Don't overwrite global err before return (#1293)

Signed-off-by: Olivier Charvin <git@olivier.pfad.fr>

2 files changed, 24 insertions, 20 deletions

diff --git a/internal/sqlutil/partition_offset_table.go b/internal/sqlutil/partition_offset_table.go
index be079442..e19a092f 100644
--- a/internal/sqlutil/partition_offset_table.go
+++ b/internal/sqlutil/partition_offset_table.go
@@ -18,8 +18,6 @@ import (
 	"context"
 	"database/sql"
 	"strings"
-
-	"github.com/matrix-org/util"
 )
 
 // A PartitionOffset is the offset into a partition of the input log.
@@ -99,26 +97,28 @@ func (s *PartitionOffsetStatements) SetPartitionOffset(
 // selectPartitionOffsets returns all the partition offsets for the given topic.
 func (s *PartitionOffsetStatements) selectPartitionOffsets(
 	ctx context.Context, topic string,
-) ([]PartitionOffset, error) {
+) (results []PartitionOffset, err error) {
 	rows, err := s.selectPartitionOffsetsStmt.QueryContext(ctx, topic)
 	if err != nil {
 		return nil, err
 	}
-	defer func() {
-		err2 := rows.Close()
-		if err2 != nil {
-			util.GetLogger(ctx).WithError(err2).Error("selectPartitionOffsets: rows.close() failed")
-		}
-	}()
-	var results []PartitionOffset
+	defer checkNamedErr(rows.Close, &err)
 	for rows.Next() {
 		var offset PartitionOffset
-		if err := rows.Scan(&offset.Partition, &offset.Offset); err != nil {
+		if err = rows.Scan(&offset.Partition, &offset.Offset); err != nil {
 			return nil, err
 		}
 		results = append(results, offset)
 	}
-	return results, rows.Err()
+	err = rows.Err()
+	return results, err
+}
+
+// checkNamedErr calls fn and overwrite err if it was nil and fn returned non-nil
+func checkNamedErr(fn func() error, err *error) {
+	if e := fn(); e != nil && *err == nil {
+		*err = e
+	}
 }
 
 // UpsertPartitionOffset updates or inserts the partition offset for the given topic.
diff --git a/internal/sqlutil/sql.go b/internal/sqlutil/sql.go
index d296c418..1d2825d5 100644
--- a/internal/sqlutil/sql.go
+++ b/internal/sqlutil/sql.go
@@ -38,9 +38,18 @@ type Transaction interface {
 // was applied correctly. For example, 'database is locked' errors in sqlite will happen here.
 func EndTransaction(txn Transaction, succeeded *bool) error {
 	if *succeeded {
-		return txn.Commit() // nolint: errcheck
+		return txn.Commit()
 	} else {
-		return txn.Rollback() // nolint: errcheck
+		return txn.Rollback()
+	}
+}
+
+// EndTransactionWithCheck ends a transaction and overwrites the error pointer if its value was nil.
+// If the transaction succeeded then it is committed, otherwise it is rolledback.
+// Designed to be used with defer (see EndTransaction otherwise).
+func EndTransactionWithCheck(txn Transaction, succeeded *bool, err *error) {
+	if e := EndTransaction(txn, succeeded); e != nil && *err == nil {
+		*err = e
 	}
 }
 
@@ -53,12 +62,7 @@ func WithTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
 		return fmt.Errorf("sqlutil.WithTransaction.Begin: %w", err)
 	}
 	succeeded := false
-	defer func() {
-		err2 := EndTransaction(txn, &succeeded)
-		if err == nil && err2 != nil { // failed to commit/rollback
-			err = err2
-		}
-	}()
+	defer EndTransactionWithCheck(txn, &succeeded, &err)
 
 	err = fn(txn)
 	if err != nil {