Remove duplicated top-level EncodableSnapshot fields

consensus/integration/epoch_test.go

@@ -205,6 +205,8 @@ func withNextEpoch(
 
 	// convert to encodable representation for simple modification
 	encodableSnapshot := snapshot.Encodable()
+	rootResult, rootSeal, err := snapshot.SealedResult()
+	require.NoError(t, err)
 
 	rootProtocolState := encodableSnapshot.SealingSegment.LatestProtocolStateEntry()
 	epochProtocolState := rootProtocolState.EpochEntry
@@ -236,7 +238,7 @@ func withNextEpoch(
 		ActiveIdentities: flow.DynamicIdentityEntryListFromIdentities(nextEpochIdentities),
 	}
 	// Re-construct epoch protocol state with modified events (constructs ActiveIdentity fields)
-	epochProtocolState, err := flow.NewRichProtocolStateEntry(
+	epochProtocolState, err = flow.NewRichProtocolStateEntry(
 		epochProtocolState.ProtocolStateEntry,
 		epochProtocolState.PreviousEpochSetup, epochProtocolState.PreviousEpochCommit,
 		currEpochSetup, currEpochCommit,
@@ -258,16 +260,18 @@ func withNextEpoch(
 	}
 
 	// Since we modified the root protocol state, we need to update the root block's ProtocolStateID field.
+	// rootBlock is a pointer, so mutations apply to Snapshot
 	rootBlock := encodableSnapshot.SealingSegment.Blocks[0]
 	rootBlockPayload := rootBlock.Payload
 	rootBlockPayload.ProtocolStateID = rootKVStore.ID()
 	rootBlock.SetPayload(*rootBlockPayload)
 	// Since we changed the root block, we need to update the QC, root result, and root seal.
-	encodableSnapshot.LatestResult.BlockID = rootBlock.ID()
-	encodableSnapshot.LatestSeal.ResultID = encodableSnapshot.LatestResult.ID()
-	encodableSnapshot.LatestSeal.BlockID = rootBlock.ID()
+	// rootResult and rootSeal are pointers, so mutations apply to Snapshot
+	rootResult.BlockID = rootBlock.ID()
+	rootSeal.ResultID = rootResult.ID()
+	rootSeal.BlockID = rootBlock.ID()
 	encodableSnapshot.SealingSegment.LatestSeals = map[flow.Identifier]flow.Identifier{
-		rootBlock.ID(): encodableSnapshot.LatestSeal.ID(),
+		rootBlock.ID(): rootSeal.ID(),
 	}
 	encodableSnapshot.QuorumCertificate = createQC(rootBlock)
 

state/protocol/badger/snapshot_test.go

@@ -40,7 +40,7 @@ func TestUnknownReferenceBlock(t *testing.T) {
 
 	util.RunWithFullProtocolState(t, rootSnapshot, func(db *badger.DB, state *bprotocol.ParticipantState) {
 		// build some finalized non-root blocks (heights 101-110)
-		head := unittest.BlockWithParentFixture(rootSnapshot.Encodable().Head)
+		head := unittest.BlockWithParentFixture(rootSnapshot.Encodable().Head())
 		head.SetPayload(unittest.PayloadFixture(unittest.WithProtocolStateID(rootProtocolStateID)))
 		buildFinalizedBlock(t, state, head)
 
@@ -808,7 +808,7 @@ func TestSealingSegment_FailureCases(t *testing.T) {
 	// Here, we want to specifically test correct handling of the edge case, where a block exists in storage
 	// that has _lower height_ than the node's local root block. Such blocks are typically contained in the
 	// bootstrapping data, such that all entities referenced in the local root block can be resolved.
-	// Is is possible to retrieve blocks that are lower than the local root block from storage, directly
+	// It is possible to retrieve blocks that are lower than the local root block from storage, directly
 	// via their ID. Despite these blocks existing in storage, SealingSegment construction should be
 	// because the known history is potentially insufficient when going below the root block.
 	t.Run("sealing segment from block below local state root", func(t *testing.T) {

state/protocol/badger/state_test.go

@@ -180,7 +180,7 @@ func TestBootstrap_EpochHeightBoundaries(t *testing.T) {
 	t.Parallel()
 	// start with a regular post-spork root snapshot
 	rootSnapshot := unittest.RootSnapshotFixture(unittest.CompleteIdentitySet())
-	epoch1FirstHeight := rootSnapshot.Encodable().Head.Height
+	epoch1FirstHeight := rootSnapshot.Encodable().Head().Height
 
 	// For the spork root snapshot, only the first height of the root epoch should be indexed.
 	// [x]
@@ -609,7 +609,7 @@ func TestBootstrap_SealMismatch(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(unittest.CompleteIdentitySet())
 		// convert to encodable to easily modify snapshot
 		encodable := rootSnapshot.Encodable()
-		encodable.LatestSeal.BlockID = unittest.IdentifierFixture()
+		encodable.LatestSeal().BlockID = unittest.IdentifierFixture()
 
 		bootstrap(t, rootSnapshot, func(state *bprotocol.State, err error) {
 			assert.Error(t, err)
@@ -620,7 +620,7 @@ func TestBootstrap_SealMismatch(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(unittest.CompleteIdentitySet())
 		// convert to encodable to easily modify snapshot
 		encodable := rootSnapshot.Encodable()
-		encodable.LatestResult.BlockID = unittest.IdentifierFixture()
+		encodable.LatestSealedResult().BlockID = unittest.IdentifierFixture()
 
 		bootstrap(t, rootSnapshot, func(state *bprotocol.State, err error) {
 			assert.Error(t, err)
@@ -631,7 +631,7 @@ func TestBootstrap_SealMismatch(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(unittest.CompleteIdentitySet())
 		// convert to encodable to easily modify snapshot
 		encodable := rootSnapshot.Encodable()
-		encodable.LatestSeal.ResultID = unittest.IdentifierFixture()
+		encodable.LatestSeal().ResultID = unittest.IdentifierFixture()
 
 		bootstrap(t, rootSnapshot, func(state *bprotocol.State, err error) {
 			assert.Error(t, err)

state/protocol/badger/validity.go

@@ -20,14 +20,14 @@ func IsValidRootSnapshot(snap protocol.Snapshot, verifyResultID bool) error {
 	if err != nil {
 		return fmt.Errorf("could not get sealing segment: %w", err)
 	}
-	result, seal, err := snap.SealedResult()
+	err = segment.Validate()
 	if err != nil {
-		return fmt.Errorf("could not latest sealed result: %w", err)
+		return fmt.Errorf("invalid root sealing segment: %w", err)
 	}
 
-	err = segment.Validate()
+	result, seal, err := snap.SealedResult()
 	if err != nil {
-		return fmt.Errorf("invalid root sealing segment: %w", err)
+		return fmt.Errorf("could not latest sealed result: %w", err)
 	}
 
 	highest := segment.Highest() // reference block of the snapshot

state/protocol/badger/validity_test.go

@@ -24,14 +24,14 @@ func TestEntityExpirySnapshotValidation(t *testing.T) {
 	})
 	t.Run("not-enough-history", func(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(participants)
-		rootSnapshot.Encodable().Head.Height += 10 // advance height to be not spork root snapshot
+		rootSnapshot.Encodable().Head().Height += 10 // advance height to be not spork root snapshot
 		err := ValidRootSnapshotContainsEntityExpiryRange(rootSnapshot)
 		require.Error(t, err)
 	})
 	t.Run("enough-history-spork-just-started", func(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(participants)
 		// advance height to be not spork root snapshot, but still lower than transaction expiry
-		rootSnapshot.Encodable().Head.Height += flow.DefaultTransactionExpiry / 2
+		rootSnapshot.Encodable().Head().Height += flow.DefaultTransactionExpiry / 2
 		// add blocks to sealing segment
 		rootSnapshot.Encodable().SealingSegment.ExtraBlocks = unittest.BlockFixtures(int(flow.DefaultTransactionExpiry / 2))
 		err := ValidRootSnapshotContainsEntityExpiryRange(rootSnapshot)
@@ -40,7 +40,7 @@ func TestEntityExpirySnapshotValidation(t *testing.T) {
 	t.Run("enough-history-long-spork", func(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(participants)
 		// advance height to be not spork root snapshot
-		rootSnapshot.Encodable().Head.Height += flow.DefaultTransactionExpiry * 2
+		rootSnapshot.Encodable().Head().Height += flow.DefaultTransactionExpiry * 2
 		// add blocks to sealing segment
 		rootSnapshot.Encodable().SealingSegment.ExtraBlocks = unittest.BlockFixtures(int(flow.DefaultTransactionExpiry) - 1)
 		err := ValidRootSnapshotContainsEntityExpiryRange(rootSnapshot)
@@ -49,7 +49,7 @@ func TestEntityExpirySnapshotValidation(t *testing.T) {
 	t.Run("more-history-than-needed", func(t *testing.T) {
 		rootSnapshot := unittest.RootSnapshotFixture(participants)
 		// advance height to be not spork root snapshot
-		rootSnapshot.Encodable().Head.Height += flow.DefaultTransactionExpiry * 2
+		rootSnapshot.Encodable().Head().Height += flow.DefaultTransactionExpiry * 2
 		// add blocks to sealing segment
 		rootSnapshot.Encodable().SealingSegment.ExtraBlocks = unittest.BlockFixtures(flow.DefaultTransactionExpiry * 2)
 		err := ValidRootSnapshotContainsEntityExpiryRange(rootSnapshot)

state/protocol/inmem/convert.go

@@ -23,15 +23,6 @@ func FromSnapshot(from protocol.Snapshot) (*Snapshot, error) {
 	)
 
 	// convert top-level fields
-	snap.Head, err = from.Head()
-	if err != nil {
-		return nil, fmt.Errorf("could not get head: %w", err)
-	}
-	snap.LatestResult, snap.LatestSeal, err = from.SealedResult()
-	if err != nil {
-		return nil, fmt.Errorf("could not get seal: %w", err)
-	}
-
 	snap.SealingSegment, err = from.SealingSegment()
 	if err != nil {
 		return nil, fmt.Errorf("could not get sealing segment: %w", err)
@@ -218,9 +209,6 @@ func SnapshotFromBootstrapStateWithParams(
 	}
 
 	snap := SnapshotFromEncodable(EncodableSnapshot{
-		Head:         root.Header,
-		LatestSeal:   seal,
-		LatestResult: result,
 		SealingSegment: &flow.SealingSegment{
 			Blocks:           []*flow.Block{root},
 			ExecutionResults: flow.ExecutionResultList{result},

state/protocol/inmem/encodable.go

@@ -8,15 +8,76 @@ import (
 
 // EncodableSnapshot is the encoding format for protocol.Snapshot
 type EncodableSnapshot struct {
-	Head                *flow.Header
-	LatestSeal          *flow.Seal            // TODO replace with same info from sealing segment
-	LatestResult        *flow.ExecutionResult // TODO replace with same info from sealing segment
 	SealingSegment      *flow.SealingSegment
 	QuorumCertificate   *flow.QuorumCertificate
 	Params              EncodableParams
 	SealedVersionBeacon *flow.SealedVersionBeacon
 }
 
+// Head returns the latest finalized header of the Snapshot, which is the block
+// in the sealing segment with the greatest Height.
+// The EncodableSnapshot receiver must be correctly formed.
+func (snap EncodableSnapshot) Head() *flow.Header {
+	return snap.SealingSegment.Highest().Header
+}
+
+// LatestSeal returns the latest seal of the Snapshot. This is the seal
+// for the block with the greatest height, of all seals in the Snapshot.
+// The EncodableSnapshot receiver must be correctly formed.
+func (snap EncodableSnapshot) LatestSeal() *flow.Seal {
+	head := snap.Head()
+	latestSealID := snap.SealingSegment.LatestSeals[head.ID()]
+
+	// CASE 1: The spork root block is the latest sealed block.
+	// By protocol definition, FirstSeal seals the spork root block.
+	if snap.SealingSegment.FirstSeal != nil && snap.SealingSegment.FirstSeal.ID() == latestSealID {
+		return snap.SealingSegment.FirstSeal
+	}
+
+	// CASE 2: For any other snapshot, the latest seal must be in a block payload.
+	// Since seals are included in increasing height order, the latest seal must be in the
+	// first block (by height descending) which contains any seals.
+	for i := len(snap.SealingSegment.Blocks) - 1; i >= 0; i-- {
+		block := snap.SealingSegment.Blocks[i]
+		for _, seal := range block.Payload.Seals {
+			if seal.ID() == latestSealID {
+				return seal
+			}
+		}
+		if len(block.Payload.Seals) > 0 {
+			// We encountered a block with some seals, but not the latest seal.
+			// This can only occur in a structurally invalid SealingSegment.
+			panic("LatestSeal: sanity check failed: no latest seal")
+		}
+	}
+	// Correctly formatted sealing segments must contain latest seal.
+	panic("LatestSeal: unreachable for correctly formatted sealing segments")
+}
+
+// LatestSealedResult returns the latest sealed result of the Snapshot. This is the result which is sealed by LatestSeal.
+// The EncodableSnapshot receiver must be correctly formed.
+func (snap EncodableSnapshot) LatestSealedResult() *flow.ExecutionResult {
+	latestSeal := snap.LatestSeal()
+
+	// For both spork root and mid-spork snapshots, the latest sealing result must
+	// either appear in a block payload or in the ExecutionResults field.
+	for i := len(snap.SealingSegment.Blocks) - 1; i >= 0; i-- {
+		block := snap.SealingSegment.Blocks[i]
+		for _, result := range block.Payload.Results {
+			if latestSeal.ResultID == result.ID() {
+				return result
+			}
+		}
+	}
+	for _, result := range snap.SealingSegment.ExecutionResults {
+		if latestSeal.ResultID == result.ID() {
+			return result
+		}
+	}
+	// Correctly formatted sealing segments must contain latest result.
+	panic("LatestSealedResult: unreachable for correctly formatted sealing segments")
+}
+
 // EncodableDKG is the encoding format for protocol.DKG
 type EncodableDKG struct {
 	GroupKey     encodable.RandomBeaconPubKey

state/protocol/inmem/encodable_test.go

@@ -34,6 +34,6 @@ func TestEncodeDecode(t *testing.T) {
 	require.NoError(t, err)
 
 	// check that the computed and stored result IDs are consistent
-	decodedResult, decodedSeal := decodedSnapshot.LatestResult, decodedSnapshot.LatestSeal
+	decodedResult, decodedSeal := decodedSnapshot.LatestSealedResult(), decodedSnapshot.LatestSeal()
 	assert.Equal(t, decodedResult.ID(), decodedSeal.ResultID)
 }

state/protocol/inmem/snapshot.go

@@ -20,7 +20,7 @@ type Snapshot struct {
 var _ protocol.Snapshot = (*Snapshot)(nil)
 
 func (s Snapshot) Head() (*flow.Header, error) {
-	return s.enc.Head, nil
+	return s.enc.Head(), nil
 }
 
 func (s Snapshot) QuorumCertificate() (*flow.QuorumCertificate, error) {
@@ -50,11 +50,11 @@ func (s Snapshot) Identity(nodeID flow.Identifier) (*flow.Identity, error) {
 }
 
 func (s Snapshot) Commit() (flow.StateCommitment, error) {
-	return s.enc.LatestSeal.FinalState, nil
+	return s.enc.LatestSeal().FinalState, nil
 }
 
 func (s Snapshot) SealedResult() (*flow.ExecutionResult, *flow.Seal, error) {
-	return s.enc.LatestResult, s.enc.LatestSeal, nil
+	return s.enc.LatestSealedResult(), s.enc.LatestSeal(), nil
 }
 
 func (s Snapshot) SealingSegment() (*flow.SealingSegment, error) {

state/protocol/util_test.go

@@ -26,7 +26,7 @@ func TestIsSporkRootSnapshot(t *testing.T) {
 
 	t.Run("other snapshot", func(t *testing.T) {
 		snapshot := unittest.RootSnapshotFixture(unittest.IdentityListFixture(10, unittest.WithAllRoles()))
-		snapshot.Encodable().Head.Height += 1 // modify head height to break equivalence with spork root block height
+		snapshot.Encodable().Head().Height += 1 // modify head height to break equivalence with spork root block height
 		isSporkRoot, err := protocol.IsSporkRootSnapshot(snapshot)
 		require.NoError(t, err)
 		assert.False(t, isSporkRoot)