Sergey Vanyushkin
d32ad29abc
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Add i18n support to the blog web UI with 4 languages (en/ru/fr/de),
80 translation keys, automatic Accept-Language detection, persistent
locale cookie, and a language switcher dropdown in the header.
- Infrastructure: TranslationService, translation dicts, convenience _()
- Presentation: locale middleware, /web/lang/{locale} switcher route
- Templates: all 9 templates use {{ _(key, current_locale) }}
- Tests: 26 tests across TranslationService, locale detection helpers
- Docs: TEST_MODEL.md and FEATURE_INFRASTRUCTURE.md updated with TC-UNIT-811-821
73 lines
2.0 KiB
Python
73 lines
2.0 KiB
Python
"""Locale detection and management for i18n support.
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This module provides locale detection from Accept-Language headers and cookies,
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following the same middleware pattern as the flash message system.
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"""
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from fastapi import Request
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from app.infrastructure.i18n.translator import DEFAULT_LOCALE, SUPPORTED_LOCALES
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LOCALE_COOKIE_NAME = "locale"
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SUPPORTED_LOCALES_SET: frozenset[str] = SUPPORTED_LOCALES
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def _parse_accept_language(header: str) -> list[str]:
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"""Parse Accept-Language header into ordered list of locale codes.
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Args:
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header: Raw Accept-Language header value.
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Returns:
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List of locale codes in preference order, with region subtags removed.
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"""
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if not header:
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return []
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locales: list[str] = []
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for part in header.split(","):
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part = part.strip()
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if not part:
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continue
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locale = part.split(";")[0].strip().split("-")[0]
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if locale:
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locales.append(locale)
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return locales
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def _get_best_locale(request: Request) -> str:
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"""Detect the best locale for the current request.
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Priority order: cookie → Accept-Language header → default.
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Args:
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request: FastAPI request object.
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Returns:
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Best matching locale code, defaulting to ``en``.
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"""
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cookie_locale = request.cookies.get(LOCALE_COOKIE_NAME)
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if cookie_locale and cookie_locale in SUPPORTED_LOCALES_SET:
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return cookie_locale
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accept_language = request.headers.get("accept-language", "")
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for lang in _parse_accept_language(accept_language):
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if lang in SUPPORTED_LOCALES_SET:
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return lang
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return DEFAULT_LOCALE
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async def setup_locale_manager(request: Request) -> None:
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"""Set the detected locale on request state.
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Called early in the request lifecycle so that route handlers and
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template rendering can access the current locale via
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``request.state.locale``.
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Args:
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request: FastAPI request object.
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"""
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if not hasattr(request.state, "locale"):
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request.state.locale = _get_best_locale(request)
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