JSON support.

README.md

@@ -82,7 +82,7 @@ Performance is tested by running
   - [x] nested transactions
   - [x] incremental BLOB I/O
   - [x] online backup
-  - [ ] JSON support
+  - [x] JSON support
   - [ ] session extension
 - [ ] custom VFSes
   - [x] custom VFS API

driver/driver.go

@@ -30,6 +30,7 @@ import (
 	"context"
 	"database/sql"
 	"database/sql/driver"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/url"
@@ -272,6 +273,10 @@ func (c *conn) ExecContext(ctx context.Context, query string, args []driver.Name
 	return newResult(c.Conn), nil
 }
 
+func (*conn) CheckNamedValue(arg *driver.NamedValue) error {
+	return nil
+}
+
 type stmt struct {
 	Stmt *sqlite3.Stmt
 	Conn *sqlite3.Conn
@@ -370,6 +375,8 @@ func (s *stmt) setupBindings(args []driver.NamedValue) error {
 				err = s.Stmt.BindZeroBlob(id, int64(a))
 			case time.Time:
 				err = s.Stmt.BindTime(id, a, sqlite3.TimeFormatDefault)
+			case json.Marshaler:
+				err = s.Stmt.BindJSON(id, a)
 			case nil:
 				err = s.Stmt.BindNull(id)
 			default:
@@ -386,7 +393,7 @@ func (s *stmt) setupBindings(args []driver.NamedValue) error {
 func (s *stmt) CheckNamedValue(arg *driver.NamedValue) error {
 	switch arg.Value.(type) {
 	case bool, int, int64, float64, string, []byte,
-		sqlite3.ZeroBlob, time.Time, nil:
+		sqlite3.ZeroBlob, time.Time, json.Marshaler, nil:
 		return nil
 	default:
 		return driver.ErrSkip

json.go

@@ -0,0 +1,53 @@
+package sqlite3
+
+import (
+	"encoding/json"
+	"strconv"
+	"time"
+	"unsafe"
+)
+
+// JSON returns:
+// a [json.Marshaler] that can be used as an argument to
+// [database/sql.DB.Exec] and similar methods to
+// store value as JSON; and
+// a [database/sql.Scanner] that can be used as an argument to
+// [database/sql.Row.Scan] and similar methods to
+// decode JSON into value.
+func JSON(value any) any {
+	return jsonValue{value}
+}
+
+type jsonValue struct{ any }
+
+func (j jsonValue) MarshalJSON() ([]byte, error) {
+	return json.Marshal(j.any)
+}
+
+func (j jsonValue) UnmarshalJSON(data []byte) error {
+	return json.Unmarshal(data, j.any)
+}
+
+func (j jsonValue) Scan(value any) error {
+	var mem [40]byte
+	buf := mem[:0]
+
+	switch v := value.(type) {
+	case []byte:
+		buf = v
+	case string:
+		buf = unsafe.Slice(unsafe.StringData(v), len(v))
+	case int64:
+		buf = strconv.AppendInt(nil, v, 10)
+	case float64:
+		buf = strconv.AppendFloat(nil, v, 'g', -1, 64)
+	case time.Time:
+		buf = append(buf, '"')
+		buf = v.AppendFormat(buf, time.RFC3339Nano)
+		buf = append(buf, '"')
+	case nil:
+		buf = append(buf, "null"...)
+	}
+
+	return j.UnmarshalJSON(buf)
+}

stmt.go

@@ -263,7 +263,7 @@ func (s *Stmt) BindJSON(param int, value any) error {
 	r := s.c.call(s.c.api.bindText,
 		uint64(s.handle), uint64(param),
 		uint64(ptr), uint64(len(data)),
-		uint64(s.c.api.destructor))
+		uint64(s.c.api.destructor), _UTF8)
 	return s.c.error(r)
 }
 

tests/json_test.go

@@ -0,0 +1,68 @@
+package tests
+
+import (
+	"encoding/json"
+	"math"
+	"testing"
+	"time"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/driver"
+	"github.com/ncruces/julianday"
+)
+
+func TestJSON(t *testing.T) {
+	t.Parallel()
+
+	db, err := driver.Open(":memory:", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec(`CREATE TABLE IF NOT EXISTS test (col)`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	reference := time.Date(2013, 10, 7, 4, 23, 19, 120_000_000, time.FixedZone("", -4*3600))
+
+	_, err = db.Exec(
+		`INSERT INTO test (col) VALUES (?), (?), (?), (?)`,
+		nil, 1, math.Pi, reference,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = db.Exec(
+		`INSERT INTO test (col) VALUES (?), (?), (?), (?)`,
+		sqlite3.JSON(math.Pi), sqlite3.JSON(false),
+		julianday.Format(reference), sqlite3.JSON([]string{}))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rows, err := db.Query("SELECT * FROM test")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := []string{
+		"null", "1", "3.141592653589793",
+		`"2013-10-07T04:23:19.12-04:00"`,
+		"3.141592653589793", "false",
+		"2456572.849526851851852", "[]",
+	}
+	for rows.Next() {
+		var got json.RawMessage
+		err = rows.Scan(sqlite3.JSON(&got))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if string(got) != want[0] {
+			t.Errorf("got %q, want %q", got, want[0])
+		}
+		want = want[1:]
+	}
+}

time.go

@@ -339,8 +339,9 @@ func (f TimeFormat) parseRelaxed(s string) (time.Time, error) {
 	return t, nil
 }
 
-// Scanner returns a [database/sql.Scanner] that
-// decodes a time value into dest using this format.
+// Scanner returns a [database/sql.Scanner] that can be used as an argument to
+// [database/sql.Row.Scan] and similar methods to
+// decode a time value into dest using this format.
 func (f TimeFormat) Scanner(dest *time.Time) interface{ Scan(any) error } {
 	return timeScanner{dest, f}
 }