MONGOID-5125 find: does not return the correct results for has_many relations (#5012)

Co-authored-by: Dmitry Rybakov <dmitry.rybakov@mongodb.com>

Author: bradrees

lib/mongoid/association/embedded/embeds_many/proxy.rb

@@ -210,17 +210,29 @@ def exists?
           # Finds a document in this association through several different
           # methods.
           #
+          # This method delegates to +Mongoid::Criteria#find+. If this method is
+          # not given a block, it returns one or many documents for the provided
+          # _id values.
+          #
+          # If this method is given a block, it returns the first document
+          # of those found by the current Criteria object for which the block
+          # returns a truthy value.
+          #
           # @example Find a document by its id.
           #   person.addresses.find(BSON::ObjectId.new)
           #
           # @example Find documents for multiple ids.
           #   person.addresses.find([ BSON::ObjectId.new, BSON::ObjectId.new ])
           #
+          # @example Finds the first matching document using a block.
+          #   person.addresses.find { |addr| addr.state == 'CA' }
+          #
           # @param [ Array<Object> ] args Various arguments.
+          # @param [ Proc ] block Optional block to pass.
           #
-          # @return [ Array<Document>, Document ] A single or multiple documents.
-          def find(*args)
-            criteria.find(*args)
+          # @return [ Document | Array<Document> | nil ] A document or matching documents.
+          def find(*args, &block)
+            criteria.find(*args, &block)
           end
 
           # Instantiate a new embeds_many association.

lib/mongoid/association/referenced/has_many/proxy.rb

@@ -185,25 +185,37 @@ def exists?
             criteria.exists?
           end
 
-          # Find the matchind document on the association, either based on id or
+          # Find the matching document on the association, either based on id or
           # conditions.
           #
+          # This method delegates to +Mongoid::Criteria#find+. If this method is
+          # not given a block, it returns one or many documents for the provided
+          # _id values.
+          #
+          # If this method is given a block, it returns the first document
+          # of those found by the current Criteria object for which the block
+          # returns a truthy value.
+          #
           # @example Find by an id.
           #   person.posts.find(BSON::ObjectId.new)
           #
           # @example Find by multiple ids.
           #   person.posts.find([ BSON::ObjectId.new, BSON::ObjectId.new ])
           #
+          # @example Finds the first matching document using a block.
+          #   person.addresses.find { |addr| addr.state == 'CA' }
+          #
           # @note This will keep matching documents in memory for iteration
           #   later.
           #
           # @param [ BSON::ObjectId, Array<BSON::ObjectId> ] args The ids.
+          # @param [ Proc ] block Optional block to pass.
           #
-          # @return [ Document, Criteria ] The matching document(s).
+          # @return [ Document | Array<Document> | nil ] A document or matching documents.
           #
           # @since 2.0.0.beta.1
-          def find(*args)
-            matching = criteria.find(*args)
+          def find(*args, &block)
+            matching = criteria.find(*args, &block)
             Array(matching).each { |doc| _target.push(doc) }
             matching
           end

spec/mongoid/association/embedded/embeds_many/proxy_spec.rb

@@ -1417,12 +1417,12 @@ class TrackingIdValidationHistory
         expect(person.addresses.any?).to be true
       end
     end
-    
+
     context "when documents are not persisted" do
       before do
         person.addresses.build(street: "Bond")
       end
-      
+
       it "returns true" do
         expect(person.addresses.any?).to be true
       end
@@ -2148,6 +2148,44 @@ class TrackingIdValidationHistory
         end
       end
     end
+
+    context "with block" do
+      let!(:author) do
+        Person.create!(title: 'Person')
+      end
+
+      let!(:video_one) do
+        author.videos.create!(title: 'video one')
+      end
+
+      let!(:video_two) do
+        author.videos.create!(title: 'video two')
+      end
+
+      it "finds one" do
+        expect(
+          author.videos.find do |video|
+            video.title == 'video one'
+          end
+        ).to eq(video_one)
+      end
+
+      it "returns first match of multiple" do
+        expect(
+          author.videos.find do |video|
+            ['video one', 'video two'].include?(video.title)
+          end
+        ).to be_a(Video)
+      end
+
+      it "returns nil when not found" do
+        expect(
+          author.videos.find do |video|
+            video.title == 'non exiting one'
+          end
+        ).to be_nil
+      end
+    end
   end
 
   describe "#find_or_create_by" do

spec/mongoid/association/referenced/has_many/proxy_spec.rb

@@ -2709,6 +2709,44 @@
         end
       end
     end
+
+    context "with block" do
+      let!(:author) do
+        Person.create!(title: 'Person')
+      end
+
+      let!(:post_one) do
+        author.posts.create!(title: 'post one')
+      end
+
+      let!(:post_two) do
+        author.posts.create!(title: 'post two')
+      end
+
+      it "finds one" do
+        expect(
+          author.posts.find do |post|
+            post.title == 'post one'
+          end
+        ).to be_a(Post)
+      end
+
+      it "returns first match of multiple" do
+        expect(
+          author.posts.find do |post|
+            ['post one', 'post two'].include?(post.title)
+          end
+        ).to eq(post_one)
+      end
+
+      it "returns nil when not found" do
+        expect(
+          author.posts.find do |post|
+            post.title == 'non exiting one'
+          end
+        ).to be_nil
+      end
+    end
   end
 
   describe "#find_or_create_by" do