Use RPC call to get account nonce (#476)

* remove code related to getting nonce from storage and use RPC call instead

* cargo fmt

* move nonce fetching into Rpc, since it's just an RPC call

* clippy

subxt/src/client.rs

@@ -37,7 +37,6 @@ use crate::{
     },
     storage::StorageClient,
     transaction::TransactionProgress,
-    AccountData,
     Call,
     Config,
     Metadata,
@@ -170,23 +169,6 @@ impl<T: Config> Client<T> {
         StorageClient::new(&self.rpc, &self.metadata, self.iter_page_size)
     }
 
-    /// Fetch the current nonce for the given account id.
-    pub async fn fetch_nonce<A: AccountData>(
-        &self,
-        account: &T::AccountId,
-    ) -> Result<T::Index, BasicError>
-    where
-        <A as AccountData>::AccountId: From<<T as Config>::AccountId>,
-        <A as AccountData>::Index: Into<<T as Config>::Index>,
-    {
-        let account_storage_entry = A::storage_entry(account.clone().into());
-        let account_data = self
-            .storage()
-            .fetch_or_default(&account_storage_entry, None)
-            .await?;
-        Ok(A::nonce(&account_data).into())
-    }
-
     /// Convert the client to a runtime api wrapper for custom runtime access.
     ///
     /// The `subxt` proc macro will provide methods to submit extrinsics and read storage specific
@@ -197,17 +179,16 @@ impl<T: Config> Client<T> {
 }
 
 /// A constructed call ready to be signed and submitted.
-pub struct SubmittableExtrinsic<'client, T: Config, X, A, C, E: Decode, Evs: Decode> {
+pub struct SubmittableExtrinsic<'client, T: Config, X, C, E: Decode, Evs: Decode> {
     client: &'client Client<T>,
     call: C,
-    marker: std::marker::PhantomData<(X, A, E, Evs)>,
+    marker: std::marker::PhantomData<(X, E, Evs)>,
 }
 
-impl<'client, T, X, A, C, E, Evs> SubmittableExtrinsic<'client, T, X, A, C, E, Evs>
+impl<'client, T, X, C, E, Evs> SubmittableExtrinsic<'client, T, X, C, E, Evs>
 where
     T: Config,
     X: SignedExtra<T>,
-    A: AccountData,
     C: Call + Send + Sync,
     E: Decode + HasModuleError,
     Evs: Decode,
@@ -232,8 +213,6 @@ where
     where
         <<X as SignedExtra<T>>::Extra as SignedExtension>::AdditionalSigned:
             Send + Sync + 'static,
-        <A as AccountData>::AccountId: From<<T as Config>::AccountId>,
-        <A as AccountData>::Index: Into<<T as Config>::Index>,
     {
         // Sign the call data to create our extrinsic.
         let extrinsic = self.create_signed(signer, Default::default()).await?;
@@ -262,8 +241,6 @@ where
     where
         <<X as SignedExtra<T>>::Extra as SignedExtension>::AdditionalSigned:
             Send + Sync + 'static,
-        <A as AccountData>::AccountId: From<<T as Config>::AccountId>,
-        <A as AccountData>::Index: Into<<T as Config>::Index>,
     {
         let extrinsic = self.create_signed(signer, Default::default()).await?;
         self.client.rpc().submit_extrinsic(extrinsic).await
@@ -278,13 +255,14 @@ where
     where
         <<X as SignedExtra<T>>::Extra as SignedExtension>::AdditionalSigned:
             Send + Sync + 'static,
-        <A as AccountData>::AccountId: From<<T as Config>::AccountId>,
-        <A as AccountData>::Index: Into<<T as Config>::Index>,
     {
         let account_nonce = if let Some(nonce) = signer.nonce() {
             nonce
         } else {
-            self.client.fetch_nonce::<A>(signer.account_id()).await?
+            self.client
+                .rpc()
+                .system_account_next_index(signer.account_id())
+                .await?
         };
         let call = self
             .client

subxt/src/config.rs

@@ -14,7 +14,6 @@
 // You should have received a copy of the GNU General Public License
 // along with subxt.  If not, see <http://www.gnu.org/licenses/>.
 
-use crate::StorageEntry;
 use codec::{
     Codec,
     Encode,
@@ -38,7 +37,13 @@ use sp_runtime::traits::{
 pub trait Config: 'static {
     /// Account index (aka nonce) type. This stores the number of previous
     /// transactions associated with a sender account.
-    type Index: Parameter + Member + Default + AtLeast32Bit + Copy + scale_info::TypeInfo;
+    type Index: Parameter
+        + Member
+        + serde::de::DeserializeOwned
+        + Default
+        + AtLeast32Bit
+        + Copy
+        + scale_info::TypeInfo;
 
     /// The block number type used by the runtime.
     type BlockNumber: Parameter
@@ -65,7 +70,7 @@ pub trait Config: 'static {
     type Hashing: Hash<Output = Self::Hash>;
 
     /// The user account identifier type for the runtime.
-    type AccountId: Parameter + Member;
+    type AccountId: Parameter + Member + serde::Serialize;
 
     /// The address type. This instead of `<frame_system::Trait::Lookup as StaticLookup>::Source`.
     type Address: Codec + Clone + PartialEq;
@@ -103,22 +108,3 @@ impl Config for DefaultConfig {
     type Signature = sp_runtime::MultiSignature;
     type Extrinsic = sp_runtime::OpaqueExtrinsic;
 }
-
-/// Trait to fetch data about an account.
-pub trait AccountData {
-    /// The runtime storage entry from which the account data can be fetched.
-    /// Usually generated by the `subxt` macro.
-    type StorageEntry: StorageEntry;
-
-    /// The type of the account id to fetch the account data for.
-    type AccountId;
-
-    /// The type of the account nonce returned from storage.
-    type Index;
-
-    /// Create a new storage entry key from the account id.
-    fn storage_entry(account_id: Self::AccountId) -> Self::StorageEntry;
-
-    /// Get the nonce from the storage entry value.
-    fn nonce(result: &<Self::StorageEntry as StorageEntry>::Value) -> Self::Index;
-}

subxt/src/lib.rs

@@ -73,7 +73,6 @@ pub use crate::{
         SubmittableExtrinsic,
     },
     config::{
-        AccountData,
         Config,
         DefaultConfig,
     },

subxt/src/rpc.rs

@@ -324,6 +324,17 @@ impl<T: Config> Rpc<T> {
         Ok(self.client.request("system_version", rpc_params![]).await?)
     }
 
+    /// Fetch the current nonce for the given account ID.
+    pub async fn system_account_next_index(
+        &self,
+        account: &T::AccountId,
+    ) -> Result<T::Index, BasicError> {
+        Ok(self
+            .client
+            .request("system_accountNextIndex", rpc_params![account])
+            .await?)
+    }
+
     /// Get a header
     pub async fn header(
         &self,