feat(filler): Add prepare_call method (#2011)

* feat(filler): Add a new method to allow users customize transaction requests for eth_call

* feat(filler): Add a new method to FillProvider to prepare txRequest which might be useful

* feat(filler): Implement default method for wallet to set address

crates/provider/src/fillers/mod.rs

@@ -200,6 +200,16 @@ pub trait TxFiller<N: Network = Ethereum>: Clone + Send + Sync + std::fmt::Debug
             self.fill(fillable, tx).await
         }
     }
+
+    /// Prepares transaction request with necessary fillers required for eth_call operations
+    fn prepare_call(
+        &self,
+        tx: &mut N::TransactionRequest,
+    ) -> impl_future!(<Output = TransportResult<()>>) {
+        let _ = tx;
+        // This is a no-op by default
+        futures::future::ready(Ok(()))
+    }
 }
 
 /// A [`Provider`] that applies one or more [`TxFiller`]s.
@@ -268,6 +278,15 @@ where
     pub async fn fill(&self, tx: N::TransactionRequest) -> TransportResult<SendableTx<N>> {
         self.fill_inner(SendableTx::Builder(tx)).await
     }
+
+    /// Prepares a transaction request for eth_call operations using the configured fillers
+    pub async fn prepare_call(
+        &self,
+        mut tx: N::TransactionRequest,
+    ) -> TransportResult<N::TransactionRequest> {
+        self.filler.prepare_call(&mut tx).await?;
+        Ok(tx)
+    }
 }
 
 #[cfg_attr(target_arch = "wasm32", async_trait(?Send))]

crates/provider/src/fillers/wallet.rs

@@ -101,6 +101,13 @@ where
 
         Ok(SendableTx::Envelope(envelope))
     }
+
+    async fn prepare_call(&self, tx: &mut N::TransactionRequest) -> TransportResult<()> {
+        if tx.from().is_none() {
+            tx.set_from(self.wallet.default_signer_address());
+        }
+        Ok(())
+    }
 }
 
 #[cfg(feature = "reqwest")]