Allow time dimensions for date columns

lib/active_reporting/dimension.rb

@@ -3,6 +3,7 @@
 module ActiveReporting
   class Dimension
     TYPES = { degenerate: :degenerate, standard: :standard }.freeze
+    TIME_COLUMN_TYPES = %i[datetime date].freeze
     attr_reader :name
 
     # @param model [ActiveRecord::Base]
@@ -30,11 +31,13 @@ def type
                 end
     end
 
-    # Whether the dimension is a datetime column
+    # Whether the dimension is a datetime or date column
     #
     # @return [Boolean]
     def datetime?
-      @datetime ||= type == TYPES[:degenerate] && model.column_for_attribute(@name).type == :datetime
+      @datetime ||= type == TYPES[:degenerate] && TIME_COLUMN_TYPES.include?(
+        model.column_for_attribute(@name).type
+      )
     end
 
     # Tells if the dimension is hierarchical

test/active_reporting/report_test.rb

@@ -32,6 +32,29 @@ def test_report_runs_with_an_aggregate_other_than_count
     assert data.all? { |r| r.key?('a_metric') }
   end
 
+  def test_report_runs_with_a_year_grouping
+    if ENV['DB'] == 'pg'
+      metric = ActiveReporting::Metric.new(
+        :a_metric,
+        fact_model: UserFactModel,
+        dimensions: [{birthday_on: :year}]
+      )
+      report = ActiveReporting::Report.new(metric)
+      data = report.run
+      assert data.all? { |r| r.key?('birthday_on_year') }
+      assert data.size == 5
+    else
+      assert_raises ActiveReporting::InvalidDimensionLabel do
+        metric = ActiveReporting::Metric.new(
+          :a_metric,
+          fact_model: UserFactModel,
+          dimensions: [{birthday_on: :year}]
+        )
+        report = ActiveReporting::Report.new(metric)
+      end
+    end
+  end
+
   def test_report_runs_with_a_date_grouping
     if ENV['DB'] == 'pg'
       metric = ActiveReporting::Metric.new(:a_metric, fact_model: UserFactModel, dimensions: [{created_at: :month}])

test/fact_models.rb

@@ -39,6 +39,7 @@ class DateDimensionFactModel < ActiveReporting::FactModel
 
 class UserFactModel < ActiveReporting::FactModel
   default_dimension_label :username
+  dimension :birthday_on
   dimension :created_at
 end
 

test/schema.rb

@@ -57,6 +57,7 @@
 
   create_table :users, force: true do |t|
     t.string :username
+    t.date :birthday_on
     t.timestamps null: false
   end
 

test/seed.rb

@@ -5,6 +5,7 @@
 (1..5).each do |i|
   user = User.create!(
     created_at: Time.now - i.months,
+    birthday_on: (10 + i).years.ago ,
     username: "user_#{i}"
   )