From 741845cfec0701a0240ed320b0e29a915a7f2dc1 Mon Sep 17 00:00:00 2001
From: Ryan Bigg <me@ryanbigg.com>
Date: Wed, 15 Jul 2020 10:05:16 +1000
Subject: [PATCH] Always instantiate I18n::Locale::Fallbacks objects when using
 I18n.fallbacks=

---
 lib/i18n/backend/fallbacks.rb  |  2 +-
 test/backend/fallbacks_test.rb | 19 +++++++++++++++++++
 test/locale/fallbacks_test.rb  |  7 +++++++
 test/test_helper.rb            |  1 +
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/lib/i18n/backend/fallbacks.rb b/lib/i18n/backend/fallbacks.rb
index 7188a82c..40ff1220 100644
--- a/lib/i18n/backend/fallbacks.rb
+++ b/lib/i18n/backend/fallbacks.rb
@@ -20,7 +20,7 @@ def fallbacks
 
     # Sets the current fallbacks implementation. Use this to set a different fallbacks implementation.
     def fallbacks=(fallbacks)
-      @@fallbacks = fallbacks
+      @@fallbacks = fallbacks.is_a?(I18n::Locale::Fallbacks) ? fallbacks : I18n::Locale::Fallbacks.new(fallbacks)
     end
   end
 
diff --git a/test/backend/fallbacks_test.rb b/test/backend/fallbacks_test.rb
index b7246877..688efd4a 100644
--- a/test/backend/fallbacks_test.rb
+++ b/test/backend/fallbacks_test.rb
@@ -109,6 +109,25 @@ def setup
   end
 end
 
+# See Issue #534
+class I18nBackendFallbacksLocalizeTestWithDefaultLocale < I18n::TestCase
+  class Backend < I18n::Backend::Simple
+    include I18n::Backend::Fallbacks
+  end
+
+  def setup
+    super
+    I18n.backend = Backend.new
+    I18n.enforce_available_locales = false
+    I18n.fallbacks = [I18n.default_locale]
+    store_translations(:en, time: { formats: { long: 'en fallback' } })
+  end
+
+  test "falls back to default locale - Issue #534" do
+    assert_equal 'en fallback', I18n.l(Time.now, format: :long, locale: "un-supported")
+  end
+end
+
 class I18nBackendFallbacksLocalizeTest < I18n::TestCase
   class Backend < I18n::Backend::Simple
     include I18n::Backend::Fallbacks
diff --git a/test/locale/fallbacks_test.rb b/test/locale/fallbacks_test.rb
index 8e2a2b47..dbfca921 100644
--- a/test/locale/fallbacks_test.rb
+++ b/test/locale/fallbacks_test.rb
@@ -22,6 +22,13 @@ class I18nFallbacksDefaultsTest < I18n::TestCase
     assert_equal [:"de-CH", :de, :"en-GB", :en], fallbacks[:"de-CH"]
   end
 
+  test "explicit fallback to default locale" do
+    I18n.default_locale = :"en-US"
+    fallbacks = Fallbacks.new([:"en-US"])
+    assert_equal [:"de-AT", :de, :"en-US", :en], fallbacks[:"de-AT"]
+    assert_equal [:"de-CH", :de, :"en-US", :en], fallbacks[:"de-CH"]
+  end
+
   test "defaults reflect a manually passed default locale if any" do
     fallbacks = Fallbacks.new(:'fi-FI')
     assert_equal [:'fi-FI', :fi], fallbacks.defaults
diff --git a/test/test_helper.rb b/test/test_helper.rb
index d4a8488f..8477fef5 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -34,6 +34,7 @@ def teardown
     I18n.backend = nil
     I18n.default_separator = nil
     I18n.enforce_available_locales = true
+    I18n.fallbacks = nil
     super
   end