upd

interface.go

@@ -3,7 +3,6 @@ package header
 import (
 	"context"
 	"errors"
-	"fmt"
 
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
 )
@@ -59,16 +58,6 @@ var (
 	ErrHeadersLimitExceeded = errors.New("header/p2p: header limit per 1 request exceeded")
 )
 
-// ErrNonAdjacent is returned when Store is appended with a header not adjacent to the stored head.
-type ErrNonAdjacent struct {
-	Head      uint64
-	Attempted uint64
-}
-
-func (ena *ErrNonAdjacent) Error() string {
-	return fmt.Sprintf("header/store: non-adjacent: head %d, attempted %d", ena.Head, ena.Attempted)
-}
-
 // Store encompasses the behavior necessary to store and retrieve Headers
 // from a node's local storage.
 type Store[H Header[H]] interface {
@@ -88,10 +77,6 @@ type Store[H Header[H]] interface {
 	HasAt(context.Context, uint64) bool
 
 	// Append stores and verifies the given Header(s).
-	// It requires them to be adjacent and in ascending order,
-	// as it applies them contiguously on top of the current head height.
-	// It returns the amount of successfully applied headers,
-	// so caller can understand what given header was invalid, if any.
 	Append(context.Context, ...H) error
 
 	// GetRange returns the range [from:to).

store/store.go

@@ -330,14 +330,6 @@ func (s *Store[H]) Append(ctx context.Context, headers ...H) error {
 	// collect valid headers
 	verified := make([]H, 0, lh)
 	for i, h := range headers {
-		// currently store requires all headers to be appended sequentially and adjacently
-		// TODO(@Wondertan): Further pruning friendly Store design should reevaluate this requirement
-		if h.Height() != head.Height()+1 {
-			return &header.ErrNonAdjacent{
-				Head:      head.Height(),
-				Attempted: h.Height(),
-			}
-		}
 
 		err = head.Verify(h)
 		if err != nil {
@@ -358,7 +350,8 @@ func (s *Store[H]) Append(ctx context.Context, headers ...H) error {
 			// otherwise, stop the loop and apply headers appeared to be valid
 			break
 		}
-		verified, head = append(verified, h), h
+		verified = append(verified, h)
+		head = h
 	}
 
 	onWrite := func() {

sync/sync_head.go

@@ -114,13 +114,8 @@ func (s *Syncer[H]) subjectiveHead(ctx context.Context) (H, error) {
 
 // setSubjectiveHead takes already validated head and sets it as the new sync target.
 func (s *Syncer[H]) setSubjectiveHead(ctx context.Context, netHead H) {
-	// TODO(@Wondertan): Right now, we can only store adjacent headers, instead we should:
-	//  * Allow storing any valid header here in Store
-	//  * Remove ErrNonAdjacent
-	//  * Remove writeHead from the canonical store implementation
 	err := s.storeHeaders(ctx, netHead)
-	var nonAdj *header.ErrNonAdjacent
-	if err != nil && !errors.As(err, &nonAdj) {
+	if err != nil {
 		// might be a storage error or something else, but we can still try to continue processing netHead
 		log.Errorw("storing new network header",
 			"height", netHead.Height(),