refactor: Remove discard return value (#71)

## Relevant issue(s)

Resolves #70

## Description

Removes the discard return value, as no implementations ever return a
value and it made calling `Discard` in a `defer` undesirable (requires
ignoring potential errors, and adding a `//nolint`).

Author: AndrewSisley

badger/badger.go

@@ -44,41 +44,37 @@ func NewDatastoreFrom(db *badger.DB) *Datastore {
 
 func (b *Datastore) Get(ctx context.Context, key []byte) ([]byte, error) {
 	txn := b.newTxn(true)
+	defer txn.Discard()
 
-	result, err := txn.Get(ctx, key)
-	dErr := txn.Discard()
-
-	return result, errors.Join(err, dErr)
+	return txn.Get(ctx, key)
 }
 
 func (b *Datastore) Has(ctx context.Context, key []byte) (bool, error) {
 	txn := b.newTxn(true)
+	defer txn.Discard()
 
-	result, err := txn.Has(ctx, key)
-	dErr := txn.Discard()
-
-	return result, errors.Join(err, dErr)
+	return txn.Has(ctx, key)
 }
 
 func (b *Datastore) Set(ctx context.Context, key []byte, value []byte) error {
 	txn := b.newTxn(false)
+	defer txn.Discard()
 
 	err := txn.Set(ctx, key, value)
 	if err != nil {
-		dErr := txn.Discard()
-		return errors.Join(err, dErr)
+		return err
 	}
 
 	return txn.Commit()
 }
 
 func (b *Datastore) Delete(ctx context.Context, key []byte) error {
 	txn := b.newTxn(false)
+	defer txn.Discard()
 
 	err := txn.Delete(ctx, key)
 	if err != nil {
-		dErr := txn.Discard()
-		return errors.Join(err, dErr)
+		return err
 	}
 
 	return txn.Commit()
@@ -104,7 +100,8 @@ func (b *Datastore) Iterator(ctx context.Context, iterOpts corekv.IterOptions) (
 	// so that the txn is discarded when the
 	// iterator is closed
 	it.withCloser(func() error {
-		return txn.Discard()
+		txn.Discard()
+		return nil
 	})
 
 	return it, nil
@@ -183,13 +180,13 @@ func (txn *bTxn) Commit() error {
 	return badgerErrToKVErr(err)
 }
 
-func (txn *bTxn) Discard() error {
+func (txn *bTxn) Discard() {
 	txn.t.Discard()
-	return nil
 }
 
 func (t *bTxn) Close() error {
-	return t.Discard()
+	t.Discard()
+	return nil
 }
 
 var badgerErrToKVErrMap = map[error]error{

kv.go

@@ -167,5 +167,5 @@ type Txn interface {
 
 	// Discard discards all changes made via this object so far, returning
 	// it to the state it was at at time of construction.
-	Discard() error
+	Discard()
 }

memory/txn.go

@@ -321,20 +321,19 @@ func (iter *txnIterator) Close() error {
 }
 
 func (t *basicTxn) Close() error {
-	return t.Discard()
+	t.Discard()
+	return nil
 }
 
 // Discard removes all the operations added to the transaction.
-func (t *basicTxn) Discard() error {
+func (t *basicTxn) Discard() {
 	if t.discarded {
-		return nil
+		return
 	}
 
 	t.ops.Clear()
 	t.clearInFlightTxn()
 	t.discarded = true
-
-	return nil
 }
 
 // Commit saves the operations to the underlying datastore.

namespace/namespace.go

@@ -181,8 +181,8 @@ func (txn *Txn) Commit() error {
 	return txn.txn.Commit()
 }
 
-func (txn *Txn) Discard() error {
-	return txn.txn.Discard()
+func (txn *Txn) Discard() {
+	txn.txn.Discard()
 }
 
 func cp(bz []byte) (ret []byte) {

test/action/txn.go

@@ -127,8 +127,7 @@ func DiscardI(id int) *DiscardTxn {
 func (a *DiscardTxn) Execute(s *state.State) {
 	txn := s.Txns[a.ID]
 
-	err := txn.Discard()
-	require.NoError(s.T, err)
+	txn.Discard()
 }
 
 // CommitTxn commits the given transaction when executed.