Fixed #27067 -- Deprecated string_concat() in favor of format_lazy().

AUTHORS

@@ -507,6 +507,7 @@ answer newbie questions, and generally made Django that much better:
     Matt Riggott
     Matt Robenolt <m@robenolt.com>
     Mattia Larentis <mattia@laretis.eu>
+    Mattias Loverot <mattias@stubin.se>
     mattycakes@gmail.com
     Max Burstein <http://maxburstein.com>
     Max Derkachev <mderk@yandex.ru>

django/contrib/admin/options.py

@@ -43,9 +43,9 @@ from django.utils.encoding import force_text, python_2_unicode_compatible
 from django.utils.html import escape, format_html
 from django.utils.http import urlencode, urlquote
 from django.utils.safestring import mark_safe
-from django.utils.text import capfirst, get_text_list
+from django.utils.text import capfirst, format_lazy, get_text_list
 from django.utils.translation import (
-    override as translation_override, string_concat, ugettext as _, ungettext,
+    override as translation_override, ugettext as _, ungettext,
 )
 from django.views.decorators.csrf import csrf_protect
 from django.views.generic import RedirectView
@@ -258,7 +258,7 @@ class BaseModelAdmin(six.with_metaclass(forms.MediaDefiningClass)):
         if isinstance(form_field.widget, SelectMultiple) and not isinstance(form_field.widget, CheckboxSelectMultiple):
             msg = _('Hold down "Control", or "Command" on a Mac, to select more than one.')
             help_text = form_field.help_text
-            form_field.help_text = string_concat(help_text, ' ', msg) if help_text else msg
+            form_field.help_text = format_lazy('{} {}', help_text, msg) if help_text else msg
         return form_field
 
     def get_view_on_site_url(self, obj=None):

django/contrib/postgres/utils.py

@@ -2,7 +2,7 @@ from __future__ import unicode_literals
 
 from django.core.exceptions import ValidationError
 from django.utils.functional import SimpleLazyObject
-from django.utils.translation import string_concat
+from django.utils.text import format_lazy
 
 
 def prefix_validation_error(error, prefix, code, params):
@@ -15,10 +15,11 @@ def prefix_validation_error(error, prefix, code, params):
         return ValidationError(
             # We can't simply concatenate messages since they might require
             # their associated parameters to be expressed correctly which
-            # is not something `string_concat` does. For example, proxied
+            # is not something `format_lazy` does. For example, proxied
             # ungettext calls require a count parameter and are converted
             # to an empty string if they are missing it.
-            message=string_concat(
+            message=format_lazy(
+                '{}{}',
                 SimpleLazyObject(lambda: prefix % params),
                 SimpleLazyObject(lambda: error.message % error_params),
             ),

django/db/models/options.py

@@ -22,8 +22,8 @@ from django.utils.encoding import (
     force_text, python_2_unicode_compatible, smart_text,
 )
 from django.utils.functional import cached_property
-from django.utils.text import camel_case_to_spaces
-from django.utils.translation import override, string_concat
+from django.utils.text import camel_case_to_spaces, format_lazy
+from django.utils.translation import override
 
 NOT_PROVIDED = object()
 
@@ -197,7 +197,7 @@ class Options(object):
             # verbose_name_plural is a special case because it uses a 's'
             # by default.
             if self.verbose_name_plural is None:
-                self.verbose_name_plural = string_concat(self.verbose_name, 's')
+                self.verbose_name_plural = format_lazy('{}s', self.verbose_name)
 
             # order_with_respect_and ordering are mutually exclusive.
             self._ordering_clash = bool(self.ordering and self.order_with_respect_to)
@@ -206,7 +206,7 @@ class Options(object):
             if meta_attrs != {}:
                 raise TypeError("'class Meta' got invalid attribute(s): %s" % ','.join(meta_attrs.keys()))
         else:
-            self.verbose_name_plural = string_concat(self.verbose_name, 's')
+            self.verbose_name_plural = format_lazy('{}s', self.verbose_name)
         del self.meta
 
         # If the db_table wasn't provided, use the app_label + model_name.

django/utils/translation/__init__.py

@@ -4,9 +4,11 @@ Internationalization support.
 from __future__ import unicode_literals
 
 import re
+import warnings
 
 from django.utils import six
 from django.utils.decorators import ContextDecorator
+from django.utils.deprecation import RemovedInDjango21Warning
 from django.utils.encoding import force_text
 from django.utils.functional import lazy
 
@@ -224,6 +226,10 @@ def _string_concat(*strings):
     Lazy variant of string concatenation, needed for translations that are
     constructed from multiple parts.
     """
+    warnings.warn(
+        'django.utils.translate.string_concat() is deprecated in '
+        'favor of django.utils.text.format_lazy().',
+        RemovedInDjango21Warning, stacklevel=2)
     return ''.join(force_text(s) for s in strings)
 string_concat = lazy(_string_concat, six.text_type)
 

docs/internals/deprecation.txt

@@ -25,6 +25,8 @@ details on these changes.
 
 * ``django.test.runner.setup_databases()`` will be removed.
 
+* ``django.utils.translation.string_concat()`` will be removed.
+
 .. _deprecation-removed-in-2.0:
 
 2.0

docs/ref/utils.txt

@@ -1107,6 +1107,12 @@ For a complete discussion on the usage of the following see the
 
 .. function:: string_concat(*strings)
 
+    .. deprecated:: 1.11
+
+        Use :meth:`django.utils.text.format_lazy` instead.
+        ``string_concat(*strings)`` can be replaced by
+        ``format_lazy('{}' * len(strings), *strings)``.
+
     Lazy variant of string concatenation, needed for translations that are
     constructed from multiple parts.
 

docs/releases/1.11.txt

@@ -477,3 +477,7 @@ Miscellaneous
 
 * ``django.test.runner.setup_databases()`` is moved to
   :func:`django.test.utils.setup_databases`. The old location is deprecated.
+
+* ``django.utils.translation.string_concat()`` is deprecated in
+  favor of :func:`django.utils.text.format_lazy`. ``string_concat(*strings)``
+  can be replaced by ``format_lazy('{}' * len(strings), *strings)``.

docs/topics/i18n/translation.txt

@@ -489,21 +489,22 @@ directly with the ``number`` argument::
                 raise forms.ValidationError(self.error_message % number)
 
 
-Joining strings: ``string_concat()``
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Formatting strings: ``format_lazy()``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Standard Python string joins (``''.join([...])``) will not work on lists
-containing lazy translation objects. Instead, you can use
-:func:`django.utils.translation.string_concat()`, which creates a lazy object
-that concatenates its contents *and* converts them to strings only when the
-result is included in a string. For example::
+Python's :meth:`str.format()` method will not work when either the
+``format_string`` or any of the arguments to :meth:`str.format()`
+contains lazy translation objects. Instead, you can use
+:func:`django.utils.text.format_lazy()`, which creates a lazy object
+that runs the ``str.format()`` method only when the result is included
+in a string. For example::
 
-    from django.utils.translation import string_concat
+    from django.utils.text import format_lazy
     from django.utils.translation import ugettext_lazy
     ...
     name = ugettext_lazy('John Lennon')
     instrument = ugettext_lazy('guitar')
-    result = string_concat(name, ': ', instrument)
+    result = format_lazy('{name}: {instrument}', name=name, instrument=instrument)
 
 In this case, the lazy translations in ``result`` will only be converted to
 strings when ``result`` itself is used in a string (usually at template

tests/i18n/tests.py

@@ -16,10 +16,12 @@ from django.conf import settings
 from django.conf.urls.i18n import i18n_patterns
 from django.template import Context, Template, TemplateSyntaxError
 from django.test import (
-    RequestFactory, SimpleTestCase, TestCase, override_settings,
+    RequestFactory, SimpleTestCase, TestCase, ignore_warnings,
+    override_settings,
 )
 from django.utils import six, translation
 from django.utils._os import upath
+from django.utils.deprecation import RemovedInDjango21Warning
 from django.utils.formats import (
     date_format, get_format, get_format_modules, iter_format_modules, localize,
     localize_input, reset_format_cache, sanitize_separators, time_format,
@@ -417,6 +419,7 @@ class TranslationTests(SimpleTestCase):
                     ' super results{% endblocktrans %}'
                 )
 
+    @ignore_warnings(category=RemovedInDjango21Warning)
     def test_string_concat(self):
         """
         six.text_type(string_concat(...)) should not raise a TypeError - #4796