Remove Decided from the Consensus interface (#3123)

snow/consensus/snowman/consensus.go

@@ -39,9 +39,6 @@ type Consensus interface {
 	// Returns if a critical error has occurred.
 	Add(Block) error
 
-	// Decided returns true if the block has been decided.
-	Decided(Block) bool
-
 	// Processing returns true if the block ID is currently processing.
 	Processing(ids.ID) bool
 

snow/consensus/snowman/consensus_test.go

@@ -291,7 +291,6 @@ func StatusOrProcessingPreviouslyAcceptedTest(t *testing.T, factory Factory) {
 
 	require.Equal(choices.Accepted, snowmantest.Genesis.Status())
 	require.False(sm.Processing(snowmantest.Genesis.ID()))
-	require.True(sm.Decided(snowmantest.Genesis))
 	require.True(sm.IsPreferred(snowmantest.Genesis.ID()))
 
 	pref, ok := sm.PreferenceAtHeight(snowmantest.Genesis.Height())
@@ -329,7 +328,6 @@ func StatusOrProcessingPreviouslyRejectedTest(t *testing.T, factory Factory) {
 
 	require.Equal(choices.Rejected, block.Status())
 	require.False(sm.Processing(block.ID()))
-	require.True(sm.Decided(block))
 	require.False(sm.IsPreferred(block.ID()))
 
 	_, ok := sm.PreferenceAtHeight(block.Height())
@@ -365,7 +363,6 @@ func StatusOrProcessingUnissuedTest(t *testing.T, factory Factory) {
 
 	require.Equal(choices.Processing, block.Status())
 	require.False(sm.Processing(block.ID()))
-	require.False(sm.Decided(block))
 	require.False(sm.IsPreferred(block.ID()))
 
 	_, ok := sm.PreferenceAtHeight(block.Height())
@@ -402,7 +399,6 @@ func StatusOrProcessingIssuedTest(t *testing.T, factory Factory) {
 	require.NoError(sm.Add(block))
 	require.Equal(choices.Processing, block.Status())
 	require.True(sm.Processing(block.ID()))
-	require.False(sm.Decided(block))
 	require.True(sm.IsPreferred(block.ID()))
 
 	pref, ok := sm.PreferenceAtHeight(block.Height())

snow/consensus/snowman/topological.go

@@ -13,7 +13,6 @@ import (
 
 	"github.com/ava-labs/avalanchego/ids"
 	"github.com/ava-labs/avalanchego/snow"
-	"github.com/ava-labs/avalanchego/snow/choices"
 	"github.com/ava-labs/avalanchego/snow/consensus/snowball"
 	"github.com/ava-labs/avalanchego/utils/bag"
 	"github.com/ava-labs/avalanchego/utils/set"
@@ -182,16 +181,6 @@ func (ts *Topological) Add(blk Block) error {
 	return nil
 }
 
-func (ts *Topological) Decided(blk Block) bool {
-	// If the block is decided, then it must have been previously issued.
-	if blk.Status().Decided() {
-		return true
-	}
-	// If the block is marked as fetched, we can check if it has been
-	// transitively rejected.
-	return blk.Status() == choices.Processing && blk.Height() <= ts.lastAcceptedHeight
-}
-
 func (ts *Topological) Processing(blkID ids.ID) bool {
 	// The last accepted block is in the blocks map, so we first must ensure the
 	// requested block isn't the last accepted block.

snow/engine/snowman/transitive.go

@@ -758,7 +758,7 @@ func (t *Transitive) issueFrom(
 		delete(t.blkReqSourceMetric, req)
 	}
 
-	issued := t.Consensus.Decided(blk) || t.Consensus.Processing(blkID)
+	issued := t.isDecided(blk) || t.Consensus.Processing(blkID)
 	if issued {
 		// A dependency should never be waiting on a decided or processing
 		// block. However, if the block was marked as rejected by the VM, the
@@ -794,7 +794,7 @@ func (t *Transitive) issueWithAncestors(
 	}
 
 	// The block was issued into consensus. This is the happy path.
-	if status != choices.Unknown && (t.Consensus.Decided(blk) || t.Consensus.Processing(blkID)) {
+	if status != choices.Unknown && (t.isDecided(blk) || t.Consensus.Processing(blkID)) {
 		return true, nil
 	}
 
@@ -815,7 +815,7 @@ func (t *Transitive) issueWithAncestors(
 // If the block is queued to be added to consensus, then it was issued.
 func (t *Transitive) wasIssued(blk snowman.Block) bool {
 	blkID := blk.ID()
-	return t.Consensus.Decided(blk) || t.Consensus.Processing(blkID) || t.pendingContains(blkID)
+	return t.isDecided(blk) || t.Consensus.Processing(blkID) || t.pendingContains(blkID)
 }
 
 // Issue [blk] to consensus once its ancestors have been issued.
@@ -849,7 +849,7 @@ func (t *Transitive) issue(
 
 	// block on the parent if needed
 	parentID := blk.Parent()
-	if parent, err := t.getBlock(ctx, parentID); err != nil || !(t.Consensus.Decided(parent) || t.Consensus.Processing(parentID)) {
+	if parent, err := t.getBlock(ctx, parentID); err != nil || !(t.isDecided(parent) || t.Consensus.Processing(parentID)) {
 		t.Ctx.Log.Verbo("block waiting for parent to be issued",
 			zap.Stringer("blkID", blkID),
 			zap.Stringer("parentID", parentID),
@@ -958,7 +958,7 @@ func (t *Transitive) deliver(
 	t.removeFromPending(blk)
 
 	blkID := blk.ID()
-	if t.Consensus.Decided(blk) || t.Consensus.Processing(blkID) {
+	if t.isDecided(blk) || t.Consensus.Processing(blkID) {
 		// If [blk] is decided, then it shouldn't be added to consensus.
 		// Similarly, if [blkID] is already in the processing set, it shouldn't
 		// be added to consensus again.
@@ -1073,7 +1073,7 @@ func (t *Transitive) removeFromPending(blk snowman.Block) {
 func (t *Transitive) addToNonVerifieds(blk snowman.Block) {
 	// don't add this blk if it's decided or processing.
 	blkID := blk.ID()
-	if t.Consensus.Decided(blk) || t.Consensus.Processing(blkID) {
+	if t.isDecided(blk) || t.Consensus.Processing(blkID) {
 		return
 	}
 	parentID := blk.Parent()
@@ -1163,7 +1163,7 @@ func (t *Transitive) getProcessingAncestor(ctx context.Context, initialVote ids.
 			return ids.Empty, false
 		}
 
-		if t.Consensus.Decided(blk) {
+		if t.isDecided(blk) {
 			t.Ctx.Log.Debug("dropping vote",
 				zap.String("reason", "bubbled vote already decided"),
 				zap.Stringer("initialVoteID", initialVote),
@@ -1178,3 +1178,15 @@ func (t *Transitive) getProcessingAncestor(ctx context.Context, initialVote ids.
 		bubbledVote = blk.Parent()
 	}
 }
+
+// isDecided reports true if the provided block's status is Accepted, Rejected,
+// or if the block's height implies that the block is either Accepted or
+// Rejected.
+func (t *Transitive) isDecided(blk snowman.Block) bool {
+	if blk.Status().Decided() {
+		return true
+	}
+
+	_, lastAcceptedHeight := t.Consensus.LastAccepted()
+	return blk.Height() <= lastAcceptedHeight
+}