The files in this directory are based on ../lib/stock_strings.dart which defines all of the localizable strings used by the stocks app. The stocks app uses the Dart intl package.
Rebuilding everything requires two steps.
With the examples/stocks as the current directory, generate intl_messages.arb from lib/stock_strings.dart:
flutter pub pub run intl_translation:extract_to_arb --output-dir=lib/i18n lib/stock_strings.dart
The intl_messages.arb file is a JSON format map with one entry for each Intl.message() function defined in stock_strings.dart. This file was used to create the English and Spanish localizations, stocks_en.arb and stocks_es.arb. The intl_messages.arb wasn't checked into the repository, since it only serves as a template for the other .arb files.
With the examples/stocks as the current directory, generate a stock_messages_<locale>.dart for each stocks_<locale>.arb file and stock_messages_all.dart, which imports all of the messages files:
flutter pub pub run intl_translation:generate_from_arb --output-dir=lib/i18n \ --generated-file-prefix=stock_ --no-use-deferred-loading lib/*.dart lib/i18n/stocks_*.arb
The StockStrings class uses the generated initializeMessages() function (stock_messages_all.dart) to load the localized messages and Intl.message() to look them up.