fix: use pending block tag for actual pending block (#4966)

crates/rpc/rpc/src/eth/api/mod.rs

@@ -263,8 +263,9 @@ where
 
         let mut cfg = CfgEnv::default();
         let mut block_env = BlockEnv::default();
-        self.provider().fill_block_env_with_header(&mut block_env, origin.header())?;
-        self.provider().fill_cfg_env_with_header(&mut cfg, origin.header())?;
+        // Note: for the PENDING block we assume it is past the known merge block and thus this will
+        // not fail when looking up the total difficulty value for the blockenv.
+        self.provider().fill_env_with_header(&mut cfg, &mut block_env, origin.header())?;
 
         Ok(PendingBlockEnv { cfg, block_env, origin })
     }

crates/rpc/rpc/src/eth/api/pending_block.rs

@@ -4,8 +4,8 @@ use crate::eth::error::{EthApiError, EthResult};
 use core::fmt::Debug;
 use reth_primitives::{
     constants::{eip4844::MAX_DATA_GAS_PER_BLOCK, BEACON_NONCE},
-    proofs, Block, ChainSpec, Header, IntoRecoveredTransaction, Receipt, Receipts, SealedBlock,
-    SealedHeader, B256, EMPTY_OMMER_ROOT, U256,
+    proofs, Block, BlockId, BlockNumberOrTag, ChainSpec, Header, IntoRecoveredTransaction, Receipt,
+    Receipts, SealedBlock, SealedHeader, B256, EMPTY_OMMER_ROOT, U256,
 };
 use reth_provider::{BundleStateWithReceipts, ChainSpecProvider, StateProviderFactory};
 use reth_revm::{
@@ -305,7 +305,18 @@ impl PendingBlockEnvOrigin {
         }
     }
 
-    /// Returns the hash of the pending block should be built on
+    /// Returns the [BlockId] that represents the state of the block.
+    ///
+    /// If this is the actual pending block, the state is the "Pending" tag, otherwise we can safely
+    /// identify the block by its hash.
+    pub(crate) fn state_block_id(&self) -> BlockId {
+        match self {
+            PendingBlockEnvOrigin::ActualPending(_) => BlockNumberOrTag::Pending.into(),
+            PendingBlockEnvOrigin::DerivedFromLatest(header) => BlockId::Hash(header.hash.into()),
+        }
+    }
+
+    /// Returns the hash of the block the pending block should be built on.
     fn build_target_hash(&self) -> B256 {
         match self {
             PendingBlockEnvOrigin::ActualPending(block) => block.parent_hash,

crates/rpc/rpc/src/eth/api/transactions.rs

@@ -69,8 +69,10 @@ pub trait EthTransactions: Send + Sync {
 
     /// Returns the revm evm env for the requested [BlockId]
     ///
-    /// If the [BlockId] this will return the [BlockId::Hash] of the block the env was configured
+    /// If the [BlockId] this will return the [BlockId] of the block the env was configured
     /// for.
+    /// If the [BlockId] is pending, this will return the "Pending" tag, otherwise this returns the
+    /// hash of the exact block.
     async fn evm_env_at(&self, at: BlockId) -> EthResult<(CfgEnv, BlockEnv, BlockId)>;
 
     /// Returns the revm evm env for the raw block header
@@ -279,7 +281,7 @@ where
     async fn evm_env_at(&self, at: BlockId) -> EthResult<(CfgEnv, BlockEnv, BlockId)> {
         if at.is_pending() {
             let PendingBlockEnv { cfg, block_env, origin } = self.pending_block_env_and_cfg()?;
-            Ok((cfg, block_env, origin.header().hash.into()))
+            Ok((cfg, block_env, origin.state_block_id()))
         } else {
             //  Use cached values if there is no pending block
             let block_hash = self

crates/storage/provider/src/providers/mod.rs

@@ -521,14 +521,20 @@ where
         state
     }
 
-    /// Storage provider for pending state.
+    /// Returns the state provider for pending state.
+    ///
+    /// If there's no pending block available then the latest state provider is returned:
+    /// [Self::latest]
     fn pending(&self) -> RethResult<StateProviderBox<'_>> {
         trace!(target: "providers::blockchain", "Getting provider for pending state");
 
         if let Some(block) = self.tree.pending_block_num_hash() {
-            let pending = self.tree.pending_state_provider(block.hash)?;
+            if let Ok(pending) = self.tree.pending_state_provider(block.hash) {
                 return self.pending_with_provider(pending)
             }
+        }
+
+        // fallback to latest state if the pending block is not available
         self.latest()
     }
 

crates/storage/provider/src/traits/state.rs

@@ -107,7 +107,8 @@ pub trait StateProviderFactory: BlockIdReader + Send + Sync {
 
     /// Returns a [StateProvider] indexed by the given [BlockId].
     ///
-    /// Note: if a number or hash is provided this will only look at historical(canonical) state.
+    /// Note: if a number or hash is provided this will __only__ look at historical(canonical)
+    /// state.
     fn state_by_block_id(&self, block_id: BlockId) -> RethResult<StateProviderBox<'_>> {
         match block_id {
             BlockId::Number(block_number) => self.state_by_block_number_or_tag(block_number),