key: deduplicate shadows while adding (#207)

file_test.go

@@ -305,3 +305,22 @@ func TestFile_SaveTo(t *testing.T) {
 		So(f.SaveToIndent("testdata/conf_out.ini", "\t"), ShouldBeNil)
 	})
 }
+
+// Inspired by https://github.com/go-ini/ini/issues/207
+func TestReloadAfterShadowLoad(t *testing.T) {
+	Convey("Reload file after ShadowLoad", t, func() {
+		f, err := ini.ShadowLoad([]byte(`
+[slice]
+v = 1
+v = 2
+v = 3
+`))
+		So(err, ShouldBeNil)
+		So(f, ShouldNotBeNil)
+
+		So(f.Section("slice").Key("v").ValueWithShadows(), ShouldResemble, []string{"1", "2", "3"})
+
+		So(f.Reload(), ShouldBeNil)
+		So(f.Section("slice").Key("v").ValueWithShadows(), ShouldResemble, []string{"1", "2", "3"})
+	})
+}

key.go

@@ -54,6 +54,16 @@ func (k *Key) addShadow(val string) error {
 		return errors.New("cannot add shadow to auto-increment or boolean key")
 	}
 
+	// Deduplicate shadows based on their values.
+	if k.value == val {
+		return nil
+	}
+	for i := range k.shadows {
+		if k.shadows[i].value == val {
+			return nil
+		}
+	}
+
 	shadow := newKey(k.s, k.name, val)
 	shadow.isShadow = true
 	k.shadows = append(k.shadows, shadow)