Savepoint API.

conn.go

@@ -332,6 +332,6 @@ type DriverConn interface {
 	driver.ExecerContext
 	driver.ConnPrepareContext
 
-	Savepoint() (release func(*error))
+	Savepoint() Savepoint
 	OpenBlob(db, table, column string, row int64, write bool) (*Blob, error)
 }

driver/driver.go

@@ -189,7 +189,7 @@ func (c conn) ExecContext(ctx context.Context, query string, args []driver.Named
 	}, nil
 }
 
-func (c conn) Savepoint() (release func(*error)) {
+func (c conn) Savepoint() sqlite3.Savepoint {
 	return c.conn.Savepoint()
 }
 

driver_test.go

@@ -48,7 +48,8 @@ func ExampleDriverConn() {
 
 	err = conn.Raw(func(driverConn any) error {
 		conn := driverConn.(sqlite3.DriverConn)
-		defer conn.Savepoint()(&err)
+		savept := conn.Savepoint()
+		defer savept.Release(&err)
 
 		blob, err := conn.OpenBlob("main", "test", "col", id, true)
 		if err != nil {

tests/tx_test.go

@@ -185,10 +185,10 @@ func TestConn_Transaction_interrupt(t *testing.T) {
 		t.Errorf("got %v, want sqlite3.INTERRUPT", err)
 	}
 
-	var nilErr error
-	tx.End(&nilErr)
-	if !errors.Is(nilErr, sqlite3.INTERRUPT) {
-		t.Errorf("got %v, want sqlite3.INTERRUPT", nilErr)
+	err = nil
+	tx.End(&err)
+	if !errors.Is(err, sqlite3.INTERRUPT) {
+		t.Errorf("got %v, want sqlite3.INTERRUPT", err)
 	}
 
 	db.SetInterrupt(context.Background())
@@ -210,6 +210,33 @@ func TestConn_Transaction_interrupt(t *testing.T) {
 	}
 }
 
+func TestConn_Transaction_interrupted(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	db.SetInterrupt(ctx)
+	cancel()
+
+	tx := db.Begin()
+
+	err = tx.Commit()
+	if !errors.Is(err, sqlite3.INTERRUPT) {
+		t.Errorf("got %v, want sqlite3.INTERRUPT", err)
+	}
+
+	err = nil
+	tx.End(&err)
+	if !errors.Is(err, sqlite3.INTERRUPT) {
+		t.Errorf("got %v, want sqlite3.INTERRUPT", err)
+	}
+}
+
 func TestConn_Transaction_rollback(t *testing.T) {
 	t.Parallel()
 
@@ -286,7 +313,7 @@ func TestConn_Savepoint_exec(t *testing.T) {
 	}
 
 	insert := func(succeed bool) (err error) {
-		defer db.Savepoint()(&err)
+		defer db.Savepoint().Release(&err)
 
 		err = db.Exec(`INSERT INTO test VALUES ('hello')`)
 		if err != nil {
@@ -344,7 +371,7 @@ func TestConn_Savepoint_panic(t *testing.T) {
 	}
 
 	panics := func() (err error) {
-		defer db.Savepoint()(&err)
+		defer db.Savepoint().Release(&err)
 
 		err = db.Exec(`INSERT INTO test VALUES ('hello')`)
 		if err != nil {
@@ -395,12 +422,12 @@ func TestConn_Savepoint_interrupt(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	release := db.Savepoint()
+	savept := db.Savepoint()
 	err = db.Exec(`INSERT INTO test VALUES (1)`)
 	if err != nil {
 		t.Fatal(err)
 	}
-	release(&err)
+	savept.Release(&err)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -408,19 +435,19 @@ func TestConn_Savepoint_interrupt(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	db.SetInterrupt(ctx)
 
-	release1 := db.Savepoint()
+	savept1 := db.Savepoint()
 	err = db.Exec(`INSERT INTO test VALUES (2)`)
 	if err != nil {
 		t.Fatal(err)
 	}
-	release2 := db.Savepoint()
+	savept2 := db.Savepoint()
 	err = db.Exec(`INSERT INTO test VALUES (3)`)
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	cancel()
-	db.Savepoint()(&err)
+	db.Savepoint().Release(&err)
 	if !errors.Is(err, sqlite3.INTERRUPT) {
 		t.Errorf("got %v, want sqlite3.INTERRUPT", err)
 	}
@@ -431,15 +458,15 @@ func TestConn_Savepoint_interrupt(t *testing.T) {
 	}
 
 	err = context.Canceled
-	release2(&err)
+	savept2.Release(&err)
 	if err != context.Canceled {
 		t.Fatal(err)
 	}
 
-	var nilErr error
-	release1(&nilErr)
-	if !errors.Is(nilErr, sqlite3.INTERRUPT) {
-		t.Errorf("got %v, want sqlite3.INTERRUPT", nilErr)
+	err = nil
+	savept1.Release(&err)
+	if !errors.Is(err, sqlite3.INTERRUPT) {
+		t.Errorf("got %v, want sqlite3.INTERRUPT", err)
 	}
 
 	db.SetInterrupt(context.Background())
@@ -475,7 +502,7 @@ func TestConn_Savepoint_rollback(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	release := db.Savepoint()
+	savept := db.Savepoint()
 	err = db.Exec(`INSERT INTO test VALUES (1)`)
 	if err != nil {
 		t.Fatal(err)
@@ -484,7 +511,7 @@ func TestConn_Savepoint_rollback(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	release(&err)
+	savept.Release(&err)
 	if err != nil {
 		t.Fatal(err)
 	}

tx.go

@@ -4,10 +4,14 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/rand"
 	"runtime"
+	"strconv"
 )
 
 // Tx is an in-progress database transaction.
+//
+// https://www.sqlite.org/lang_transaction.html
 type Tx struct {
 	c *Conn
 }
@@ -16,8 +20,9 @@ type Tx struct {
 //
 // https://www.sqlite.org/lang_transaction.html
 func (c *Conn) Begin() Tx {
-	err := c.Exec(`BEGIN DEFERRED`)
-	if err != nil && !errors.Is(err, INTERRUPT) {
+	// BEGIN even if interrupted.
+	err := c.txExecInterrupted(`BEGIN DEFERRED`)
+	if err != nil {
 		panic(err)
 	}
 	return Tx{c}
@@ -64,21 +69,22 @@ func (tx Tx) End(errp *error) {
 		defer panic(recovered)
 	}
 
-	if tx.c.GetAutocommit() {
-		// There is nothing to commit/rollback.
-		return
-	}
-
-	if *errp == nil && recovered == nil {
+	if (errp == nil || *errp == nil) && recovered == nil {
 		// Success path.
+		if tx.c.GetAutocommit() { // There is nothing to commit.
+			return
+		}
 		*errp = tx.Commit()
 		if *errp == nil {
 			return
 		}
-		// Possible interrupt, fall through to the error path.
+		// Fall through to the error path.
 	}
 
 	// Error path.
+	if tx.c.GetAutocommit() { // There is nothing to rollback.
+		return
+	}
 	err := tx.Rollback()
 	if err != nil {
 		panic(err)
@@ -92,33 +98,28 @@ func (tx Tx) Commit() error {
 	return tx.c.Exec(`COMMIT`)
 }
 
-// Rollback rolls back the transaction.
+// Rollback rolls back the transaction,
+// even if the connection has been interrupted.
 //
 // https://www.sqlite.org/lang_transaction.html
 func (tx Tx) Rollback() error {
-	// ROLLBACK even if the connection has been interrupted.
-	old := tx.c.SetInterrupt(context.Background())
-	defer tx.c.SetInterrupt(old)
-	return tx.c.Exec(`ROLLBACK`)
+	return tx.c.txExecInterrupted(`ROLLBACK`)
 }
 
-// Savepoint creates a named SQLite transaction using SAVEPOINT.
-//
-// On success Savepoint returns a release func that will call either
-// RELEASE or ROLLBACK depending on whether the parameter *error
-// points to a nil or non-nil error.
-//
-// This is meant to be deferred:
-//
-//	func doWork(conn *sqlite3.Conn) (err error) {
-//		defer conn.Savepoint()(&err)
-//
-//		// ... do work in the transaction
-//	}
+// Savepoint is a marker within a transaction
+// that allows for partial rollback.
 //
 // https://www.sqlite.org/lang_savepoint.html
-func (c *Conn) Savepoint() (release func(*error)) {
-	name := "sqlite3.Savepoint" // names can be reused
+type Savepoint struct {
+	c    *Conn
+	name string
+}
+
+// Savepoint establishes a new transaction savepoint.
+//
+// https://www.sqlite.org/lang_savepoint.html
+func (c *Conn) Savepoint() Savepoint {
+	name := "sqlite3.Savepoint"
 	var pc [1]uintptr
 	if n := runtime.Callers(2, pc[:]); n > 0 {
 		frames := runtime.CallersFrames(pc[:n])
@@ -127,52 +128,75 @@ func (c *Conn) Savepoint() (release func(*error)) {
 			name = frame.Function
 		}
 	}
+	// Names can be reused; this makes catching bugs more likely.
+	name += "#" + strconv.Itoa(int(rand.Int31()))
 
-	err := c.Exec(fmt.Sprintf("SAVEPOINT %q;", name))
+	err := c.txExecInterrupted(fmt.Sprintf("SAVEPOINT %q;", name))
 	if err != nil {
-		if errors.Is(err, INTERRUPT) {
-			return func(errp *error) {
-				if *errp == nil {
-					*errp = err
-				}
-			}
-		}
 		panic(err)
 	}
+	return Savepoint{c: c, name: name}
+}
 
-	return func(errp *error) {
-		recovered := recover()
-		if recovered != nil {
-			defer panic(recovered)
-		}
+// Release releases the savepoint rolling back any changes
+// if *error points to a non-nil error.
+//
+// This is meant to be deferred:
+//
+//	func doWork(conn *sqlite3.Conn) (err error) {
+//		savept := conn.Savepoint()
+//		defer savept.Release(&err)
+//
+//		// ... do work in the transaction
+//	}
+func (s Savepoint) Release(errp *error) {
+	recovered := recover()
+	if recovered != nil {
+		defer panic(recovered)
+	}
 
-		if c.GetAutocommit() {
-			// There is nothing to commit/rollback.
+	if (errp == nil || *errp == nil) && recovered == nil {
+		// Success path.
+		if s.c.GetAutocommit() { // There is nothing to commit.
 			return
 		}
-
-		if *errp == nil && recovered == nil {
-			// Success path.
-			// RELEASE the savepoint successfully.
-			*errp = c.Exec(fmt.Sprintf("RELEASE %q;", name))
-			if *errp == nil {
-				return
-			}
-			// Possible interrupt, fall through to the error path.
+		*errp = s.c.Exec(fmt.Sprintf("RELEASE %q;", s.name))
+		if *errp == nil {
+			return
 		}
+		// Fall through to the error path.
+	}
 
-		// Error path.
-		// Always ROLLBACK even if the connection has been interrupted.
-		old := c.SetInterrupt(context.Background())
-		defer c.SetInterrupt(old)
-
-		err := c.Exec(fmt.Sprintf("ROLLBACK TO %q;", name))
-		if err != nil {
-			panic(err)
-		}
-		err = c.Exec(fmt.Sprintf("RELEASE %q;", name))
-		if err != nil {
-			panic(err)
-		}
+	// Error path.
+	if s.c.GetAutocommit() { // There is nothing to rollback.
+		return
+	}
+	// ROLLBACK and RELEASE even if interrupted.
+	err := s.c.txExecInterrupted(fmt.Sprintf(`
+		ROLLBACK TO %[1]q;
+		RELEASE %[1]q;
+	`, s.name))
+	if err != nil {
+		panic(err)
 	}
 }
+
+// Rollback rolls the transaction back to the savepoint,
+// even if the connection has been interrupted.
+// Rollback does not release the savepoint.
+//
+// https://www.sqlite.org/lang_transaction.html
+func (s Savepoint) Rollback() error {
+	// ROLLBACK even if interrupted.
+	return s.c.txExecInterrupted(fmt.Sprintf("ROLLBACK TO %q;", s.name))
+}
+
+func (c *Conn) txExecInterrupted(sql string) error {
+	err := c.Exec(sql)
+	if errors.Is(err, INTERRUPT) {
+		old := c.SetInterrupt(context.Background())
+		defer c.SetInterrupt(old)
+		err = c.Exec(sql)
+	}
+	return err
+}