feat: refactor signing in order to more easily be able to dryrun (#547)

* feat: refactor signing in order to more easily be able to dryrun

Co-authored-by: Sander Bosma <sanderbosma@gmail.com>
Co-authored-by: Daniel Savu <savudani04@yahoo.ro>

* chore: move dry_run to rpc file

* fix: failing dryrun test

* fix: run cargo fmt

* chore(dryrun): Replace complex SubmittableExtrinsic type with bytes array

* cargo fmt

* feat: add dry_run method to signed submittable extrinsic

* fmt

Co-authored-by: Sander Bosma <sanderbosma@gmail.com>

subxt/src/rpc.rs

@@ -146,9 +146,12 @@ use sp_core::{
     Bytes,
     U256,
 };
-use sp_runtime::generic::{
-    Block,
-    SignedBlock,
+use sp_runtime::{
+    generic::{
+        Block,
+        SignedBlock,
+    },
+    ApplyExtrinsicResult,
 };
 
 /// A number type that can be serialized both as a number or a string that encodes a number in a
@@ -643,6 +646,21 @@ impl<T: Config> Rpc<T> {
         let params = rpc_params![public_key, key_type];
         Ok(self.client.request("author_hasKey", params).await?)
     }
+
+    /// Submits the extrinsic to the dry_run RPC, to test if it would succeed.
+    ///
+    /// Returns `Ok` with an [`ApplyExtrinsicResult`], which is the result of applying of an extrinsic.
+    pub async fn dry_run(
+        &self,
+        encoded_signed: &[u8],
+        at: Option<T::Hash>,
+    ) -> Result<ApplyExtrinsicResult, BasicError> {
+        let params = rpc_params![format!("0x{}", hex::encode(encoded_signed)), at];
+        let result_bytes: Bytes = self.client.request("system_dryRun", params).await?;
+        let data: ApplyExtrinsicResult =
+            codec::Decode::decode(&mut result_bytes.0.as_slice())?;
+        Ok(data)
+    }
 }
 
 /// Build WS RPC client from URL