asset: update DeepEqual to work with asset v1 (segwit)

The asset version v1 (segwit) allows an asset to be committed without
the TxWitness field. Therefore, when comparing two such assets, we must
also ignore the TxWitness field.

If we don't do this, then the deep equal check when creating a proof for
a split asset fails when checking if the split root asset was committed
to the root tree.

Author: guggero

asset/asset.go

@@ -426,8 +426,10 @@ func (w *Witness) Decode(r io.Reader) error {
 	return stream.Decode(r)
 }
 
-// DeepEqual returns true if this witness is equal with the given witness.
-func (w *Witness) DeepEqual(o *Witness) bool {
+// DeepEqual returns true if this witness is equal with the given witness. If
+// the skipTxWitness boolean is set, the TxWitness field of the Witness is not
+// compared.
+func (w *Witness) DeepEqual(skipTxWitness bool, o *Witness) bool {
 	if w == nil || o == nil {
 		return w == o
 	}
@@ -436,11 +438,17 @@ func (w *Witness) DeepEqual(o *Witness) bool {
 		return false
 	}
 
-	if !reflect.DeepEqual(w.TxWitness, o.TxWitness) {
+	if !w.SplitCommitment.DeepEqual(o.SplitCommitment) {
 		return false
 	}
 
-	return w.SplitCommitment.DeepEqual(o.SplitCommitment)
+	// If we're not comparing the TxWitness, we're done. This might be
+	// useful when comparing witnesses of segregated witness version assets.
+	if skipTxWitness {
+		return true
+	}
+
+	return reflect.DeepEqual(w.TxWitness, o.TxWitness)
 }
 
 // ScriptVersion denotes the asset script versioning scheme.
@@ -1398,6 +1406,20 @@ func (a *Asset) Copy() *Asset {
 
 // DeepEqual returns true if this asset is equal with the given asset.
 func (a *Asset) DeepEqual(o *Asset) bool {
+	return a.deepEqual(false, o)
+}
+
+// DeepEqualAllowSegWitIgnoreTxWitness returns true if this asset is equal with
+// the given asset, ignoring the TxWitness field of the Witness if the asset
+// version is v1.
+func (a *Asset) DeepEqualAllowSegWitIgnoreTxWitness(o *Asset) bool {
+	return a.deepEqual(true, o)
+}
+
+// deepEqual returns true if this asset is equal with the given asset. The
+// allowSegWitIgnoreTxWitness flag is used to determine whether the TxWitness
+// field of the Witness should be ignored if the asset version is v1.
+func (a *Asset) deepEqual(allowSegWitIgnoreTxWitness bool, o *Asset) bool {
 	if a.Version != o.Version {
 		return false
 	}
@@ -1437,7 +1459,9 @@ func (a *Asset) DeepEqual(o *Asset) bool {
 	}
 
 	for i := range a.PrevWitnesses {
-		if !a.PrevWitnesses[i].DeepEqual(&o.PrevWitnesses[i]) {
+		oPrevWitness := &o.PrevWitnesses[i]
+		skipTxWitness := a.Version == V1 && allowSegWitIgnoreTxWitness
+		if !a.PrevWitnesses[i].DeepEqual(skipTxWitness, oPrevWitness) {
 			return false
 		}
 	}

proof/append.go

@@ -166,7 +166,13 @@ func CreateTransitionProof(prevOut wire.OutPoint,
 		}
 
 		// Make sure the committed asset matches the root asset exactly.
-		if !committedRoot.DeepEqual(rootAsset) {
+		// We allow the TxWitness to mismatch for assets with version 1
+		// as they would not include the witness when the proof is
+		// created.
+		if !committedRoot.DeepEqualAllowSegWitIgnoreTxWitness(
+			rootAsset,
+		) {
+
 			return nil, fmt.Errorf("root asset mismatch")
 		}