The most important point is that automated validation supports human review rather than replacing it. A script can detect structure, placeholders, and restricted phrases, but only a knowledgeable reviewer can judge tone, cultural meaning, and emotional impact.
Checking for both missing and obsolete keys is a good approach. Most localization tools focus on missing content, but abandoned keys also create confusion for translators and make it harder to understand which copy is still used by the product.
I like the distinction between errors and warnings. Missing keys should block deployment, while long translations should trigger visual review rather than automatically fail. Different languages should not be forced into limits designed around English.
Placeholder validation is especially valuable. A translation can be valid JSON and still fail at runtime because {count} became {total}. Comparing placeholder sets in CI is a small check that can prevent surprisingly difficult production bugs.
happyday
日本文化をWebで身近にする個人開発者
A localization check is only useful if its report identifies the exact locale, key, and reason for failure. Clear CI output can turn translation validation from an annoying build error into something developers and editors can fix quickly.