Performing localization of menulist using addon sdk - localization

Question

Have a menulist preference in my addon and I'm trying to localize it.
The preference works fine from a functional point of view but when I change my browser's locale to es-ES, I still see the English translations.
Is there a declaration error here?
The official documentation does not give full examples of it's usage.
https://addons.mozilla.org/en-US/developers/docs/sdk/latest/dev-guide/tutorials/l10n.html
package.json:
{
"name": "extensions.savetexttofile.saveMode",
"title": "Save mode?",
"type": "menulist",
"value": 0,
"options": [
{
"value": "0",
"label": "Create new file"
},
{
"value": "1",
"label": "Append to existing file"
}
]
}]
tail -n 4 locale/es-ES.properties:
extensions.savetexttofile.saveMode_title= modo de ahorro de?
extensions.savetexttofile.saveMode_description= Método para guardar texto:
extensions.savetexttofile.saveMode_options.0= Crear un archivo nuevo
extensions.savetexttofile.saveMode_options.1= Añadir a un archivo existente

Answer 1

For options, you must use the label of the option in your properties file, like so (tested):
extensions.savetexttofile.saveMode_title= modo de ahorro de?
extensions.savetexttofile.saveMode_description= Método para guardar texto:
extensions.savetexttofile.saveMode_options.Create new file= Crear un archivo nuevo
extensions.savetexttofile.saveMode_options.Append to existing file= Añadir a un archivo existente
This looks kinda nasty, so it might be advisable to use a "generic" name in your package.json like createand append and localize that as saveMode_options.create= in all locales, including your en-US.properties.
On an unrelated note: It is not necessary to prefix your SDK prefs with extensions.savetexttofile.. The add-on SDK already prefixes it with your add-on id, so that you end up with a double prefix like extensions.jid1-pL3SKrUpOJo04Q#jetpack.extensions.savetexttofile.saveMode)