FIND-13339: Cyclic queries

- Update BaseTypeQueryBuilder & FragmentBuilder to allow cyclic fragment

Author: ManhOptimizely

APIs/src/EpiServer.ContentGraph/Api/Querying/BaseTypeQueryBuilder.cs

@@ -206,7 +206,15 @@ private IEnumerable<FragmentBuilder> GetAllChildren(FragmentBuilder fragment)
             {
                 foreach (var child in fragment.ChildrenFragments)
                 {
-                    yield return child;
+                    if (Parent.HasFragment(child.GetName()))
+                    {
+                        continue;
+                    }
+                    else
+                    {
+                        yield return child;
+                    }
+                    
                     if (child.HasChildren)
                     {
                         foreach (var item in GetAllChildren(child))

APIs/src/EpiServer.ContentGraph/Api/Querying/FragmentBuilder.cs

@@ -60,12 +60,9 @@ public override FragmentBuilder AddFragments(params FragmentBuilder[] fragments)
             }
             return this;
         }
-        public FragmentBuilder AddFragment(string path, FragmentBuilder fragment)
+        public override FragmentBuilder AddFragment(string path, FragmentBuilder fragment)
         {
-            if (_childrenFragments.IsNull())
-            {
-                _childrenFragments = new List<FragmentBuilder>();
-            }
+            _childrenFragments ??= new List<FragmentBuilder>();
             base.AddFragment(path, fragment);
             _childrenFragments.Add(fragment);
 

APIs/src/EpiServer.ContentGraph/Api/Querying/GraphQueryBuilder.cs

@@ -98,10 +98,7 @@ public void AddFragment(FragmentBuilder fragmentBuilder)
             {
                 _fragmentBuilders = new Dictionary<string, FragmentBuilder>();
             }
-            if (!_fragmentBuilders.TryAdd(fragmentBuilder.GetName(), fragmentBuilder))
-            {
-                throw new ArgumentException($"Fragment [{fragmentBuilder.GetName()}] had added already.");
-            }
+            _fragmentBuilders.TryAdd(fragmentBuilder.GetName(), fragmentBuilder);
         }
         public IEnumerable<FragmentBuilder> GetFragments()
         {
@@ -328,5 +325,10 @@ public void AddQuery(string typeQuery)
         {
             typeQueries.Add(typeQuery);
         }
+
+        public bool HasFragment(string fragmentName)
+        {
+            return _fragmentBuilders.ContainsKey(fragmentName);
+        }
     }
 }

APIs/src/EpiServer.ContentGraph/Api/Querying/IQuery.cs

@@ -8,6 +8,7 @@ public interface IQuery
         public Task<ContentGraphResult<TResult>> GetResultAsync<TResult>();
         public Task<ContentGraphResult> GetResultAsync();
         internal void AddFragment(FragmentBuilder fragmentBuilder);
+        internal bool HasFragment(string fragmentName);
         internal void AddQuery(string typeQuery);
     }
 }

APIs/src/Testing/EpiServer.ContentGraph.UnitTests/GenerateFragmentTests.cs

@@ -225,5 +225,49 @@ public void fragment_on_field_should_generate_correct_query()
             //expect full query
             Assert.Equal(expectedFullQuery, graphQueryBuilder.GetQuery().Query);
         }
+        [Fact]
+        public void cyclic_fragments_should_generate_correct_query()
+        {
+            const string expectedMainQuery = "query FragmentTest {FragmentObject{items{Name ...FirstFragment ...SecondFragment}}}";
+            const string expectedFistFragment = "fragment FirstFragment on PromoExtend {ProviderName Details{PromoImage{PromoExtend{...FirstFragment}}}}";
+            const string expectedSecondFragmment = "fragment SecondFragment on PromoObject {Url PromoExtend{...ThirdFragment}}";
+            const string expectedThirdFragmment = "fragment ThirdFragment on PromoExtend {ProviderName PromoExtend{...SecondFragment}}";
+            const string expectedFullQuery = $"{expectedMainQuery}\n{expectedFistFragment}\n{expectedSecondFragmment}\n{expectedThirdFragmment}";
+            //Self-referenced query: a -> a
+            var firstFragment = new FragmentBuilder<PromoExtend>("FirstFragment");
+            firstFragment.Fields(x => x.ProviderName);
+            firstFragment.AddFragment(x => x.Details.PromoImage.PromoExtend, firstFragment);
+
+            Assert.Equal(firstFragment.GetQuery().Query, expectedFistFragment);
+
+            //Cross-referenced: a -> b -> a
+            var secondFragment = new FragmentBuilder<PromoObject>("SecondFragment");
+            secondFragment.Fields(x => x.Url);
+
+            var thirdFragment = new FragmentBuilder<PromoExtend>("ThirdFragment");
+            thirdFragment.Fields(x => x.ProviderName);
+
+            secondFragment.AddFragment(x => x.PromoExtend, thirdFragment);
+            thirdFragment.AddFragment(x=> x.PromoExtend, secondFragment);
+
+            Assert.Equal(secondFragment.GetQuery().Query, expectedSecondFragmment);
+            Assert.Equal(thirdFragment.GetQuery().Query, expectedThirdFragmment);
+
+            GraphQueryBuilder graphQueryBuilder = new GraphQueryBuilder();
+            graphQueryBuilder
+                .OperationName("FragmentTest")
+                    .ForType<FragmentObject>()
+                        .Field(x => x.Name)
+                        .AddFragments(firstFragment, secondFragment)
+                    .ToQuery()
+                .BuildQueries();
+
+            Assert.Equal(graphQueryBuilder.GetFragments().First().GetQuery().Query, expectedFistFragment);
+            Assert.Equal(graphQueryBuilder.GetFragments().Skip(1).First().GetQuery().Query, expectedSecondFragmment);
+            Assert.Equal(graphQueryBuilder.GetFragments().Last().GetQuery().Query, expectedThirdFragmment);
+
+            //expect full query
+            Assert.Equal(expectedFullQuery, graphQueryBuilder.GetQuery().Query);
+        }
     }
 }