fix: eth_getBlockByNumber should return Latest if Pending is None (#194)

* fix: eth_getBlockByNumber should return Latest if Pending is None

* style: improve readibility of fn block_by_number

* style: removing extra whitespaces in fn test_get_pending_block

Author: Parizval

crates/flashblocks-rpc/src/rpc.rs

@@ -175,7 +175,13 @@ where
         if number.is_pending() {
             self.metrics.get_block_by_number.increment(1);
             let pending_blocks = self.flashblocks_state.get_pending_blocks();
-            Ok(pending_blocks.get_block(full))
+            if pending_blocks.as_ref().is_some() {
+                return Ok(pending_blocks.get_block(full));
+            }
+            // No pending state available — treat `pending` as `latest`
+            EthBlocks::rpc_block(&self.eth_api, BlockNumberOrTag::Latest.into(), full)
+                .await
+                .map_err(Into::into)
         } else {
             EthBlocks::rpc_block(&self.eth_api, number.into(), full).await.map_err(Into::into)
         }

crates/flashblocks-rpc/src/tests/rpc.rs

@@ -384,9 +384,13 @@ mod tests {
         assert_eq!(latest_block.number(), 0);
 
         // Querying pending block when it does not exist yet
-        let pending_block =
-            provider.get_block_by_number(alloy_eips::BlockNumberOrTag::Pending).await?;
-        assert_eq!(pending_block.is_none(), true);
+        let pending_block = provider
+            .get_block_by_number(alloy_eips::BlockNumberOrTag::Pending)
+            .await?
+            .expect("latest block expected");
+
+        assert_eq!(pending_block.number(), latest_block.number());
+        assert_eq!(pending_block.hash(), latest_block.hash());
 
         let base_payload = create_first_payload();
         node.send_payload(base_payload).await?;