added db.ValidateWithinTransaction and ValidateNotWithinTransaction

Author: ungerik

db/config.go

@@ -14,8 +14,10 @@ var (
 )
 
 var (
-	conn       = sqldb.ConnectionWithError(context.Background(), errors.New("database connection not initialized"))
-	connCtxKey int
-
+	conn = sqldb.ConnectionWithError(
+		context.Background(),
+		errors.New("database connection not initialized"),
+	)
+	connCtxKey                  int
 	serializedTransactionCtxKey int
 )

db/transaction.go

@@ -12,6 +12,32 @@ import (
 	"github.com/domonda/go-sqldb"
 )
 
+// ValidateWithinTransaction returns sqldb.ErrNotWithinTransaction
+// if the database connection from the context is not a transaction.
+func ValidateWithinTransaction(ctx context.Context) error {
+	conn := Conn(ctx)
+	if err := conn.Config().Err; err != nil {
+		return err
+	}
+	if !conn.IsTransaction() {
+		return sqldb.ErrNotWithinTransaction
+	}
+	return nil
+}
+
+// ValidateNotWithinTransaction returns sqldb.ErrWithinTransaction
+// if the database connection from the context is a transaction.
+func ValidateNotWithinTransaction(ctx context.Context) error {
+	conn := Conn(ctx)
+	if err := conn.Config().Err; err != nil {
+		return err
+	}
+	if conn.IsTransaction() {
+		return sqldb.ErrWithinTransaction
+	}
+	return nil
+}
+
 // DebugNoTransaction executes nonTxFunc without a database transaction.
 // Useful to temporarely replace Transaction to debug the same code without using a transaction.
 func DebugNoTransaction(ctx context.Context, nonTxFunc func(context.Context) error) error {

mockconn/connection.go

@@ -69,7 +69,7 @@ func (conn *connection) Stats() sql.DBStats {
 }
 
 func (conn *connection) Config() *sqldb.Config {
-	return &sqldb.Config{Driver: "mockconn"}
+	return &sqldb.Config{Driver: "mockconn", Host: "localhost", Database: "mock"}
 }
 
 func (conn *connection) Ping(time.Duration) error {