MONGOID-5147 Add missing find_first & one methods to Mongoid::Contextual::None (#5044)

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: p-mongo

lib/mongoid/contextual/none.rb

@@ -112,6 +112,9 @@ def length
         entries.length
       end
       alias :size :length
+
+      alias :find_first :first
+      alias :one :first
     end
   end
 end

spec/integration/contextual/empty_spec.rb

@@ -0,0 +1,142 @@
+# frozen_string_literal: true
+# encoding: utf-8
+
+require 'spec_helper'
+
+describe 'Contextual classes when dealing with empty result set' do
+  shared_examples 'behave as expected' do
+    context '#exists?' do
+      it 'is false' do
+        context.exists?.should be false
+      end
+    end
+
+    context '#count' do
+      it 'is 0' do
+        context.count.should == 0
+      end
+    end
+
+    context '#length' do
+      it 'is 0' do
+        context.length.should == 0
+      end
+    end
+
+    # #estimated_count only exists for Mongo
+
+    context '#distinct' do
+      it 'is empty array' do
+        context.distinct(:foo).should == []
+      end
+    end
+
+    context '#each' do
+      context 'with block' do
+        it 'does not invoke the block' do
+          called = false
+          context.each do
+            called = true
+          end
+          called.should be false
+        end
+      end
+
+      context 'without block' do
+        it 'returns Enumerable' do
+          context.each.should be_a(Enumerable)
+        end
+
+        it 'returns empty Enumerable' do
+          context.each.to_a.should == []
+        end
+      end
+    end
+
+    context '#map' do
+      context 'with block' do
+        it 'does not invoke the block' do
+          called = false
+          context.map do
+            called = true
+          end
+          called.should be false
+        end
+      end
+
+      context 'without block' do
+        it 'returns empty array' do
+          skip 'MONGOID-5148'
+
+          context.map(:field).should == []
+        end
+      end
+    end
+
+    context '#first' do
+      it 'is nil' do
+        context.first.should be nil
+      end
+    end
+
+    context '#find_first' do
+      it 'is nil' do
+        context.find_first.should be nil
+      end
+    end
+
+    context '#one' do
+      it 'is nil' do
+        context.one.should be nil
+      end
+    end
+
+    context '#last' do
+      it 'is nil' do
+        context.last.should be nil
+      end
+    end
+  end
+
+  let(:context) do
+    context_cls.new(criteria)
+  end
+
+  before do
+    # Create an object of the same class used in the Criteria instance
+    # to verify we are using the Contextual classes.
+    Mop.create!
+  end
+
+  context 'Mongo' do
+    let(:context_cls) { Mongoid::Contextual::Mongo }
+
+    let(:criteria) do
+      Mop.and(Mop.where(a: 1), Mop.where(a: 2))
+    end
+
+    include_examples 'behave as expected'
+  end
+
+  context 'Memory' do
+    let(:context_cls) { Mongoid::Contextual::Memory }
+
+    let(:criteria) do
+      Mop.all.tap do |criteria|
+        criteria.documents = []
+      end
+    end
+
+    include_examples 'behave as expected'
+  end
+
+  context 'None' do
+    let(:context_cls) { Mongoid::Contextual::None }
+
+    let(:criteria) do
+      Mop.none
+    end
+
+    include_examples 'behave as expected'
+  end
+end