fix: Locale-aware currency formatting (#677)

* fix: Locale-aware currency formatting

Add locale-specific formatting for money display:
- French (fr): symbol after number with non-breaking space (1 000,12 €)
- German (de): symbol after number (1.000,12 €)
- Spanish (es): symbol after number (1.000,12 €)
- Italian (it): symbol after number (1.000,12 €)
- Portuguese-Brazil (pt-BR): symbol before with space (R$ 1.000,12)

This follows international conventions where most European languages
place the currency symbol after the number, unlike English.

* fix: Address CodeRabbit review comments

- Use non-breaking spaces (NBSP) for French locale formatting
- Add nil guard in locale_options to prevent NoMethodError
- Add test coverage for Portuguese (Brazil) locale

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

lib/money/formatting.rb

@@ -31,7 +31,35 @@ module Money::Formatting
     end
 
     def locale_options(locale)
-      case [ currency.iso_code, locale.to_sym ]
+      locale_sym = (locale || I18n.locale || :en).to_sym
+
+      # French locale: symbol after number with non-breaking space, comma as decimal separator
+      if locale_sym == :fr
+        return { delimiter: "\u00A0", separator: ",", format: "%n\u00A0%u" }
+      end
+
+      # German locale: symbol after number with space, comma as decimal separator
+      if locale_sym == :de
+        return { delimiter: ".", separator: ",", format: "%n %u" }
+      end
+
+      # Spanish locale: symbol after number with space, comma as decimal separator
+      if locale_sym == :es
+        return { delimiter: ".", separator: ",", format: "%n %u" }
+      end
+
+      # Italian locale: symbol after number with space, comma as decimal separator
+      if locale_sym == :it
+        return { delimiter: ".", separator: ",", format: "%n %u" }
+      end
+
+      # Portuguese (Brazil) locale: symbol before, comma as decimal separator
+      if locale_sym == :"pt-BR"
+        return { delimiter: ".", separator: ",", format: "%u %n" }
+      end
+
+      # Currency-specific overrides for remaining locales
+      case [ currency.iso_code, locale_sym ]
       when [ "EUR", :nl ], [ "EUR", :pt ]
         { delimiter: ".", separator: ",", format: "%u %n" }
       when [ "EUR", :en ], [ "EUR", :en_IE ]

test/lib/money_test.rb

@@ -90,6 +90,29 @@ class MoneyTest < ActiveSupport::TestCase
     assert_equal "€ 1.000,12", Money.new(1000.12, :eur).format(locale: :nl)
   end
 
+  test "formats correctly for French locale" do
+    # French uses non-breaking spaces (NBSP = \u00A0) between thousands and before currency symbol
+    assert_equal "1\u00A0000,12\u00A0€", Money.new(1000.12, :eur).format(locale: :fr)
+    assert_equal "1\u00A0000,12\u00A0$", Money.new(1000.12, :usd).format(locale: :fr)
+  end
+
+  test "formats correctly for German locale" do
+    assert_equal "1.000,12 €", Money.new(1000.12, :eur).format(locale: :de)
+    assert_equal "1.000,12 $", Money.new(1000.12, :usd).format(locale: :de)
+  end
+
+  test "formats correctly for Spanish locale" do
+    assert_equal "1.000,12 €", Money.new(1000.12, :eur).format(locale: :es)
+  end
+
+  test "formats correctly for Italian locale" do
+    assert_equal "1.000,12 €", Money.new(1000.12, :eur).format(locale: :it)
+  end
+
+  test "formats correctly for Portuguese (Brazil) locale" do
+    assert_equal "R$ 1.000,12", Money.new(1000.12, :brl).format(locale: :"pt-BR")
+  end
+
   test "converts currency when rate available" do
     ExchangeRate.expects(:find_or_fetch_rate).returns(OpenStruct.new(rate: 1.2))