request = self.get_declare_request(false).await?;
         self.account
             .provider()
@@ -522,10 +491,7 @@ where
     pub async fn get_declare_request(
         &self,
         query_only: bool,
-    ) -> Result<
-        BroadcastedDeclareTransactionV2,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    ) -> Result<BroadcastedDeclareTransactionV2, AccountError<A::SignError>> {
         let signature = self
             .account
             .sign_declaration(&self.inner, query_only)
@@ -563,12 +529,7 @@ impl<'a, A> PreparedLegacyDeclaration<'a, A>
 where
     A: ConnectedAccount,
 {
-    pub async fn send(
-        &self,
-    ) -> Result<
-        DeclareTransactionResult,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    pub async fn send(&self) -> Result<DeclareTransactionResult, AccountError<A::SignError>> {
         let tx_request = self.get_declare_request(false).await?;
         self.account
             .provider()
@@ -580,10 +541,7 @@ where
     pub async fn get_declare_request(
         &self,
         query_only: bool,
-    ) -> Result<
-        BroadcastedDeclareTransactionV1,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    ) -> Result<BroadcastedDeclareTransactionV1, AccountError<A::SignError>> {
         let signature = self
             .account
             .sign_legacy_declaration(&self.inner, query_only)

diff --git a/starknet-accounts/src/account/execution.rs b/starknet-accounts/src/account/execution.rs
@@ -82,9 +82,7 @@ impl<'a, A> Execution<'a, A>
 where
     A: ConnectedAccount + Sync,
 {
-    pub async fn estimate_fee(
-        &self,
-    ) -> Result<FeeEstimate, AccountError<A::SignError, <A::Provider as Provider>::Error>> {
+    pub async fn estimate_fee(&self) -> Result<FeeEstimate, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -102,8 +100,7 @@ where
         &self,
         skip_validate: bool,
         skip_fee_charge: bool,
-    ) -> Result<SimulatedTransaction, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    ) -> Result<SimulatedTransaction, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -118,19 +115,11 @@ where
             .await
     }
 
-    pub async fn send(
-        &self,
-    ) -> Result<InvokeTransactionResult, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    pub async fn send(&self) -> Result<InvokeTransactionResult, AccountError<A::SignError>> {
         self.prepare().await?.send().await
     }
 
-    async fn prepare(
-        &self,
-    ) -> Result<
-        PreparedExecution<'a, A>,
-        AccountError<A::SignError, <A::Provider as Provider>::Error>,
-    > {
+    async fn prepare(&self) -> Result<PreparedExecution<'a, A>, AccountError<A::SignError>> {
         // Resolves nonce
         let nonce = match self.nonce {
             Some(value) => value,
@@ -163,7 +152,7 @@ where
     async fn estimate_fee_with_nonce(
         &self,
         nonce: FieldElement,
-    ) -> Result<FeeEstimate, AccountError<A::SignError, <A::Provider as Provider>::Error>> {
+    ) -> Result<FeeEstimate, AccountError<A::SignError>> {
         let prepared = PreparedExecution {
             account: self.account,
             inner: RawExecution {
@@ -192,8 +181,7 @@ where
         nonce: FieldElement,
         skip_validate: bool,
         skip_fee_charge: bool,
-    ) -> Result<SimulatedTransaction, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    ) -> Result<SimulatedTransaction, AccountError<A::SignError>> {
         let prepared = PreparedExecution {
             account: self.account,
             inner: RawExecution {
@@ -276,10 +264,7 @@ impl<'a, A> PreparedExecution<'a, A>
 where
     A: ConnectedAccount,
 {
-    pub async fn send(
-        &self,
-    ) -> Result<InvokeTransactionResult, AccountError<A::SignError, <A::Provider as Provider>::Error>>
-    {
+    pub async fn send(&self) -> Result<InvokeTransactionResult, AccountError<A::SignError>> {
         let tx_request = self
             .get_invoke_request(false)
             .await

diff --git a/starknet-accounts/src/account/mod.rs b/starknet-accounts/src/account/mod.rs
@@ -80,9 +80,7 @@ pub trait ConnectedAccount: Account {
         BlockId::Tag(BlockTag::Latest)
     }
 
-    async fn get_nonce(
-        &self,
-    ) -> Result<FieldElement, ProviderError<<Self::Provider as Provider>::Error>> {
+    async fn get_nonce(&self) -> Result<FieldElement, ProviderError> {
         self.provider()
             .get_nonce(self.block_id(), self.address())
             .await
@@ -170,11 +168,11 @@ pub struct PreparedLegacyDeclaration<'a, A> {
 }
 
 #[derive(Debug, thiserror::Error)]
-pub enum AccountError<S, P> {
+pub enum AccountError<S> {
     #[error(transparent)]
     Signing(S),
     #[error(transparent)]
-    Provider(ProviderError<P>),
+    Provider(ProviderError),
     #[error(transparent)]
     ClassHashCalculation(ComputeClassHashError),
     #[error(transparent)]