Fork schedule api (#2525)

## Issue Addressed

Resolves #2524

## Proposed Changes

- Return all known forks in the `/config/fork_schedule`, previously returned only the head of the chain's fork.
- Deleted the `StateId::head` method because it was only previously used in this endpoint.


Co-authored-by: realbigsean <seananderson33@gmail.com>

beacon_node/http_api/src/lib.rs

@@ -40,7 +40,7 @@ use tokio::sync::mpsc::UnboundedSender;
 use tokio_stream::{wrappers::BroadcastStream, StreamExt};
 use types::{
     Attestation, AttesterSlashing, BeaconStateError, CommitteeCache, ConfigAndPreset, Epoch,
-    EthSpec, ProposerSlashing, RelativeEpoch, SignedAggregateAndProof, SignedBeaconBlock,
+    EthSpec, ForkName, ProposerSlashing, RelativeEpoch, SignedAggregateAndProof, SignedBeaconBlock,
     SignedContributionAndProof, SignedVoluntaryExit, Slot, SyncCommitteeMessage,
     SyncContributionData,
 };
@@ -1366,7 +1366,7 @@ pub fn serve<T: BeaconChainTypes>(
         );
 
     /*
-     * config/fork_schedule
+     * config
      */
 
     let config_path = eth1_v1.and(warp::path("config"));
@@ -1378,9 +1378,11 @@ pub fn serve<T: BeaconChainTypes>(
         .and(chain_filter.clone())
         .and_then(|chain: Arc<BeaconChain<T>>| {
             blocking_json_task(move || {
-                StateId::head()
-                    .fork(&chain)
-                    .map(|fork| api_types::GenericResponse::from(vec![fork]))
+                let forks = ForkName::list_all()
+                    .into_iter()
+                    .filter_map(|fork_name| chain.spec.fork_for_name(fork_name))
+                    .collect::<Vec<_>>();
+                Ok(api_types::GenericResponse::from(forks))
             })
         });
 

beacon_node/http_api/src/state_id.rs

@@ -8,10 +8,6 @@ use types::{BeaconState, EthSpec, Fork, Hash256, Slot};
 pub struct StateId(CoreStateId);
 
 impl StateId {
-    pub fn head() -> Self {
-        Self(CoreStateId::Head)
-    }
-
     pub fn slot(slot: Slot) -> Self {
         Self(CoreStateId::Slot(slot))
     }

beacon_node/http_api/tests/tests.rs

@@ -1190,7 +1190,10 @@ impl ApiTester {
     pub async fn test_get_config_fork_schedule(self) -> Self {
         let result = self.client.get_config_fork_schedule().await.unwrap().data;
 
-        let expected = vec![self.chain.head_info().unwrap().fork];
+        let expected: Vec<Fork> = ForkName::list_all()
+            .into_iter()
+            .filter_map(|fork| self.chain.spec.fork_for_name(fork))
+            .collect();
 
         assert_eq!(result, expected);
 

consensus/types/src/chain_spec.rs

@@ -237,6 +237,19 @@ impl ChainSpec {
         }
     }
 
+    /// Returns a full `Fork` struct for a given `ForkName` or `None` if the fork does not yet have
+    /// an activation epoch.
+    pub fn fork_for_name(&self, fork_name: ForkName) -> Option<Fork> {
+        let previous_fork_name = fork_name.previous_fork().unwrap_or(ForkName::Base);
+        let epoch = self.fork_epoch(fork_name)?;
+
+        Some(Fork {
+            previous_version: self.fork_version_for_name(previous_fork_name),
+            current_version: self.fork_version_for_name(fork_name),
+            epoch,
+        })
+    }
+
     /// Get the domain number, unmodified by the fork.
     ///
     /// Spec v0.12.1