Add MODELTRANS_DEFAULT_LANGUAGE setting (#117)

fixes: #116

docs/pages/inner-workings.rst

@@ -76,7 +76,7 @@ language is defined::
     # 'Valk', None
 
 The virtual field ``<field>_i18n`` returns the translated value for the current
-active language and falls back to the language in ``LANGUAGE_CODE``::
+active language and falls back to the language in ``MODELTRANS_DEFAULT_LANGUAGE``::
 
     with override("nl"):
         print(b.title_i18n)
@@ -88,7 +88,7 @@ active language and falls back to the language in ``LANGUAGE_CODE``::
 
     with override("fr"):
         print(b.title_i18n)
-    # 'Falcon' (no french translation available, falls back to LANGUAGE_CODE)
+    # 'Falcon' (no french translation available, falls back to MODELTRANS_DEFAULT_LANGUAGE)
 
 Django-modeltrans also allows ordering on translated values. Ordering on
 ``<field>_i18n`` probably makes most sense, as it more likely that there is a

docs/pages/settings.rst

@@ -4,14 +4,25 @@ Settings Reference
 django-modeltrans allows some configuration to define its behavior.
 By default, it tries to use sensible defaults derived from the default django settings.
 
+
+``MODELTRANS_DEFAULT_LANGUAGE``
+----------------------------------
+A string representing the default language.  By default, the default language is set to
+django's `LANGUAGE_CODE setting <https://docs.djangoproject.com/en/stable/ref/settings/#language-code>`_.
+
+Customize this setting to change the default language used by django-modeltrans without impacting
+Django's translation / locale middlewares.
+
+See `#116 <https://github.com/zostera/django-modeltrans/issues/116>`_ for additional context.
+
+
 ``MODELTRANS_AVAILABLE_LANGUAGES``
 ----------------------------------
 A list of language codes to allow model fields to be translated in. By default,
 the language codes extracted from django's `LANGUAGES setting <https://docs.djangoproject.com/en/stable/ref/settings/#languages>`_.
 
 Note that
- - the default language, defined in django's `LANGUAGE_CODE setting <https://docs.djangoproject.com/en/stable/ref/settings/#language-code>`_,
-   should not be added to this list (will be ignored).
+ - the default language, defined in `MODELTRANS_DEFAULT_LANGUAGE` should not be added to this list (will be ignored).
  - order is not important
 
 A custom definition might be::
@@ -23,18 +34,18 @@ A custom definition might be::
 
 ``MODELTRANS_FALLBACK``
 -----------------------
-A dict of fallback chains as lists of languages. By default, it falls back to the language defined in django setting `LANGUAGE_CODE`.
+A dict of fallback chains as lists of languages. By default, it falls back to the language defined in `MODELTRANS_DEFAULT_LANGUAGE`.
 
 For example, django-modeltrans will fall back to:
  - english when the active language is 'nl'
  - fist dutch and finally english with active language is 'fy'
 
 If configured like this::
 
-    LANGUAGE_CODE = 'en'
+    MODELTRANS_DEFAULT_LANGUAGE = 'en'
     MODELTRANS_AVAILABLE_LANGUAGES = ('nl', 'fy')
     MODELTRANS_FALLBACK = {
-       'default': (LANGUAGE_CODE, ),
+       'default': (MODELTRANS_DEFAULT_LANGUAGE, ),
        'fy': ('nl', 'en')
     }
 

docs/pages/working-with-models.rst

@@ -7,7 +7,7 @@ Custom fallback language
 ------------------------
 
 By default, fallback is centrally configured with :ref:`settings_fallback`.
-That might not be sufficient, for example if part of the content is created for a single language which is not ``LANGUAGE_CODE``.
+That might not be sufficient, for example if part of the content is created for a single language which is not ``MODELTRANS_DEFAULT_LANGUAGE``.
 
 In that case, it can be configured per-record using the ``fallback_language_field`` argument to ``TranslationField``::
 
@@ -27,7 +27,7 @@ You can traverse foreign key relations too::
 
 Note that
  - if in this example no `newsroom` is set yet, the centrally configured fallback is used.
- - the original field _always_ contains the language as configured by ``LANGUAGE_CODE``.
+ - the original field _always_ contains the language as configured by ``MODELTRANS_DEFAULT_LANGUAGE``.
 
 With the models above::
 

docs/spelling_wordlist.txt

@@ -12,6 +12,7 @@ ForeignKey
 fy
 german
 mixin
+middlewares
 modeltrans
 modeltranslation
 nl

modeltrans/conf.py

@@ -11,12 +11,13 @@ def get_modeltrans_setting(key):
             settings, "MODELTRANS_FALLBACK", {"default": (get_default_language(),)}
         ),
         "MODELTRANS_ADD_FIELD_HELP_TEXT": getattr(settings, "MODELTRANS_ADD_FIELD_HELP_TEXT", True),
+        "MODELTRANS_DEFAULT_LANGUAGE": get_default_language(),
     }
     return modeltrans_settings.get(key)
 
 
 def get_default_language():
-    return settings.LANGUAGE_CODE
+    return getattr(settings, "MODELTRANS_DEFAULT_LANGUAGE", getattr(settings, "LANGUAGE_CODE"))
 
 
 def get_available_languages_setting():

tests/test_conf.py

@@ -2,6 +2,9 @@
 from django.test import TestCase, override_settings
 
 from modeltrans.conf import check_fallback_chain, get_available_languages_setting
+from modeltrans.translator import check_languages, get_i18n_field, get_i18n_field_param
+
+from .app.models import Person
 
 
 class FallbackConfTest(TestCase):
@@ -37,3 +40,23 @@ def test_available_languages_should_be_str(self):
         message = "MODELTRANS_AVAILABLE_LANGUAGES should be an iterable of strings"
         with self.assertRaisesMessage(ImproperlyConfigured, message):
             get_available_languages_setting()
+
+
+class DefaultLanguageConfTest(TestCase):
+    @override_settings(LANGUAGE_CODE="es", MODELTRANS_AVAILABLE_LANGUAGES=("nl", "de", "fr"))
+    def test_django_language_code_not_available_language(self):
+        message = 'Language "en" is in required_languages on Model "Person" but not in settings.MODELTRANS_AVAILABLE_LANGUAGES.'
+        i18n_field = get_i18n_field(Person)
+        required_languages = get_i18n_field_param(Person, i18n_field, "required_languages")
+        with self.assertRaisesMessage(ImproperlyConfigured, message):
+            check_languages(required_languages, Person)
+
+    @override_settings(
+        LANGUAGE_CODE="es",
+        MODELTRANS_DEFAULT_LANGUAGE="en",
+        MODELTRANS_AVAILABLE_LANGUAGES=("nl", "de", "fr"),
+    )
+    def test_default_language_code_is_available_language(self):
+        i18n_field = get_i18n_field(Person)
+        required_languages = get_i18n_field_param(Person, i18n_field, "required_languages")
+        check_languages(required_languages, Person)