Function translate

packages/localize/src/utils/src/translations.ts:55–87

(
  translations: Record<string, ParsedTranslation>,
  messageParts: TemplateStringsArray,
  substitutions: readonly unknown[],
)

 * error is thrown.
 */
export function translate(
  translations: Record<string, ParsedTranslation>,
  messageParts: TemplateStringsArray,
  substitutions: readonly unknown[],
): [TemplateStringsArray, readonly unknown[]] {
  const message = parseMessage(messageParts, substitutions);
  // Look up the translation using the messageId, and then the legacyId if available.
  let translation = translations[message.id];
  // If the messageId did not match a translation, try matching the legacy ids instead
  if (message.legacyIds !== undefined) {
    for (let i = 0; i < message.legacyIds.length && translation === undefined; i++) {
      translation = translations[message.legacyIds[i]];
    }
  }
  if (translation === undefined) {
    throw new MissingTranslationError(message);
  }
  return [
    translation.messageParts,
    translation.placeholderNames.map((placeholder) => {
      if (Object.hasOwn(message.substitutions, placeholder)) {
        return message.substitutions[placeholder];
      } else {
        throw new Error(
          `There is a placeholder name mismatch with the translation provided for the message ${describeMessage(
            message,
          )}.\n` +
            `The translation contains a placeholder with name ${placeholder}, which does not exist in the message.`,
        );
      }
    }),
  ];
}

/**
 * Parse the `messageParts` and `placeholderNames` out of a target `message`.