Enforce Optimistic Sync Conditions & CLI Tests (v2) (#3050)

## Description

This PR adds a single, trivial commit (f5d2b27d78) atop #2986 to resolve a tests compile error. The original author (@ethDreamer) is AFK so I'm getting this one merged ☺️ 

Please see #2986 for more information about the other, significant changes in this PR.


Co-authored-by: Mark Mackey <mark@sigmaprime.io>
Co-authored-by: ethDreamer <37123614+ethDreamer@users.noreply.github.com>

consensus/fork_choice/src/fork_choice.rs

@@ -928,6 +928,54 @@ where
             .is_descendant(self.fc_store.finalized_checkpoint().root, block_root)
     }
 
+    /// Returns `Ok(false)` if a block is not viable to be imported optimistically.
+    ///
+    /// ## Notes
+    ///
+    /// Equivalent to the function with the same name in the optimistic sync specs:
+    ///
+    /// https://github.com/ethereum/consensus-specs/blob/dev/sync/optimistic.md#helpers
+    pub fn is_optimistic_candidate_block(
+        &self,
+        current_slot: Slot,
+        block_slot: Slot,
+        block_parent_root: &Hash256,
+        spec: &ChainSpec,
+    ) -> Result<bool, Error<T::Error>> {
+        // If the block is sufficiently old, import it.
+        if block_slot + spec.safe_slots_to_import_optimistically <= current_slot {
+            return Ok(true);
+        }
+
+        // If the justified block has execution enabled, then optimistically import any block.
+        if self
+            .get_justified_block()?
+            .execution_status
+            .is_execution_enabled()
+        {
+            return Ok(true);
+        }
+
+        // If the block has an ancestor with a verified parent, import this block.
+        //
+        // TODO: This condition is not yet merged into the spec. See:
+        //
+        // https://github.com/ethereum/consensus-specs/pull/2841
+        //
+        // ## Note
+        //
+        // If `block_parent_root` is unknown this iter will always return `None`.
+        if self
+            .proto_array
+            .iter_nodes(block_parent_root)
+            .any(|node| node.execution_status.is_valid())
+        {
+            return Ok(true);
+        }
+
+        Ok(false)
+    }
+
     /// Return the current finalized checkpoint.
     pub fn finalized_checkpoint(&self) -> Checkpoint {
         *self.fc_store.finalized_checkpoint()

consensus/proto_array/src/proto_array_fork_choice.rs

@@ -1,5 +1,5 @@
 use crate::error::Error;
-use crate::proto_array::{ProposerBoost, ProtoArray};
+use crate::proto_array::{Iter, ProposerBoost, ProtoArray};
 use crate::ssz_container::SszContainer;
 use serde_derive::{Deserialize, Serialize};
 use ssz::{Decode, Encode};
@@ -40,6 +40,10 @@ pub enum ExecutionStatus {
 }
 
 impl ExecutionStatus {
+    pub fn is_execution_enabled(&self) -> bool {
+        !matches!(self, ExecutionStatus::Irrelevant(_))
+    }
+
     pub fn irrelevant() -> Self {
         ExecutionStatus::Irrelevant(false)
     }
@@ -341,6 +345,11 @@ impl ProtoArrayForkChoice {
         }
     }
 
+    /// See `ProtoArray::iter_nodes`
+    pub fn iter_nodes<'a>(&'a self, block_root: &Hash256) -> Iter<'a> {
+        self.proto_array.iter_nodes(block_root)
+    }
+
     pub fn as_bytes(&self) -> Vec<u8> {
         SszContainer::from(self).as_ssz_bytes()
     }

consensus/types/src/chain_spec.rs

@@ -146,6 +146,7 @@ pub struct ChainSpec {
     pub terminal_total_difficulty: Uint256,
     pub terminal_block_hash: ExecutionBlockHash,
     pub terminal_block_hash_activation_epoch: Epoch,
+    pub safe_slots_to_import_optimistically: u64,
 
     /*
      * Networking
@@ -551,6 +552,7 @@ impl ChainSpec {
                 .expect("addition does not overflow"),
             terminal_block_hash: ExecutionBlockHash::zero(),
             terminal_block_hash_activation_epoch: Epoch::new(u64::MAX),
+            safe_slots_to_import_optimistically: 128u64,
 
             /*
              * Network specific
@@ -748,6 +750,7 @@ impl ChainSpec {
                 .expect("addition does not overflow"),
             terminal_block_hash: ExecutionBlockHash::zero(),
             terminal_block_hash_activation_epoch: Epoch::new(u64::MAX),
+            safe_slots_to_import_optimistically: 128u64,
 
             /*
              * Network specific
@@ -791,6 +794,9 @@ pub struct Config {
     // TODO(merge): remove this default
     #[serde(default = "default_terminal_block_hash_activation_epoch")]
     pub terminal_block_hash_activation_epoch: Epoch,
+    // TODO(merge): remove this default
+    #[serde(default = "default_safe_slots_to_import_optimistically")]
+    pub safe_slots_to_import_optimistically: u64,
 
     #[serde(with = "eth2_serde_utils::quoted_u64")]
     min_genesis_active_validator_count: u64,
@@ -878,6 +884,10 @@ fn default_terminal_block_hash_activation_epoch() -> Epoch {
     Epoch::new(u64::MAX)
 }
 
+fn default_safe_slots_to_import_optimistically() -> u64 {
+    128u64
+}
+
 impl Default for Config {
     fn default() -> Self {
         let chain_spec = MainnetEthSpec::default_spec();
@@ -935,6 +945,7 @@ impl Config {
             terminal_total_difficulty: spec.terminal_total_difficulty,
             terminal_block_hash: spec.terminal_block_hash,
             terminal_block_hash_activation_epoch: spec.terminal_block_hash_activation_epoch,
+            safe_slots_to_import_optimistically: spec.safe_slots_to_import_optimistically,
 
             min_genesis_active_validator_count: spec.min_genesis_active_validator_count,
             min_genesis_time: spec.min_genesis_time,
@@ -985,6 +996,7 @@ impl Config {
             terminal_total_difficulty,
             terminal_block_hash,
             terminal_block_hash_activation_epoch,
+            safe_slots_to_import_optimistically,
             min_genesis_active_validator_count,
             min_genesis_time,
             genesis_fork_version,
@@ -1040,6 +1052,7 @@ impl Config {
             terminal_total_difficulty,
             terminal_block_hash,
             terminal_block_hash_activation_epoch,
+            safe_slots_to_import_optimistically,
             ..chain_spec.clone()
         })
     }
@@ -1227,6 +1240,7 @@ mod yaml_tests {
         #TERMINAL_TOTAL_DIFFICULTY: 115792089237316195423570985008687907853269984665640564039457584007913129638911
         #TERMINAL_BLOCK_HASH: 0x0000000000000000000000000000000000000000000000000000000000000001
         #TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH: 18446744073709551614
+        #SAFE_SLOTS_TO_IMPORT_OPTIMISTICALLY: 2
         MIN_GENESIS_ACTIVE_VALIDATOR_COUNT: 16384
         MIN_GENESIS_TIME: 1606824000
         GENESIS_FORK_VERSION: 0x00000000
@@ -1266,6 +1280,10 @@ mod yaml_tests {
             chain_spec.terminal_block_hash_activation_epoch,
             default_terminal_block_hash_activation_epoch()
         );
+        assert_eq!(
+            chain_spec.safe_slots_to_import_optimistically,
+            default_safe_slots_to_import_optimistically()
+        );
 
         assert_eq!(
             chain_spec.bellatrix_fork_epoch,