types: support type aliases (#316)

* types: support type aliases

* chore: remove unused code

---------

Co-authored-by: Knut Olav Løite <koloite@gmail.com>

Author: tburgin

driver.go

@@ -1038,11 +1038,12 @@ func (c *conn) CheckNamedValue(value *driver.NamedValue) error {
 	if checkIsValidType(value.Value) {
 		return nil
 	}
-	if valuer, ok := value.Value.(driver.Valuer); ok {
-		v, err := callValuerValue(valuer)
-		if err != nil {
-			return err
-		}
+
+	// Convert the value using the default sql driver. This uses driver.Valuer,
+	// if implemented, and falls back to reflection. If the converted value is
+	// a supported spanner type, use it. Otherwise, ignore any errors and
+	// continue checking other supported spanner specific types.
+	if v, err := driver.DefaultParameterConverter.ConvertValue(value.Value); err == nil {
 		if checkIsValidType(v) {
 			value.Value = v
 			return nil
@@ -1252,27 +1253,6 @@ func (c *conn) createPartitionedDmlQueryOptions() spanner.QueryOptions {
 	return spanner.QueryOptions{ExcludeTxnFromChangeStreams: c.excludeTxnFromChangeStreams}
 }
 
-// callValuerValue is from Go's database/sql package to handle a special case,
-// in the same way that database/sql does, for nil pointers to types that implement
-// driver.Valuer with value receivers.
-
-var valuerReflectType = reflect.TypeOf((*driver.Valuer)(nil)).Elem()
-
-// callValuerValue returns vr.Value(), with one exception:
-// If vr.Value is a value receiver method on a pointer type and the pointer is nil,
-// it would panic at runtime. This treats it like nil instead.
-//
-// This is so people can implement driver.Value on value types and still use nil pointers
-// to those types to mean nil/NULL, just like the Go database/sql package.
-func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
-	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Ptr &&
-		rv.IsNil() &&
-		rv.Type().Elem().Implements(valuerReflectType) {
-		return nil, nil
-	}
-	return vr.Value()
-}
-
 /* The following is the same implementation as in google-cloud-go/spanner */
 
 func isStructOrArrayOfStructValue(v interface{}) bool {

driver_test.go

@@ -17,6 +17,7 @@ package spannerdriver
 import (
 	"context"
 	"database/sql/driver"
+	"net"
 	"testing"
 	"time"
 
@@ -494,6 +495,11 @@ func TestConn_CheckNamedValue(t *testing.T) {
 		{in: &Person{Name: "hello", Age: 123}, want: &Person{Name: "hello", Age: 123}},
 		// nil pointer of type that implements driver.Valuer via value receiver should use nil
 		{in: testNil, want: nil},
+		// net.IP reflects to []byte. Allow model structs to have fields with
+		// types that reflect to types supported by spanner.
+		{in: net.IPv6loopback, want: []byte(net.IPv6loopback)},
+		// Similarly, time.Duration is just an int64.
+		{in: time.Duration(1), want: int64(time.Duration(1))},
 	}
 
 	for _, test := range tests {

integration_test.go

@@ -24,6 +24,7 @@ import (
 	"math"
 	"math/big"
 	"math/rand"
+	"net"
 	"os"
 	"reflect"
 	"strconv"
@@ -505,6 +506,9 @@ func TestTypeRoundtrip(t *testing.T) {
 		// JSON variants
 		{in: spanner.NullJSON{Valid: true, Value: map[string]any{"a": 13}}, skipeq: true},
 		{in: []spanner.NullJSON{{Valid: true, Value: map[string]any{"a": 13}}}, skipeq: true},
+		// Standard library type alias examples
+		{in: net.IPv6loopback},
+		{in: time.Duration(1)},
 	}
 
 	for _, test := range tests {