Fixed #20477: Allowed list of modules for FORMAT_MODULE_PATH

Previously the FORMAT_MODULE_PATH setting only accepted one string (dotted
module path). A feature has been added to also allow a list of strings.

This is useful when using several reusable third party apps that define new
formats. We can now use them all and we can even override some of the formats
by providing a project-wide format module.

9 files changed, 74 insertions, 24 deletions

diff --git a/django/utils/formats.py b/django/utils/formats.py
index fc68179f3a..521ab5c763 100644
--- a/django/utils/formats.py
+++ b/django/utils/formats.py
@@ -46,21 +46,29 @@ def iter_format_modules(lang, format_module_path=None):
     """
     Does the heavy lifting of finding format modules.
     """
-    if check_for_language(lang):
-        format_locations = ['django.conf.locale.%s']
-        if format_module_path:
-            format_locations.append(format_module_path + '.%s')
-            format_locations.reverse()
-        locale = to_locale(lang)
-        locales = [locale]
-        if '_' in locale:
-            locales.append(locale.split('_')[0])
-        for location in format_locations:
-            for loc in locales:
-                try:
-                    yield import_module('%s.formats' % (location % loc))
-                except ImportError:
-                    pass
+    if not check_for_language(lang):
+        return
+
+    if format_module_path is None:
+        format_module_path = settings.FORMAT_MODULE_PATH
+
+    format_locations = []
+    if format_module_path:
+        if isinstance(format_module_path, six.string_types):
+            format_module_path = [format_module_path]
+        for path in format_module_path:
+            format_locations.append(path + '.%s')
+    format_locations.append('django.conf.locale.%s')
+    locale = to_locale(lang)
+    locales = [locale]
+    if '_' in locale:
+        locales.append(locale.split('_')[0])
+    for location in format_locations:
+        for loc in locales:
+            try:
+                yield import_module('%s.formats' % (location % loc))
+            except ImportError:
+                pass
 
 
 def get_format_modules(lang=None, reverse=False):
diff --git a/docs/ref/settings.txt b/docs/ref/settings.txt
index f82ced255b..acf42af7ad 100644
--- a/docs/ref/settings.txt
+++ b/docs/ref/settings.txt
@@ -1378,6 +1378,20 @@ like::
                 __init__.py
                 formats.py
 
+.. versionchanged:: 1.8
+
+    You can also set this setting to a list of Python paths, for example::
+
+        FORMAT_MODULE_PATH = [
+            'mysite.formats',
+            'some_app.formats',
+        ]
+
+    When Django searches for a certain format, it will go through all given
+    Python paths until it finds a module that actually defines the given
+    format. This means that formats defined in packages farther up in the list
+    will take precendence over the same formats in packages farther down.
+
 Available formats are :setting:`DATE_FORMAT`, :setting:`TIME_FORMAT`,
 :setting:`DATETIME_FORMAT`, :setting:`YEAR_MONTH_FORMAT`,
 :setting:`MONTH_DAY_FORMAT`, :setting:`SHORT_DATE_FORMAT`,
diff --git a/docs/releases/1.8.txt b/docs/releases/1.8.txt
index 21864aa3c2..b0e3b035c0 100644
--- a/docs/releases/1.8.txt
+++ b/docs/releases/1.8.txt
@@ -139,7 +139,10 @@ Forms
 Internationalization
 ^^^^^^^^^^^^^^^^^^^^
 
-* ...
+* :setting:`FORMAT_MODULE_PATH` can now be a list of strings representing
+  module paths. This allows importing several format modules from different
+  reusable apps. It also allows overriding those custom formats in your main
+  Django project.
 
 Management Commands
 ^^^^^^^^^^^^^^^^^^^
diff --git a/docs/topics/i18n/formatting.txt b/docs/topics/i18n/formatting.txt
index 04b36e2767..e726ddc808 100644
--- a/docs/topics/i18n/formatting.txt
+++ b/docs/topics/i18n/formatting.txt
@@ -154,11 +154,20 @@ Django provides format definitions for many locales, but sometimes you might
 want to create your own, because a format files doesn't exist for your locale,
 or because you want to overwrite some of the values.
 
-To use custom formats, specify the path where you'll place format files first.
-To do that, just set your :setting:`FORMAT_MODULE_PATH` setting to the package
-where format files will exist, for instance::
 
-    FORMAT_MODULE_PATH = 'mysite.formats'
+.. versionchanged:: 1.8
+
+    The ability to specify :setting:`FORMAT_MODULE_PATH` as a list was added.
+    Previously, only a single string value was supported.
+
+To use custom formats, specify the path where you'll place format files
+first. To do that, just set your :setting:`FORMAT_MODULE_PATH` setting to
+the package where format files will exist, for instance::
+
+    FORMAT_MODULE_PATH = [
+        'mysite.formats',
+        'some_app.formats',
+    ]
 
 Files are not placed directly in this directory, but in a directory named as
 the locale, and must be named ``formats.py``.
diff --git a/tests/i18n/other2/__init__.py b/tests/i18n/other2/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/other2/__init__.py
diff --git a/tests/i18n/other2/locale/__init__.py b/tests/i18n/other2/locale/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/other2/locale/__init__.py
diff --git a/tests/i18n/other2/locale/de/__init__.py b/tests/i18n/other2/locale/de/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/other2/locale/de/__init__.py
diff --git a/tests/i18n/other2/locale/de/formats.py b/tests/i18n/other2/locale/de/formats.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/other2/locale/de/formats.py
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index 8d0fc963af..d07c0d94a0 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -738,11 +738,27 @@ class FormattingTests(TestCase):
         """
         Tests the iter_format_modules function.
         """
+        # Importing some format modules so that we can compare the returned
+        # modules with these expected modules
+        default_mod = import_module('django.conf.locale.de.formats')
+        test_mod = import_module('i18n.other.locale.de.formats')
+        test_mod2 = import_module('i18n.other2.locale.de.formats')
+
         with translation.override('de-at', deactivate=True):
-            de_format_mod = import_module('django.conf.locale.de.formats')
-            self.assertEqual(list(iter_format_modules('de')), [de_format_mod])
-            test_de_format_mod = import_module('i18n.other.locale.de.formats')
-            self.assertEqual(list(iter_format_modules('de', 'i18n.other.locale')), [test_de_format_mod, de_format_mod])
+            # Should return the correct default module when no setting is set
+            self.assertEqual(list(iter_format_modules('de')), [default_mod])
+
+            # When the setting is a string, should return the given module and
+            # the default module
+            self.assertEqual(
+                list(iter_format_modules('de', 'i18n.other.locale')),
+                [test_mod, default_mod])
+
+            # When setting is a list of strings, should return the given
+            # modules and the default module
+            self.assertEqual(
+                list(iter_format_modules('de', ['i18n.other.locale', 'i18n.other2.locale'])),
+                [test_mod, test_mod2, default_mod])
 
     def test_iter_format_modules_stability(self):
         """