things seem to work

scripts/flatten-messages.js

@@ -0,0 +1,29 @@
+// Flattens messages extracted via the React Intl Babel plugin. An error will be
+// thrown if there are messages with the same `id`. The result is a file containing
+// `id: message` pairs in "en" locale.
+
+var fs = require('fs');
+var path = require('path');
+var globSync = require('glob').sync;
+var mkdirpSync = require('mkdirp').sync;
+
+const MESSAGES_PATTERN = './src/i18n/src/**/*.json';
+const LANG_DIR         = './src/i18n/';
+
+let messages = globSync(MESSAGES_PATTERN)
+  .map((filename) => fs.readFileSync(filename, 'utf8'))
+  .map((file) => JSON.parse(file))
+  .reduce((collection, descriptors) => {
+    descriptors.forEach(({id, defaultMessage}) => {
+      if (collection.hasOwnProperty(id)) {
+          throw new Error(`Duplicate message id: ${id}`);
+      }
+      collection[id] = defaultMessage;
+    });
+
+    return collection;
+  }, {});
+
+let filename = path.join(LANG_DIR, 'en.json');
+mkdirpSync(path.dirname(filename));
+fs.writeFileSync(filename, JSON.stringify(messages, null, 2));