Document translation fallback behavior change in 1.8

[Nicola]

I updated from 1.7 to 1.8

in my templates and python code I have string in my native language (italian),

so my po files look likes this:

1) locale en

msgid "original string in italian"
msgstr "english translated string"

2) locale it

msgid "original string in italian"
msgstr ""

now in settings I have:

LANGUAGE_CODE = 'en'

my browser is in italian so request.LANGUAGE_CODE is "it"

in django <1.8 the fallback translation is taken from the it po file, in django 1.8+ en translation is used since my default LANGUAGE_CODE is "en", if I set LANGUAGE_CODE to "it" the fallback string from it po file is used

[Tim Graham]

Reproduced and bisected to a5f6cbce07b5f3ab48d931e3fd1883c757fb9b45.

[Claude Paroz]

Apart from the unexpected change, isn't the new behavior the most correct?

Maybe you might check that master keeps this behavior, as [3cf1c02695481900] touched this part of the code. But at first sight, it shouldn't affect the use case you described.

[Nicola]

New behaviour:

• if a string is not translated for a locale django use the translated string (if any) from the default locale

Old behaviour:

• if a string is not translated for a locale django use the untranslated string for the same locale

what is most correct is an opinion, I like the old behaviour since all untranslated strings should be equals,

your opinion could be that an untranslated string should show the value for the default locale and not the untranslated one

however is easy enouth to use a tool like poedit to copy all the translations from the original string, so if you like more the new behaviour is just a matter to document it

[Tim Graham]

Claude, could you propose a patch (docs or otherwise) at your convenience?

[Claude Paroz]

#24503 was partially related.

What about:

docs/releases/1.8.txt

@@ -1159 +1159 @@
 * :func:`django.utils.translation.get_language()` now returns ``None`` instead
   of :setting:`LANGUAGE_CODE` when translations are temporarily deactivated.
 
+* When a translation doesn't exist for a specific literal, the fallback is now
+  taken from the :setting:`LANGUAGE_CODE` language (instead of the untranslated
+  ``msgid`` message).
+
 * The ``name`` field of :class:`django.contrib.contenttypes.models.ContentType`
   has been removed by a migration and replaced by a property. That means it's
   not possible to query or filter a ``ContentType`` by this field any longer.

[Tim Graham]

I'd suggest "instead of from the" -- otherwise, good!

[Claude Paroz <claude@…>]

In 1046c8af:

Fixed #24739 -- Documented translation fallback change

Refs #24503.

[Claude Paroz <claude@…>]

In 7915cbb:

[1.8.x] Fixed #24739 -- Documented translation fallback change

Refs #24503.
Backport of 1046c8afec from master.