provide reflectx.FieldByIndexesReadOnly which does not allocate nil p…

…ointers, which fixes two bugs with named queries: the first is unaddressable values passed to Named exec/query/etc that had nil pointers attempted an illegal set and paniced, and the second is described in jmoiron#68

named.go

@@ -154,7 +154,7 @@ func bindArgs(names []string, arg interface{}) ([]interface{}, error) {
 		if len(t) == 0 {
 			return arglist, fmt.Errorf("could not find name %s in %v", names[i], arg)
 		}
-		val := reflectx.FieldByIndexes(v, t)
+		val := reflectx.FieldByIndexesReadOnly(v, t)
 		arglist = append(arglist, val.Interface())
 	}
 

reflectx/reflect.go

@@ -139,6 +139,16 @@ func FieldByIndexes(v reflect.Value, indexes []int) reflect.Value {
 	return v
 }
 
+// FieldByIndexesReadOnly returns a value for a particular struct traversal,
+// but is not concerned with allocating nil pointers because the value is
+// going to be used for reading and not setting.
+func FieldByIndexesReadOnly(v reflect.Value, indexes []int) reflect.Value {
+	for _, i := range indexes {
+		v = reflect.Indirect(v).Field(i)
+	}
+	return v
+}
+
 // Deref is Indirect for reflect.Types
 func Deref(t reflect.Type) reflect.Type {
 	if t.Kind() == reflect.Ptr {

sqlx_test.go

@@ -504,6 +504,51 @@ func TestNamedQuery(t *testing.T) {
 	})
 }
 
+func TestNilInserts(t *testing.T) {
+	var schema = Schema{
+		create: `
+			CREATE TABLE tt (
+				id integer,
+				value text NULL DEFAULT NULL
+			);`,
+		drop: "drop table tt;",
+	}
+
+	RunWithSchema(schema, t, func(db *DB, t *testing.T) {
+		type TT struct {
+			Id    int
+			Value *string
+		}
+		var v, v2 TT
+		r := db.Rebind
+
+		db.MustExec(r(`INSERT INTO tt (id) VALUES (1)`))
+		db.Get(&v, r(`SELECT * FROM tt`))
+		if v.Id != 1 {
+			t.Errorf("Expecting id of 1, got %v", v.Id)
+		}
+		if v.Value != nil {
+			t.Errorf("Expecting NULL to map to nil, got %s", v.Value)
+		}
+
+		v.Id = 2
+		// NOTE: this incidentally uncovered a bug which was that named queries with
+		// pointer destinations would not work if the passed value here was not addressable,
+		// as reflectx.FieldByIndexes attempts to allocate nil pointer receivers for
+		// writing.  This was fixed by creating & using the reflectx.FieldByIndexesReadOnly
+		// function.  This next line is important as it provides the only coverage for this.
+		db.NamedExec(`INSERT INTO tt (id, value) VALUES (:id, :value)`, v)
+
+		db.Get(&v2, r(`SELECT * FROM tt WHERE id=2`))
+		if v.Id != v2.Id {
+			t.Errorf("%v != %v", v.Id, v2.Id)
+		}
+		if v2.Value != nil {
+			t.Errorf("Expecting NULL to map to nil, got %s", v.Value)
+		}
+	})
+}
+
 func TestScanError(t *testing.T) {
 	var schema = Schema{
 		create: `