Delayed the reading of settings.USE_I18N until the first use of the i18n

functions. This solves a few import problems we are seeing. Fixed #3687. Refs #2920.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@4905 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/utils/translation/__init__.py

@@ -1,8 +1,94 @@
-from django.conf import settings
+"""
+Internationalization support.
+"""
+from django.utils.functional import lazy
 
-if settings.USE_I18N:
-    from trans_real import *
-else:
-    from trans_null import *
+__all__ = ['gettext', 'gettext_noop', 'gettext_lazy', 'ngettext',
+        'ngettext_lazy', 'string_concat', 'activate', 'deactivate',
+        'get_language', 'get_language_bidi', 'get_date_formats',
+        'get_partial_date_formats', 'check_for_language', 'to_locale',
+        'get_language_from_request', 'install']
+
+# Here be dragons, so a short explanation of the logic won't hurt:
+# We are trying to solve two problems: (1) access settings, in particular
+# settings.USE_I18N, as late as possible, so that modules can be imported
+# without having to first configure Django, and (2) if some other code creates
+# a reference to one of these functions, don't break that reference when we
+# replace the functions with their real counterparts (once we do access the
+# settings).
+
+def delayed_loader(*args, **kwargs):
+    """
+    Replace each real_* function with the corresponding function from either
+    trans_real or trans_null (e.g. real_gettext is replaced with
+    trans_real.gettext or trans_null.gettext). This function is run once, the
+    first time any i18n method is called. It replaces all the i18n methods at
+    once at that time.
+    """
+    import traceback
+    from django.conf import settings
+    if settings.USE_I18N:
+        import trans_real as trans
+    else:
+        import trans_null as trans
+    caller = traceback.extract_stack(limit=2)[0][2]
+    g = globals()
+    for name in __all__:
+        if hasattr(trans, name):
+            g['real_%s' % name] = getattr(trans, name)
+
+    # Make the originally requested function call on the way out the door.
+    return g[caller](*args, **kwargs)
+
+g = globals()
+for name in __all__:
+    g['real_%s' % name] = delayed_loader
+del g, delayed_loader
+
+def gettext_noop(message):
+    return real_gettext_noop(message)
+
+def gettext(message):
+    return real_gettext(message)
+
+
+def ngettext(singular, plural, number):
+    return real_ngettext(singular, plural, number)
+
+def string_concat(*strings):
+    return real_string_concat(*strings)
+
+ngettext_lazy = lazy(ngettext, str, unicode)
+gettext_lazy = lazy(gettext, str, unicode)
+string_concat = lazy(string_concat, str, unicode)
+
+def activate(language):
+    return real_activate(language)
+
+def deactivate():
+    return real_deactivate()
+
+def get_language():
+    return real_get_language()
+
+def get_language_bidi():
+    return real_get_language_bidi()
+
+def get_date_formats():
+    return real_get_date_formats()
+
+def get_partial_date_formats():
+    return real_get_partial_date_formats()
+
+def check_for_language(lang_code):
+    return real_check_for_language(lang_code)
+
+def to_locale(language):
+    return real_to_locale(language)
+
+def get_language_from_request(request):
+    return real_get_language_from_request(request)
+
+def install():
+    return real_install()
 
-del settings

django/utils/translation/trans_real.py

@@ -3,7 +3,6 @@
 import os, re, sys
 import gettext as gettext_module
 from cStringIO import StringIO
-from django.utils.functional import lazy
 
 try:
     import threading
@@ -277,9 +276,6 @@ def ngettext(singular, plural, number):
         _default = translation(settings.LANGUAGE_CODE)
     return _default.ngettext(singular, plural, number)
 
-gettext_lazy = lazy(gettext, str)
-ngettext_lazy = lazy(ngettext, str)
-
 def check_for_language(lang_code):
     """
     Checks whether there is a global language file for the given language code.
@@ -493,4 +489,3 @@ def string_concat(*strings):
     """
     return ''.join([str(el) for el in strings])
 
-string_concat = lazy(string_concat, str)