Localise Dates (thoughtbot#570)

* Reorder I18n backends in `with_translations` helper

The `with_translations` helper allows translations to be setup for a
method under test. A recent change (thoughtbot#772) added a backend chain to
ensure this helper won't break other spec by replacing all translations
and causing "missing_translations" failures.

This changes the order of the I18n backends so that specs will first use
the translations provided to the `with_translations` block and then
fallback to the default translations. Otherwise, there would be no way
to override the default translations in test cases.

* Adds format option to DateTime field

Updates DateTime field to accept 'format' option which determines
the display format of the field. The option can be
* A key for the localized date format in the corresponding yaml config
file
* A strftime format string

app/views/fields/date_time/_index.html.erb

@@ -17,5 +17,5 @@ as a localized date & time string.
 %>
 
 <% if field.data %>
-  <%= l field.data.to_date %>
+  <%= field.date %>
 <% end %>

app/views/fields/date_time/_show.html.erb

@@ -17,5 +17,5 @@ as a localized date & time string.
 %>
 
 <% if field.data %>
-  <%= l(field.data, default: field.data) %>
+  <%= field.datetime %>
 <% end %>

lib/administrate/field/date_time.rb

@@ -3,6 +3,19 @@
 module Administrate
   module Field
     class DateTime < Base
+      def date
+        I18n.localize(data.to_date, format: format)
+      end
+
+      def datetime
+        I18n.localize(data, format: format, default: data)
+      end
+
+      private
+
+      def format
+        options.fetch(:format, :default)
+      end
     end
   end
 end

spec/lib/fields/date_time_spec.rb

@@ -1,6 +1,82 @@
-require "spec_helper"
+require "rails_helper"
 require "administrate/field/date_time"
-require "support/field_matchers"
 
 describe Administrate::Field::DateTime do
+  let(:start_date) { DateTime.parse("2015-12-25 10:15:45") }
+  let(:formats) do
+    {
+      date: {
+        formats: { default: "%m/%d/%Y", short: "%b %d" },
+        abbr_month_names: Array.new(13) { |i| "Dec" if i == 12 },
+        abbr_day_names: Array.new(7) { |i| "Fri" if i == 5 },
+      },
+      time: {
+        formats: { default: "%a, %b %-d, %Y at %r", short: "%d %b %H:%M" },
+      },
+    }
+  end
+
+  describe "#date" do
+    it "displays the date" do
+      with_translations(:en, formats) do
+        field = Administrate::Field::DateTime.
+          new(:start_date, start_date, :show)
+        expect(field.date).to eq("12/25/2015")
+      end
+    end
+
+    context "with `prefix` option" do
+      it "displays the date in the requested format" do
+        options_field = Administrate::Field::DateTime.
+          with_options(format: :short)
+        field = options_field.new(:start_date, start_date, :show)
+
+        with_translations(:en, formats) do
+          expect(field.date).to eq("Dec 25")
+        end
+      end
+
+      it "displays the date using a format string" do
+        options_field = Administrate::Field::DateTime.
+          with_options(format: "%Y")
+        field = options_field.new(:start_date, start_date, :show)
+
+        with_translations(:en, formats) do
+          expect(field.date).to eq("2015")
+        end
+      end
+    end
+  end
+
+  describe "#datetime" do
+    it "displays the datetime" do
+      field = Administrate::Field::DateTime.new(:start_date, start_date, :show)
+
+      with_translations(:en, formats) do
+        expect(field.datetime).to eq("Fri, Dec 25, 2015 at 10:15:45 AM")
+      end
+    end
+
+    context "with `prefix` option" do
+      it "displays the datetime in the requested format" do
+        options_field = Administrate::Field::DateTime.
+          with_options(format: :short)
+        field = options_field.new(:start_date, start_date, :show)
+
+        with_translations(:en, formats) do
+          expect(field.datetime).to eq("25 Dec 10:15")
+        end
+      end
+
+      it "displays the datetime format string" do
+        options_field = Administrate::Field::DateTime.
+          with_options(format: "%H:%M")
+        field = options_field.new(:start_date, start_date, :show)
+
+        with_translations(:en, formats) do
+          expect(field.datetime).to eq("10:15")
+        end
+      end
+    end
+  end
 end

spec/support/i18n.rb

@@ -7,7 +7,7 @@ def with_translations(locale, translations)
     new_backend = I18n::Backend::KeyValue.new({}, true)
     new_backend.store_translations(locale, translations)
 
-    I18n.backend = I18n::Backend::Chain.new(original_backend, new_backend)
+    I18n.backend = I18n::Backend::Chain.new(new_backend, original_backend)
 
     yield
   ensure