Change tracking for patch updates, to improve json:api spec compliance (#704)

Change tracking for patch updates, to improve json:api spec compliance

I have added some calculated properties to the examples, in order to have tests for:
- nothing outside the patch request changed (returns empty data)
  - `KebabCaseFormatterTests.KebabCaseFormatter_Update_IsUpdated` has no side effects in updating `KebabCasedModel` attributes
  - `ManyToManyTests.Can_Update_Many_To_Many` has no side effects in updating `Article` tags
  - `ManyToManyTests.Can_Update_Many_To_Many_With_Complete_Replacement` has no side effects in updating `Article` tags
  - `ManyToManyTests.Can_Update_Many_To_Many_With_Complete_Replacement_With_Overlap` has no side effects in updating `Article` tags
- exposed attribute that was not in PATCH request changed (returns attributes)
  - `UpdatingDataTests.PatchResource_ModelWithEntityFrameworkInheritance_IsPatched` updates `User.Password` property, which updates exposed `LastPasswordChange` attribute
  - `UpdatingDataTests.Patch_Entity_With_HasMany_Does_Not_Include_Relationships` updates `Person.FirstName` property, which updates exposed `Initials` attribute
  - `TodoItemsControllerTests.Can_Patch_TodoItemWithNullable` does not update exposed `TodoItem.AlwaysChangingValue` attribute
- exposed attribute that was in PATCH request changed (returns attributes)
  - `TodoItemsControllerTests.Can_Patch_TodoItem` updates `TodoItem.AlwaysChangingValue` attribute

Also updated a few places where an empty list was allocated each time with a cached empty array instance.

Author: Bart Koelman

src/Examples/JsonApiDotNetCoreExample/Models/Passport.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
@@ -7,8 +8,24 @@ namespace JsonApiDotNetCoreExample.Models
 {
     public class Passport : Identifiable
     {
+        private int? _socialSecurityNumber;
+
+        [Attr]
+        public int? SocialSecurityNumber
+        {
+            get => _socialSecurityNumber;
+            set
+            {
+                if (value != _socialSecurityNumber)
+                {
+                    LastSocialSecurityNumberChange = DateTime.Now;
+                    _socialSecurityNumber = value;
+                }
+            }
+        }
+
         [Attr]
-        public int? SocialSecurityNumber { get; set; }
+        public DateTime LastSocialSecurityNumberChange { get; set; }
 
         [Attr]
         public bool IsLocked { get; set; }

src/Examples/JsonApiDotNetCoreExample/Models/Person.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using JsonApiDotNetCore.Models;
 using JsonApiDotNetCore.Models.Links;
 
@@ -12,10 +13,26 @@ public sealed class PersonRole : Identifiable
 
     public sealed class Person : Identifiable, IIsLockable
     {
+        private string _firstName;
+
         public bool IsLocked { get; set; }
 
         [Attr]
-        public string FirstName { get; set; }
+        public string FirstName
+        {
+            get => _firstName;
+            set
+            {
+                if (value != _firstName)
+                {
+                    _firstName = value;
+                    Initials = string.Concat(value.Split(' ').Select(x => char.ToUpperInvariant(x[0])));
+                }
+            }
+        }
+
+        [Attr]
+        public string Initials { get; set; }
 
         [Attr]
         public string LastName { get; set; }

src/Examples/JsonApiDotNetCoreExample/Models/TodoItem.cs

@@ -22,6 +22,13 @@ public TodoItem()
         [Attr]
         public Guid GuidProperty { get; set; }
 
+        [Attr]
+        public string AlwaysChangingValue
+        {
+            get => Guid.NewGuid().ToString();
+            set { }
+        }
+
         [Attr]
         public DateTime CreatedDate { get; set; }
 

src/Examples/JsonApiDotNetCoreExample/Models/User.cs

@@ -1,11 +1,29 @@
+using System;
 using JsonApiDotNetCore.Models;
 
 namespace JsonApiDotNetCoreExample.Models
 {
     public class User : Identifiable
     {
+        private string _password;
+
         [Attr] public string Username { get; set; }
-        [Attr] public string Password { get; set; }
+
+        [Attr]
+        public string Password
+        {
+            get => _password;
+            set
+            {
+                if (value != _password)
+                {
+                    _password = value;
+                    LastPasswordChange = DateTime.Now;
+                }
+            }
+        }
+
+        [Attr] public DateTime LastPasswordChange { get; set; }
     }
 
     public sealed class SuperUser : User

src/Examples/JsonApiDotNetCoreExample/Services/CustomArticleService.cs

@@ -8,6 +8,7 @@
 using Microsoft.Extensions.Logging;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using JsonApiDotNetCore.RequestServices;
 
 namespace JsonApiDotNetCoreExample.Services
 {
@@ -19,8 +20,9 @@ public CustomArticleService(
             ILoggerFactory loggerFactory,
             IResourceRepository<Article, int> repository,
             IResourceContextProvider provider,
+            IResourceChangeTracker<Article> resourceChangeTracker,
             IResourceHookExecutor hookExecutor = null)
-            : base(queryParameters, options, loggerFactory, repository, provider, hookExecutor)
+            : base(queryParameters, options, loggerFactory, repository, provider, resourceChangeTracker, hookExecutor)
         { }
 
         public override async Task<Article> GetAsync(int id)

src/JsonApiDotNetCore/Builders/JsonApiApplicationBuilder.cs

@@ -21,6 +21,7 @@
 using JsonApiDotNetCore.Serialization.Server;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using JsonApiDotNetCore.QueryParameterServices.Common;
+using JsonApiDotNetCore.RequestServices;
 
 namespace JsonApiDotNetCore.Builders
 {
@@ -161,6 +162,7 @@ public void ConfigureServices()
             _services.AddScoped<ITargetedFields, TargetedFields>();
             _services.AddScoped<IResourceDefinitionProvider, ResourceDefinitionProvider>();
             _services.AddScoped<IFieldsToSerialize, FieldsToSerialize>();
+            _services.AddScoped(typeof(IResourceChangeTracker<>), typeof(DefaultResourceChangeTracker<>));
             _services.AddScoped<IQueryParameterActionFilter, QueryParameterActionFilter>();
 
             AddServerSerialization();

src/JsonApiDotNetCore/Controllers/BaseJsonApiController.cs

@@ -133,7 +133,7 @@ public virtual async Task<IActionResult> PatchAsync(TId id, [FromBody] T entity)
                 throw new InvalidModelStateException(ModelState, typeof(T), _jsonApiOptions.IncludeExceptionStackTraceInErrors);
 
             var updatedEntity = await _update.UpdateAsync(id, entity);
-            return Ok(updatedEntity);
+            return updatedEntity == null ? Ok(null) : Ok(updatedEntity);
         }
 
         public virtual async Task<IActionResult> PatchRelationshipsAsync(TId id, string relationshipName, [FromBody] object relationships)

src/JsonApiDotNetCore/Data/DefaultResourceRepository.cs

@@ -195,16 +195,12 @@ private void DetachRelationships(TResource entity)
         }
 
         /// <inheritdoc />
-        public virtual async Task<TResource> UpdateAsync(TResource updatedEntity)
+        public virtual async Task UpdateAsync(TResource requestEntity, TResource databaseEntity)
         {
-            _logger.LogTrace($"Entering {nameof(UpdateAsync)}({(updatedEntity == null ? "null" : "object")}).");
-
-            var databaseEntity = await Get(updatedEntity.Id).FirstOrDefaultAsync();
-            if (databaseEntity == null)
-                return null;
+            _logger.LogTrace($"Entering {nameof(UpdateAsync)}({(requestEntity == null ? "null" : "object")}, {(databaseEntity == null ? "null" : "object")}).");
 
             foreach (var attribute in _targetedFields.Attributes)
-                attribute.SetValue(databaseEntity, attribute.GetValue(updatedEntity));
+                attribute.SetValue(databaseEntity, attribute.GetValue(requestEntity));
 
             foreach (var relationshipAttr in _targetedFields.Relationships)
             {
@@ -213,7 +209,7 @@ public virtual async Task<TResource> UpdateAsync(TResource updatedEntity)
                 // trackedRelationshipValue is either equal to updatedPerson.todoItems,
                 // or replaced with the same set (same ids) of todoItems from the EF Core change tracker,
                 // which is the case if they were already tracked
-                object trackedRelationshipValue = GetTrackedRelationshipValue(relationshipAttr, updatedEntity, out _);
+                object trackedRelationshipValue = GetTrackedRelationshipValue(relationshipAttr, requestEntity, out _);
                 // loads into the db context any persons currently related
                 // to the todoItems in trackedRelationshipValue
                 LoadInverseRelationships(trackedRelationshipValue, relationshipAttr);
@@ -223,7 +219,6 @@ public virtual async Task<TResource> UpdateAsync(TResource updatedEntity)
             }
 
             await _context.SaveChangesAsync();
-            return databaseEntity;
         }
 
         /// <summary>
@@ -303,6 +298,13 @@ public virtual async Task<bool> DeleteAsync(TId id)
             return true;
         }
 
+        public virtual void FlushFromCache(TResource entity)
+        {
+            _logger.LogTrace($"Entering {nameof(FlushFromCache)}({nameof(entity)}).");
+
+            _context.Entry(entity).State = EntityState.Detached;
+        }
+
         private IQueryable<TResource> EagerLoad(IQueryable<TResource> entities, IEnumerable<EagerLoadAttribute> attributes, string chainPrefix = null)
         {
             foreach (var attribute in attributes)

src/JsonApiDotNetCore/Data/IResourceWriteRepository.cs

@@ -14,10 +14,12 @@ public interface IResourceWriteRepository<TResource, in TId>
     {
         Task<TResource> CreateAsync(TResource entity);
 
-        Task<TResource> UpdateAsync(TResource entity);
+        Task UpdateAsync(TResource requestEntity, TResource databaseEntity);
 
         Task UpdateRelationshipsAsync(object parent, RelationshipAttribute relationship, IEnumerable<string> relationshipIds);
 
         Task<bool> DeleteAsync(TId id);
+
+        void FlushFromCache(TResource entity);
     }
 }

src/JsonApiDotNetCore/Middleware/DefaultTypeMatchFilter.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Linq;
 using System.Net.Http;
 using JsonApiDotNetCore.Exceptions;