@lingui/cli/dist/api/catalog/mergeCatalog.js

Lingui CLI to extract messages, compile catalogs, and manage translation workflows

export function mergeCatalog(prevCatalog, nextCatalog, forSourceLocale, options) {
    prevCatalog = prevCatalog || {};
    const nextKeys = Object.keys(nextCatalog);
    const prevKeys = Object.keys(prevCatalog);
    // this part is optimized for performance, see https://github.com/lingui/js-lingui/pull/2540
    const hasKeysInBothCatalogs = prevKeys.length > 0 && nextKeys.length > 0;
    let newKeys;
    let mergeKeys;
    let obsoleteKeys;
    if (hasKeysInBothCatalogs) {
        const prevKeySet = new Set(prevKeys);
        const nextKeySet = new Set(nextKeys);
        newKeys = nextKeys.filter((key) => !prevKeySet.has(key));
        mergeKeys = nextKeys.filter((key) => prevKeySet.has(key));
        obsoleteKeys = prevKeys.filter((key) => !nextKeySet.has(key));
    }
    else {
        newKeys = nextKeys;
        mergeKeys = [];
        obsoleteKeys = prevKeys;
    }
    // Initialize new catalog with new keys
    const newMessages = Object.fromEntries(newKeys.map((key) => [
        key,
        {
            translation: forSourceLocale ? nextCatalog[key].message || key : "",
            ...nextCatalog[key],
        },
    ]));
    // Merge translations from previous catalog
    const mergedMessages = Object.fromEntries(mergeKeys.map((key) => {
        const updateFromDefaults = forSourceLocale &&
            (prevCatalog[key].translation === prevCatalog[key].message ||
                options.overwrite);
        const translation = updateFromDefaults
            ? nextCatalog[key].message || key
            : prevCatalog[key].translation;
        const { extra } = prevCatalog[key];
        return [key, { ...nextCatalog[key], extra, translation }];
    }));
    // Mark all remaining translations as obsolete
    // Only if *options.files* is not provided
    const obsoleteMessages = Object.fromEntries(obsoleteKeys.map((key) => [
        key,
        {
            ...prevCatalog[key],
            ...(options.files ? {} : { obsolete: true }),
        },
    ]));
    return { ...newMessages, ...mergedMessages, ...obsoleteMessages };
}