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114 lines
6.0 KiB
Markdown
114 lines
6.0 KiB
Markdown
# Internationalization
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> Supporting internationalization is not optional. It must be a core feature.
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>
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> — [Jannis Leidel, speaking at Django Under the Hood, 2015][cite].
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REST framework ships with translatable error messages. You can make these appear in your language enabling [Django's standard translation mechanisms][django-translation].
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Doing so will allow you to:
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* Select a language other than English as the default, using the standard `LANGUAGE_CODE` Django setting.
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* Allow clients to choose a language themselves, using the `LocaleMiddleware` included with Django. A typical usage for API clients would be to include an `Accept-Language` request header.
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## Enabling internationalized APIs
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You can change the default language by using the standard Django `LANGUAGE_CODE` setting:
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LANGUAGE_CODE = "es-es"
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You can turn on per-request language requests by adding `LocalMiddleware` to your `MIDDLEWARE_CLASSES` setting:
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MIDDLEWARE_CLASSES = [
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...
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'django.middleware.locale.LocaleMiddleware'
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]
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When per-request internationalization is enabled, client requests will respect the `Accept-Language` header where possible. For example, let's make a request for an unsupported media type:
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**Request**
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GET /api/users HTTP/1.1
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Accept: application/xml
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Accept-Language: es-es
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Host: example.org
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**Response**
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HTTP/1.0 406 NOT ACCEPTABLE
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{"detail": "No se ha podido satisfacer la solicitud de cabecera de Accept."}
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REST framework includes these built-in translations both for standard exception cases, and for serializer validation errors.
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Note that the translations only apply to the error strings themselves. The format of error messages, and the keys of field names will remain the same. An example `400 Bad Request` response body might look like this:
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{"detail": {"username": ["Esse campo deve ser unico."]}}
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If you want to use different string for parts of the response such as `detail` and `non_field_errors` then you can modify this behavior by using a [custom exception handler][custom-exception-handler].
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#### Specifying the set of supported languages.
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By default all available languages will be supported.
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If you only wish to support a subset of the available languages, use Django's standard `LANGUAGES` setting:
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LANGUAGES = [
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('de', _('German')),
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('en', _('English')),
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]
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## Adding new translations
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REST framework translations are managed online using [Transifex][transifex-project]. You can use the Transifex service to add new translation languages. The maintenance team will then ensure that these translation strings are included in the REST framework package.
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Sometimes you may need to add translation strings to your project locally. You may need to do this if:
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* You want to use REST Framework in a language which has not been translated yet on Transifex.
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* Your project includes custom error messages, which are not part of REST framework's default translation strings.
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#### Translating a new language locally
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This guide assumes you are already familiar with how to translate a Django app. If you're not, start by reading [Django's translation docs][django-translation].
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If you're translating a new language you'll need to translate the existing REST framework error messages:
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1. Make a new folder where you want to store the internationalization resources. Add this path to your [`LOCALE_PATHS`][django-locale-paths] setting.
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2. Now create a subfolder for the language you want to translate. The folder should be named using [locale name][django-locale-name] notation. For example: `de`, `pt_BR`, `es_AR`.
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3. Now copy the [base translations file][django-po-source] from the REST framework source code into your translations folder.
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4. Edit the `django.po` file you've just copied, translating all the error messages.
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5. Run `manage.py compilemessages -l pt_BR` to make the translations
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available for Django to use. You should see a message like `processing file django.po in <...>/locale/pt_BR/LC_MESSAGES`.
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6. Restart your development server to see the changes take effect.
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If you're only translating custom error messages that exist inside your project codebase you don't need to copy the REST framework source `django.po` file into a `LOCALE_PATHS` folder, and can instead simply run Django's standard `makemessages` process.
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## How the language is determined
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If you want to allow per-request language preferences you'll need to include `django.middleware.locale.LocaleMiddleware` in your `MIDDLEWARE_CLASSES` setting.
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You can find more information on how the language preference is determined in the [Django documentation][django-language-preference]. For reference, the method is:
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1. First, it looks for the language prefix in the requested URL.
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2. Failing that, it looks for the `LANGUAGE_SESSION_KEY` key in the current user’s session.
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3. Failing that, it looks for a cookie.
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4. Failing that, it looks at the `Accept-Language` HTTP header.
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5. Failing that, it uses the global `LANGUAGE_CODE` setting.
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For API clients the most appropriate of these will typically be to use the `Accept-Language` header; Sessions and cookies will not be available unless using session authentication, and generally better practice to prefer an `Accept-Language` header for API clients rather than using language URL prefixes.
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[cite]: http://youtu.be/Wa0VfS2q94Y
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[django-translation]: https://docs.djangoproject.com/en/1.7/topics/i18n/translation
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[custom-exception-handler]: ../api-guide/exceptions.md#custom-exception-handling
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[transifex-project]: https://www.transifex.com/projects/p/django-rest-framework/
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[django-po-source]: https://raw.githubusercontent.com/tomchristie/django-rest-framework/master/rest_framework/locale/en_US/LC_MESSAGES/django.po
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[django-language-preference]: https://docs.djangoproject.com/en/1.7/topics/i18n/translation/#how-django-discovers-language-preference
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[django-locale-paths]: https://docs.djangoproject.com/en/1.7/ref/settings/#std:setting-LOCALE_PATHS
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[django-locale-name]: https://docs.djangoproject.com/en/1.7/topics/i18n/#term-locale-name
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[contributing]: ../../CONTRIBUTING.md
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