MONGOID-5910 Implement enumerable methods on top level models (any?, many?, and one?)

lib/mongoid/criteria/findable.rb

@@ -81,6 +81,36 @@ def multiple_from_db(ids)
         ids.empty? ? [] : from_database(ids)
       end
 
+      # Return true if any documents exist in the criteria.
+      #
+      # @example Determine if any documents exist
+      #   criteria.any?
+      #
+      # @return [ true | false ] If any documents exist.
+      def any?
+        limit(1).count > 0
+      end
+
+      # Return true if only one document exists in the criteria.
+      #
+      # @example Determine if only one document exists
+      #   criteria.one?
+      #
+      # @return [ true | false ] If only one document exists.
+      def one?
+        limit(2).count == 1
+      end
+
+      # Return true if more than one document exists in the criteria.
+      #
+      # @example Determine if many documents exist
+      #   criteria.many?
+      #
+      # @return [ true | false ] If many documents exist.
+      def many?
+        limit(2).count > 1
+      end
+
       private
 
       # Get the finder used to generate the id query.

lib/mongoid/findable.rb

@@ -17,6 +17,7 @@ module Findable
     # directly from the class level.
     def_delegators :with_default_scope,
       :aggregates,
+      :any?,
       :avg,
       :create_with,
       :distinct,
@@ -40,10 +41,12 @@ module Findable
       :fourth!,
       :includes,
       :last!,
+      :many?,
       :map_reduce,
       :max,
       :min,
       :none,
+      :one?,
       :pick,
       :pluck,
       :raw,

spec/mongoid/criteria/findable_spec.rb

@@ -1302,6 +1302,212 @@
     end
   end
 
+  describe "#any?" do
+    context "when called on criteria" do
+      let!(:band) do
+        Band.create!(name: "Depeche Mode")
+      end
+
+      let!(:band_two) do
+        Band.create!(name: "Radiohead")
+      end
+
+      context "when documents exist" do
+
+        let(:criteria) do
+          Band.all
+        end
+
+        it "returns true" do
+          expect(criteria.any?).to be true
+        end
+      end
+
+      context "when no documents exist" do
+
+        let(:criteria) do
+          Band.where(name: "Nonexistent Band")
+        end
+
+        it "returns false" do
+          expect(criteria.any?).to be false
+        end
+      end
+    end
+
+    context "when called on class" do
+      context "with documents" do
+        before do
+          Band.create!(name: "New Band")
+        end
+
+        it "returns true" do
+          expect(Band.any?).to be true
+        end
+      end
+
+      context "with no documents" do
+        before do
+          Band.delete_all
+        end
+        it "returns false" do
+          expect(Band.any?).to be false
+        end
+      end
+    end
+  end
+
+  describe "#one?" do
+    context "when called on criteria" do
+      let!(:band) do
+        Band.create!(name: "Depeche Mode")
+      end
+
+      let!(:band_two) do
+        Band.create!(name: "Radiohead")
+      end
+
+      context "when one document exists in criteria" do
+        let(:criteria) do
+          Band.where(name: "Depeche Mode")
+        end
+
+        it "returns true" do
+          expect(criteria.one?).to be true
+        end
+      end
+
+      context "when multiple documents exist in criteria" do
+        let(:criteria) do
+          Band.all
+        end
+
+        it "returns false" do
+          expect(criteria.one?).to be false
+        end
+      end
+
+      context "when no documents exist in criteria" do
+        let(:criteria) do
+          Band.where(name: "Nonexistent Band")
+        end
+
+        it "returns false" do
+          expect(criteria.one?).to be false
+        end
+      end
+    end
+
+    context "when called on class" do
+      context "with no documents" do
+        before do # can maybe delete this - not sure how cleanup works here
+          Band.delete_all
+        end
+
+        it "returns false" do
+          expect(Band.one?).to be false
+        end
+      end
+
+      context "with one document" do
+        before do
+          Band.create!(name: "Another Band")
+        end
+
+        it "returns true" do
+          expect(Band.one?).to be true
+        end
+      end
+
+      context "with multiple documents" do
+        before do
+          Band.create!(name: "New Band")
+          Band.create!(name: "Yet Another Band")
+        end
+
+        it "returns false" do
+          expect(Band.one?).to be false
+        end
+      end
+    end
+  end
+
+  describe "#many?" do
+    context "when called on criteria" do
+      let!(:band) do
+        Band.create!(name: "Depeche Mode")
+      end
+
+      let!(:band_two) do
+        Band.create!(name: "Radiohead")
+      end
+
+      context "when multiple documents exist in criteria" do
+        let(:criteria) do
+          Band.all
+        end
+
+        it "returns true" do
+          expect(criteria.many?).to be true
+        end
+      end
+
+      context "when one document exists in criteria" do
+        let(:criteria) do
+          Band.where(name: "Depeche Mode")
+        end
+
+        it "returns false" do
+          expect(criteria.many?).to be false
+        end
+      end
+
+      context "when no documents exist in criteria" do
+        let(:criteria) do
+          Band.where(name: "Nonexistent Band")
+        end
+
+        it "returns false" do
+          expect(criteria.many?).to be false
+        end
+      end
+
+    end
+
+    context "when called on class" do
+      context "with no documents" do
+        before do
+          Band.delete_all
+        end
+
+        it "returns false" do
+          expect(Band.many?).to be false
+        end
+      end
+
+      context "with one document" do
+        before do
+          Band.create!(name: "Another Band")
+        end
+
+        it "returns false" do
+          expect(Band.many?).to be false
+        end
+      end
+
+      context "with multiple documents" do
+        before do
+          Band.create!(name: "New Band")
+          Band.create!(name: "Yet Another Band")
+        end
+
+        it "returns true" do
+          expect(Band.many?).to be true
+        end
+      end
+    end
+  end
+
   describe '#from_database_selector' do
     let(:criteria) { Mongoid::Criteria.new(Band) }
     let(:result) { criteria.send(:from_database_selector, [1]) }