Messages are shared between the server (Java) and Themes.
Changes made to message files will be picked up by the Java code on build, but in order for them to be picked up by the Themes you need to run make build_languages.
For Themes an additional 'xx' locale is created which just shows the message id surrounded by '^' if an entry exists in the messages_en file, or '*' if no current en translation exists.
The presence of a label surrounded by '*' when using the 'xx' locale indicates that the message needs to be added to the src/messages/messages_en.properties file so that this can be picked up by Crowdin.
We can take advantage of existing Keycloak translations of any messages we use by running make refresh_messages.
Note that we explicitly list the messages that we use in our own messages_en rather than just using all existing Keycloak translations because Keycloak currently supports far fewer languages that Open Food Facts so we don't want to burden our Crowdin community with translating many messages that are never used.
The translations from Languages and Countries are obtained from the Open Food Facts taxonomies, rather than Crowdin. These taxonomy JSON files are cached in the build-scripts folder. The files are refreshed from Product Opener when make refresh_messages is run.
This list would always show each language in its own translation, e.g. "English, Français, 汉语".
The build_languages script reads the language.json and for each language uses the language_code_2 to look up the name. If no name is found in that language then the "en" translation will be used and if that cannot be found then the id of the entry will be used (with the "en:" prefix).
The basic list defined in runtime-scripts/user_profiles.json simply consist of placeholders for all the entries which will link to translations in a message file.
The build_languages script creates a message file for each known language and adds all countries to that.