fix: Columns and Values should recognize pointer values too (#67)

Author: taronish-stytch

columns.go

@@ -121,7 +121,7 @@ func columnNames(model reflect.Value, strict bool, excluded ...string) []string
 			continue
 		}
 
-		if supportedColumnType(valField.Kind()) || isValidSqlValue(valField) {
+		if supportedColumnType(valField) || isValidSqlValue(valField) {
 			names = append(names, fieldName)
 		}
 	}
@@ -152,13 +152,16 @@ func reflectValue(v interface{}) (reflect.Value, error) {
 	return vVal, nil
 }
 
-func supportedColumnType(k reflect.Kind) bool {
-	switch k {
+func supportedColumnType(v reflect.Value) bool {
+	switch v.Kind() {
 	case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
 		reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
 		reflect.Uint64, reflect.Float32, reflect.Float64, reflect.Interface,
 		reflect.String:
 		return true
+	case reflect.Ptr:
+		ptrVal := reflect.New(v.Type().Elem())
+		return supportedColumnType(ptrVal.Elem())
 	default:
 		return false
 	}
@@ -169,6 +172,11 @@ func isValidSqlValue(v reflect.Value) bool {
 	// 1. It returns true for sql.driver's type check for types like time.Time
 	// 2. It implements the driver.Valuer interface allowing conversion directly
 	//    into sql statements
+	if v.Kind() == reflect.Ptr {
+		ptrVal := reflect.New(v.Type().Elem())
+		return isValidSqlValue(ptrVal.Elem())
+	}
+
 	if driver.IsValue(v.Interface()) {
 		return true
 	}

columns_test.go

@@ -272,7 +272,17 @@ func TestColumnsStoresOneCacheEntryPerInstance(t *testing.T) {
 	assert.Equal(t, 1, after-before, "Cache size grew unexpectedly")
 }
 
-func TestValuesWorkWithValidSqlValueTypes(t *testing.T) {
+func TestColumnsReturnsStructTagsWithPointers(t *testing.T) {
+	type personUpdate struct {
+		Name *string `db:"name"`
+	}
+
+	cols, err := Columns(&personUpdate{})
+	assert.NoError(t, err)
+	assert.EqualValues(t, []string{"name"}, cols)
+}
+
+func TestColumnsWorkWithValidSqlValueTypes(t *testing.T) {
 	type coupon struct {
 		Value   int       `db:"value"`
 		Expires time.Time `db:"expires"`
@@ -284,6 +294,18 @@ func TestValuesWorkWithValidSqlValueTypes(t *testing.T) {
 	assert.EqualValues(t, []string{"value", "expires"}, cols)
 }
 
+func TestColumnsWorkWithPointerValidSqlTypes(t *testing.T) {
+	type coupon struct {
+		Value   int        `db:"value"`
+		Expires *time.Time `db:"expires"`
+	}
+
+	c := &coupon{}
+	cols, err := Columns(c)
+	assert.NoError(t, err)
+	assert.EqualValues(t, []string{"value", "expires"}, cols)
+}
+
 type Pet struct {
 	Species string
 	Name    string
@@ -310,3 +332,7 @@ func BenchmarkColumnsLargeStruct(b *testing.B) {
 		Columns(ls)
 	}
 }
+
+func ptr(s string) *string {
+	return &s
+}

example_scanner_test.go

@@ -33,6 +33,7 @@ func exampleDB() *sql.DB {
 	);`,
 		`INSERT INTO person (id, name) VALUES (1, 'brett', 1);`,
 		`INSERT INTO person (id, name) VALUES (2, 'fred', 1);`,
+		`INSERT INTO person (id) VALUES (3);`,
 	)
 }
 
@@ -136,6 +137,53 @@ func ExampleRowStrict() {
 	// {"ID":0,"Name":"brett"}
 }
 
+func ExampleRowPtr() {
+	db := exampleDB()
+	defer db.Close()
+	rows, err := db.Query("SELECT id,name FROM person where id = 3 LIMIT 1")
+	if err != nil {
+		panic(err)
+	}
+
+	var person struct {
+		ID   int
+		Name *string `db:"name"`
+	}
+
+	err = scan.RowStrict(&person, rows)
+	if err != nil {
+		panic(err)
+	}
+
+	json.NewEncoder(os.Stdout).Encode(&person)
+	// Output:
+	// {"ID":0,"Name":null}
+}
+
+func ExampleRowPtrType() {
+	db := exampleDB()
+	defer db.Close()
+	rows, err := db.Query("SELECT id,name FROM person where id = 3 LIMIT 1")
+	if err != nil {
+		panic(err)
+	}
+
+	type NullableString *string
+	var person struct {
+		ID   int
+		Name NullableString `db:"name"`
+	}
+
+	err = scan.RowStrict(&person, rows)
+	if err != nil {
+		panic(err)
+	}
+
+	json.NewEncoder(os.Stdout).Encode(&person)
+	// Output:
+	// {"ID":0,"Name":null}
+}
+
 func ExampleRow_scalar() {
 	db := exampleDB()
 	defer db.Close()
@@ -165,8 +213,8 @@ func ExampleRows() {
 	}
 
 	var persons []struct {
-		ID   int    `db:"id"`
-		Name string `db:"name"`
+		ID   int     `db:"id"`
+		Name *string `db:"name"`
 	}
 
 	err = scan.Rows(&persons, rows)
@@ -176,7 +224,7 @@ func ExampleRows() {
 
 	json.NewEncoder(os.Stdout).Encode(&persons)
 	// Output:
-	// [{"ID":1,"Name":"brett"},{"ID":2,"Name":"fred"}]
+	// [{"ID":1,"Name":"brett"},{"ID":2,"Name":"fred"},{"ID":3,"Name":null}]
 }
 
 func ExampleRowsStrict() {
@@ -189,7 +237,7 @@ func ExampleRowsStrict() {
 
 	var persons []struct {
 		ID   int
-		Name string `db:"name"`
+		Name *string `db:"name"`
 	}
 
 	err = scan.Rows(&persons, rows)
@@ -199,13 +247,13 @@ func ExampleRowsStrict() {
 
 	json.NewEncoder(os.Stdout).Encode(&persons)
 	// Output:
-	// [{"ID":0,"Name":"brett"},{"ID":0,"Name":"fred"}]
+	// [{"ID":0,"Name":"brett"},{"ID":0,"Name":"fred"},{"ID":0,"Name":null}]
 }
 
 func ExampleRows_primitive() {
 	db := exampleDB()
 	defer db.Close()
-	rows, err := db.Query("SELECT name FROM person ORDER BY id ASC")
+	rows, err := db.Query("SELECT name FROM person WHERE name IS NOT NULL ORDER BY id ASC")
 	if err != nil {
 		panic(err)
 	}

values_test.go

@@ -34,6 +34,30 @@ func TestValuesScansDBTags(t *testing.T) {
 	assert.EqualValues(t, []interface{}{"Brett"}, vals)
 }
 
+func TestValuesScansPointerDBTags(t *testing.T) {
+	type person struct {
+		Name *string `db:"n"`
+	}
+
+	p := &person{Name: ptr("Brett")}
+	vals, err := Values([]string{"n"}, p)
+	require.NoError(t, err)
+
+	assert.EqualValues(t, []interface{}{ptr("Brett")}, vals)
+}
+
+func TestValuesReturnsNilPointers(t *testing.T) {
+	type person struct {
+		Name *string `db:"n"`
+	}
+
+	p := &person{Name: nil}
+	vals, err := Values([]string{"n"}, p)
+	require.NoError(t, err)
+
+	assert.EqualValues(t, []interface{}{(*string)(nil)}, vals)
+}
+
 func TestValuesScansNestedFields(t *testing.T) {
 	type Address struct {
 		Street string
@@ -124,6 +148,22 @@ func TestValuesValidSqlTypes(t *testing.T) {
 	assert.EqualValues(t, []interface{}{25, tNow}, vals)
 }
 
+func TestValuesValidPointerSqlTypes(t *testing.T) {
+	tNow := time.Now()
+	type coupon struct {
+		Value   int
+		Expires *time.Time
+	}
+	c := &coupon{
+		Value:   25,
+		Expires: &tNow,
+	}
+
+	vals, err := Values([]string{"Value", "Expires"}, c)
+	require.NoError(t, err)
+	assert.EqualValues(t, []interface{}{25, &tNow}, vals)
+}
+
 func TestValuesDriverValuerImplementers(t *testing.T) {
 	type person struct {
 		Name string `db:"name"`