[rejected AI] Fix i18n silently disabled when Flask-Babel isn't installed

[cristianchiriac]

Fixes #582.

Bug

Plain wtforms.Form works out of the box with meta={"locales": [...]}, no Flask-Babel needed:

form = wtforms.Form(flask.request.form, meta={"locales": ["fr"]})

But the same configuration on a FlaskForm silently produces English error messages unless Flask-Babel is installed and initialized:

form = FlaskForm(flask.request.form, meta={"locales": ["fr"]})

FlaskForm.Meta.get_translations() is the reason:

def get_translations(self, form):
    if not current_app.config.get("WTF_I18N_ENABLED", True):
        return super().get_translations(form)
    return translations

translations (imported from flask_wtf.i18n) is None whenever Flask-Babel isn't installed — caught as an ImportError in flask_wtf/form.py. With WTF_I18N_ENABLED at its default (True), this method returns that None unconditionally, discarding the form's own meta.locales-based translations entirely, instead of falling back to WTForms' own translation machinery the way the WTF_I18N_ENABLED=False branch already does.

Fix

Also fall back to super().get_translations(form) when translations is None.

Test plan

• Added test_i18n_falls_back_without_babel, monkeypatching flask_wtf.form.translations to None (deterministic regardless of whether Flask-Babel happens to be installed in the CI matrix) and asserting a meta.locales-configured form still gets localized errors.
• Verified the test fails with the exact reported behavior (English message instead of the Spanish one) against the unpatched code, and passes after the fix.
• Reproduced the issue's own example directly (French vs English) against both the unpatched and patched code, with and without Flask-Babel actually installed.
• pytest tests/ — 84 passed (up from 80), 2 skipped (unchanged) with Flask-Babel installed; ran the full suite both with and without Flask-Babel present.
• ruff check / ruff format --check — clean.
• Added a changelog entry per CONTRIBUTING.rst.

[davidism]

https://palletsprojects.com/contributing/llm-ai