Restore publish_transaction RPC to Serai

substrate/client/serai/src/lib.rs

@@ -14,18 +14,16 @@ use borsh::BorshDeserialize;
 pub use serai_abi as abi;
 use abi::{
   primitives::{BlockHash, network_id::ExternalNetworkId},
-  Block, Event,
+  Transaction, Block, Event,
 };
 
 use async_lock::RwLock;
 
-/// RPC client functionality for the coins module.
+mod coins;
-pub mod coins;
+pub use coins::Coins;
-use coins::*;
 
-/// RPC client functionality for the validator sets module.
+mod validator_sets;
-pub mod validator_sets;
+pub use validator_sets::ValidatorSets;
-use validator_sets::*;
 
 /// An error from the RPC.
 #[derive(Debug, Error)]
@@ -164,6 +162,16 @@ impl Serai {
     Self::block_internal(self.call("blockchain/block", &format!(r#"{{ "block": {block} }}"#))).await
   }
 
+  /// Publish a transaction onto the Serai blockchain.
+  pub async fn publish_transaction(&self, transaction: &Transaction) -> Result<(), RpcError> {
+    self
+      .call(
+        "blockchain/publish_transaction",
+        &format!(r#"{{ "transaction": {} }}"#, hex::encode(borsh::to_vec(transaction).unwrap())),
+      )
+      .await
+  }
+
   /// Scope this RPC client to the state as of a specific block.
   ///
   /// This will yield an error if the block chosen isn't finalized. This ensures, given an honest

substrate/node/src/rpc/blockchain.rs

@@ -1,4 +1,5 @@
-use std::{sync::Arc, ops::Deref, collections::HashSet};
+use core::{ops::Deref, future::Future};
+use std::{sync::Arc, collections::HashSet};
 
 use rand_core::{RngCore, OsRng};
 
@@ -8,8 +9,9 @@ use sp_consensus::BlockStatus;
 use sp_block_builder::BlockBuilder;
 use sp_api::ProvideRuntimeApi;
 use sc_client_api::BlockBackend;
+use sc_transaction_pool_api::TransactionPool;
 
-use serai_abi::{primitives::prelude::*, SubstrateBlock as Block};
+use serai_abi::{primitives::prelude::*, Transaction, SubstrateBlock as Block};
 
 use serai_runtime::SeraiApi;
 
@@ -27,6 +29,7 @@ pub(crate) fn module<
     + ProvideRuntimeApi<Block, Api: SeraiApi<Block>>,
 >(
   client: Arc<C>,
+  pool: Arc<impl 'static + TransactionPool<Block = Block>>,
 ) -> Result<RpcModule<impl 'static + Send + Sync>, Box<dyn std::error::Error + Send + Sync>> {
   let mut module = RpcModule::new(client);
 
@@ -80,5 +83,36 @@ pub(crate) fn module<
     )
   })?;
 
+  module.register_async_method("blockchain/publish_transaction", move |params, client, _ext| {
+    let pool = pool.clone();
+    async move {
+      #[derive(sp_core::serde::Deserialize)]
+      #[serde(crate = "sp_core::serde")]
+      struct TransactionRequest {
+        transaction: String,
+      };
+      let Ok(transaction) = params.parse::<TransactionRequest>() else {
+        return Err(Error::InvalidRequest(r#"missing `string` "transaction" field"#));
+      };
+      let Ok(transaction) = hex::decode(transaction.transaction) else {
+        Err(Error::InvalidRequest(r#"transaction was not hex-encoded"#))?
+      };
+      let Ok(transaction) =
+        <Transaction as borsh::BorshDeserialize>::deserialize_reader(&mut transaction.as_slice())
+      else {
+        Err(Error::InvalidRequest(r#"transaction could not be deserialized"#))?
+      };
+      pool
+        .submit_one(
+          client.info().best_hash,
+          sc_transaction_pool_api::TransactionSource::External,
+          transaction,
+        )
+        .await
+        .map_err(|e| Error::InvalidTransaction(format!("{e}")))?;
+      Ok(())
+    }
+  })?;
+
   Ok(module)
 }

substrate/node/src/rpc/mod.rs

@@ -36,14 +36,14 @@ pub fn create_full<
     + HeaderBackend<Block>
     + HeaderMetadata<Block, Error = BlockchainError>
     + BlockBackend<Block>,
-  P: 'static + TransactionPool,
+  P: 'static + TransactionPool<Block = Block>,
 >(
   deps: FullDeps<C, P>,
 ) -> Result<RpcModule<()>, Box<dyn std::error::Error + Send + Sync>> {
   let FullDeps { id, client, pool, authority_discovery } = deps;
 
   let mut root = RpcModule::new(());
-  root.merge(blockchain::module(client.clone())?)?;
+  root.merge(blockchain::module(client.clone(), pool)?)?;
   root.merge(validator_sets::module(client.clone()))?;
   if let Some(authority_discovery) = authority_discovery {
     root.merge(p2p_validators::module(id, client, authority_discovery)?)?;

substrate/node/src/rpc/utils.rs

@@ -7,6 +7,7 @@ pub(super) enum Error {
   Internal(&'static str),
   InvalidRequest(&'static str),
   InvalidStateReference,
+  InvalidTransaction(String),
 }
 
 impl From<Error> for jsonrpsee::types::error::ErrorObjectOwned {
@@ -19,10 +20,15 @@ impl From<Error> for jsonrpsee::types::error::ErrorObjectOwned {
         jsonrpsee::types::error::ErrorObjectOwned::owned(-2, str, Option::<()>::None)
       }
       Error::InvalidStateReference => jsonrpsee::types::error::ErrorObjectOwned::owned(
-        -4,
+        -3,
         "the block used as the reference was not locally held",
         Option::<()>::None,
       ),
+      Error::InvalidTransaction(str) => jsonrpsee::types::error::ErrorObjectOwned::owned(
+        -4,
+        format!("transaction was not accepted to the mempool: {str}"),
+        Option::<()>::None,
+      ),
     }
   }
 }