Add support for NamedValueChecker interface

Added in 1.9: https://go.dev/doc/go1.9#minor_library_changes.

Close #640.

array.go

@@ -20,6 +20,7 @@ var typeSQLScanner = reflect.TypeOf((*sql.Scanner)(nil)).Elem()
 //
 // For example:
 //  db.Query(`SELECT * FROM t WHERE id = ANY($1)`, pq.Array([]int{235, 401}))
+//  db.Query(`SELECT * FROM t WHERE id = ANY($1)`, []int{235, 401}) // go1.9+
 //
 //  var x []sql.NullInt64
 //  db.QueryRow(`SELECT ARRAY[235, 401]`).Scan(pq.Array(&x))

conn_go19.go

@@ -0,0 +1,34 @@
+// +build go1.9
+
+package pq
+
+import (
+	"database/sql/driver"
+	"reflect"
+)
+
+var _ driver.NamedValueChecker = (*conn)(nil)
+
+func (c *conn) CheckNamedValue(nv *driver.NamedValue) error {
+	if _, ok := nv.Value.(driver.Valuer); ok {
+		// Ignore Valuer, for backward compatiblity with pq.Array()
+		return driver.ErrSkip
+	}
+
+	// Ignoring []byte / []uint8
+	if _, ok := nv.Value.([]uint8); ok {
+		return driver.ErrSkip
+	}
+
+	v := reflect.ValueOf(nv.Value)
+	if v.Kind() == reflect.Ptr {
+		v = v.Elem()
+	}
+	if v.Kind() == reflect.Slice {
+		var err error
+		nv.Value, err = Array(nv.Value).Value()
+		return err
+	}
+
+	return driver.ErrSkip
+}

conn_go19_test.go

@@ -0,0 +1,65 @@
+// +build go1.9
+
+package pq
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestArrayArg(t *testing.T) {
+	db := openTestConn(t)
+	defer db.Close()
+
+	for _, tc := range []struct {
+		name string
+		want interface{}
+	}{
+		{
+			name: "slice-value",
+			want: []int64{245, 231},
+		},
+		{
+			name: "slice-pointer",
+			want: &[]int64{245, 231},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			r, err := db.Query("SELECT $1::int[]", tc.want)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer r.Close()
+
+			if !r.Next() {
+				if r.Err() != nil {
+					t.Fatal(r.Err())
+				}
+				t.Fatal("expected row")
+			}
+
+			defer func() {
+				if r.Next() {
+					t.Fatal("unexpected row")
+				}
+			}()
+
+			rt := reflect.TypeOf(tc.want)
+			got := reflect.New(rt)
+			{
+				got := got
+				if rt.Kind() == reflect.Ptr {
+					got = got.Elem()
+				}
+				if err := r.Scan(Array(got.Interface())); err != nil {
+					t.Fatal(err)
+				}
+			}
+
+			if !reflect.DeepEqual(tc.want, got.Interface()) {
+				t.Errorf("got %v, want %v", got, tc.want)
+			}
+		})
+	}
+
+}