fix(#126): implicitly add db context to context graph

Author: jaredcnance

src/JsonApiDotNetCore/Builders/ContextGraphBuilder.cs

@@ -5,12 +5,13 @@
 using JsonApiDotNetCore.Internal;
 using JsonApiDotNetCore.Models;
 using JsonApiDotNetCore.Extensions;
+using System.Linq;
 
 namespace JsonApiDotNetCore.Builders
 {
     public class ContextGraphBuilder : IContextGraphBuilder
     {
-        private List<ContextEntity> _entities;
+        private List<ContextEntity> _entities = new List<ContextEntity>();
         private bool _usesDbContext;
         public Link DocumentLinks { get; set; } = Link.All;
 
@@ -32,6 +33,9 @@ public IContextGraph Build()
         public void AddResource<TResource>(string pluralizedTypeName) where TResource : class
         {
             var entityType = typeof(TResource);
+
+            VerifyEntityIsNotAlreadyDefined(entityType);
+
             _entities.Add(new ContextEntity
             {
                 EntityName = pluralizedTypeName,
@@ -98,8 +102,6 @@ public void AddDbContext<T>() where T : DbContext
 
             var contextType = typeof(T);
 
-            var entities = new List<ContextEntity>();
-
             var contextProperties = contextType.GetProperties();
 
             foreach (var property in contextProperties)
@@ -110,7 +112,10 @@ public void AddDbContext<T>() where T : DbContext
                     && dbSetType.GetGenericTypeDefinition() == typeof(DbSet<>))
                 {
                     var entityType = dbSetType.GetGenericArguments()[0];
-                    entities.Add(new ContextEntity
+                    
+                    VerifyEntityIsNotAlreadyDefined(entityType);
+
+                    _entities.Add(new ContextEntity
                     {
                         EntityName = GetResourceName(property),
                         EntityType = entityType,
@@ -119,8 +124,6 @@ public void AddDbContext<T>() where T : DbContext
                     });
                 }
             }
-
-            _entities = entities;
         }
 
         private string GetResourceName(PropertyInfo property)
@@ -131,5 +134,11 @@ private string GetResourceName(PropertyInfo property)
 
             return ((ResourceAttribute)resourceAttribute).ResourceName;
         }
+
+        private void VerifyEntityIsNotAlreadyDefined(Type entityType)
+        {
+            if (_entities.Any(e => e.EntityType == entityType))
+                throw new InvalidOperationException($"Cannot add entity type {entityType} to context graph, there is already an entity of that type configured.");
+        }
     }
 }

src/JsonApiDotNetCore/Configuration/JsonApiOptions.cs

@@ -13,31 +13,28 @@ public class JsonApiOptions
         public int DefaultPageSize { get; set; }
         public bool IncludeTotalRecordCount { get; set; }
         public bool AllowClientGeneratedIds { get; set; }
-        public IContextGraph ContextGraph  { get; set; }
-        public IContractResolver JsonContractResolver  { get; set; }  = new DasherizedResolver();
+        public IContextGraph ContextGraph { get; set; }
+        public IContractResolver JsonContractResolver { get; set; } = new DasherizedResolver();
+        internal IContextGraphBuilder ContextGraphBuilder { get; } = new ContextGraphBuilder();
 
         public void BuildContextGraph<TContext>(Action<IContextGraphBuilder> builder)
         where TContext : DbContext
         {
-            var contextGraphBuilder = new ContextGraphBuilder();
-            
-            contextGraphBuilder.AddDbContext<TContext>();
+            BuildContextGraph(builder);
 
-            builder?.Invoke(contextGraphBuilder);
+            ContextGraphBuilder.AddDbContext<TContext>();
 
-            ContextGraph = contextGraphBuilder.Build();
+            ContextGraph = ContextGraphBuilder.Build();
         }
 
         public void BuildContextGraph(Action<IContextGraphBuilder> builder)
         {
-            if(builder == null)
+            if (builder == null)
                 throw new ArgumentException("Cannot build non-EF context graph without an IContextGraphBuilder action", nameof(builder));
 
-            var contextGraphBuilder = new ContextGraphBuilder();
+            builder(ContextGraphBuilder);
 
-            builder(contextGraphBuilder);
-
-            ContextGraph = contextGraphBuilder.Build();
+            ContextGraph = ContextGraphBuilder.Build();
         }
     }
 }

src/JsonApiDotNetCore/Extensions/IServiceCollectionExtensions.cs

@@ -40,6 +40,8 @@ public static void AddJsonApi<TContext>(this IServiceCollection services,
 
             options(config);
 
+            config.BuildContextGraph(builder => builder.AddDbContext<TContext>());
+
             mvcBuilder
                 .AddMvcOptions(opt =>
                 {
@@ -83,7 +85,7 @@ public static void AddJsonApiInternals(
             this IServiceCollection services,
             JsonApiOptions jsonApiOptions)
         {
-            if(!jsonApiOptions.ContextGraph.UsesDbContext)
+            if (!jsonApiOptions.ContextGraph.UsesDbContext)
             {
                 services.AddScoped<DbContext>();
                 services.AddSingleton<DbContextOptions>(new DbContextOptionsBuilder().Options);

test/UnitTests/Builders/ContextGraphBuilder_Tests.cs

@@ -0,0 +1,42 @@
+using System;
+using JsonApiDotNetCore.Extensions;
+using JsonApiDotNetCore.Internal;
+using JsonApiDotNetCore.Models;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Moq;
+using Xunit;
+
+namespace UnitTests
+{
+    public class ContextGraphBuilder_Tests
+    {
+        class NonDbResource : Identifiable {}
+        class DbResource : Identifiable {}
+        class TestContext : DbContext {
+            public DbSet<DbResource> DbResources { get; set; }
+        }
+
+        [Fact]
+        public void Can_Build_ContextGraph_Using_Builder()
+        {
+            // arrange
+            var services = new ServiceCollection();
+            services.AddJsonApi<TestContext>(opt => {
+                opt.BuildContextGraph(b => {
+                    b.AddResource<NonDbResource>("non-db-resources");
+                });
+            });
+
+            // act
+            var container = services.BuildServiceProvider();
+
+            // assert
+            var contextGraph = container.GetRequiredService<IContextGraph>();
+            var dbResource = contextGraph.GetContextEntity("db-resources").EntityType;
+            var nonDbResource = contextGraph.GetContextEntity("non-db-resources").EntityType;
+            Assert.Equal(typeof(DbResource), dbResource);
+            Assert.Equal(typeof(NonDbResource), nonDbResource);
+        }
+    }
+}