Restructured eager loading tests and fixed two bugs (#882)

* Restructured eager loading tests and fixed two bugs:
1] During update, eager loads without parse fieldsets were not loaded at all places, which would make the resource change tracker incorrectly detect changes and return 200 instead of 204.
2] Creating a resource with a required EagerLoad (not exposed as relationship) was not possible, as there was no place for user code to create the related entity. Fixed this by making the create logic more similar to update logic. The change tracker scans through the initally created resource, invoking all property getters, enabling them to create related entities on the fly. See usage in Building.cs.

* Updated test to set calculated property that depends on required relationship

* Improved handling for non-loaded related entities.

Yesterday I was trying to solve the wrong problem. The problem is not how to prevent a crash when creating a new resource that has a required EagerLoad relationship. Instead, the problem is that api developers need a way to assign relationships (EagerLoads or not) on resource creation. Whether such a relationship is required or not is irrelevant, it depends on business logic which relationships must be assigned. And that may be an already-existing entity or a new one. If the goal is to assign an already-existing entity, the api developer needs an async method to load that entity and assign it to the resource being created.

This commit adds `IResourceWriteRepository.GetForCreateAsync`, which is analog to `GetForUpdateAsync`. This makes the resource creation logic in resource service very similar to update.

This also fixes the tests, where [NotMapped] was missing on calculated properties. Except for request body deserialization, there is no more need to handle nulls in calculated properties that access a required related EagerLoad entity. And by treating the deserialized resource object just as an input source (which is never saved), we get by with just storing the deserialized data for later use, knowing it will be read and copied into the resource instance we're going to save.

Also reordered repository members in a more logical order (used to be verb-based).

Author: Bart Koelman

src/Examples/JsonApiDotNetCoreExample/Controllers/VisasController.cs

@@ -11,7 +11,6 @@ public sealed class AppDbContext : DbContext
 
         public DbSet<TodoItem> TodoItems { get; set; }
         public DbSet<Passport> Passports { get; set; }
-        public DbSet<Visa> Visas { get; set; }
         public DbSet<Person> People { get; set; }
         public DbSet<TodoItemCollection> TodoItemCollections { get; set; }
         public DbSet<KebabCasedModel> KebabCasedModels { get; set; }
@@ -69,11 +68,6 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
                 .HasForeignKey<Person>("PassportKey")
                 .OnDelete(DeleteBehavior.SetNull);
 
-            modelBuilder.Entity<Passport>()
-                .HasMany(passport => passport.GrantedVisas)
-                .WithOne()
-                .OnDelete(DeleteBehavior.Cascade);
-
             modelBuilder.Entity<TodoItem>()
                 .HasOne(p => p.OneToOnePerson)
                 .WithOne(p => p.OneToOneTodoItem)

src/Examples/JsonApiDotNetCoreExample/Data/AppDbContext.cs

@@ -52,15 +52,6 @@ public string BirthCountryName
         [EagerLoad]
         public Country BirthCountry { get; set; }
 
-        [Attr(Capabilities = AttrCapabilities.All & ~(AttrCapabilities.AllowCreate | AttrCapabilities.AllowChange))]
-        [NotMapped]
-        public string GrantedVisaCountries => GrantedVisas == null || !GrantedVisas.Any()
-            ? null
-            : string.Join(", ", GrantedVisas.Select(v => v.TargetCountry.Name));
-
-        [EagerLoad]
-        public ICollection<Visa> GrantedVisas { get; set; }
-
         public Passport(AppDbContext appDbContext)
         {
             _systemClock = appDbContext.SystemClock;

src/Examples/JsonApiDotNetCoreExample/Models/Passport.cs

@@ -21,7 +21,7 @@ public class QueryLayerComposer : IQueryLayerComposer
         public QueryLayerComposer(
             IEnumerable<IQueryConstraintProvider> constraintProviders,
             IResourceContextProvider resourceContextProvider,
-            IResourceDefinitionAccessor resourceDefinitionAccessor, 
+            IResourceDefinitionAccessor resourceDefinitionAccessor,
             IJsonApiOptions options,
             IPaginationContext paginationContext,
             ITargetedFields targetedFields)
@@ -93,7 +93,8 @@ private IncludeExpression ComposeChildren(QueryLayer topLayer, ICollection<Expre
         {
             var include = constraints
                 .Where(constraint => constraint.Scope == null)
-                .Select(constraint => constraint.Expression).OfType<IncludeExpression>()
+                .Select(constraint => constraint.Expression)
+                .OfType<IncludeExpression>()
                 .FirstOrDefault() ?? IncludeExpression.Empty;
 
             var includeElements =
@@ -104,7 +105,7 @@ private IncludeExpression ComposeChildren(QueryLayer topLayer, ICollection<Expre
                 : include;
         }
 
-        private IReadOnlyCollection<IncludeElementExpression> ProcessIncludeSet(IReadOnlyCollection<IncludeElementExpression> includeElements, 
+        private IReadOnlyCollection<IncludeElementExpression> ProcessIncludeSet(IReadOnlyCollection<IncludeElementExpression> includeElements,
             QueryLayer parentLayer, ICollection<RelationshipAttribute> parentRelationshipChain, ICollection<ExpressionInScope> constraints)
         {
             includeElements = GetIncludeElements(includeElements, parentLayer.ResourceContext) ?? Array.Empty<IncludeElementExpression>();
@@ -135,7 +136,7 @@ private IReadOnlyCollection<IncludeElementExpression> ProcessIncludeSet(IReadOnl
                     {
                         Filter = GetFilter(expressionsInCurrentScope, resourceContext),
                         Sort = GetSort(expressionsInCurrentScope, resourceContext),
-                        Pagination = ((JsonApiOptions) _options).DisableChildrenPagination
+                        Pagination = ((JsonApiOptions)_options).DisableChildrenPagination
                             ? null
                             : GetPagination(expressionsInCurrentScope, resourceContext),
                         Projection = GetSparseFieldSetProjection(expressionsInCurrentScope, resourceContext)
@@ -186,7 +187,10 @@ public QueryLayer ComposeForGetById<TId>(TId id, ResourceContext resourceContext
 
             if (fieldSelection == TopFieldSelection.OnlyIdAttribute)
             {
-                queryLayer.Projection = new Dictionary<ResourceFieldAttribute, QueryLayer> {{idAttribute, null}};
+                queryLayer.Projection = new Dictionary<ResourceFieldAttribute, QueryLayer>
+                {
+                    [idAttribute] = null
+                };
             }
             else if (fieldSelection == TopFieldSelection.WithAllAttributes && queryLayer.Projection != null)
             {
@@ -234,9 +238,9 @@ public QueryLayer WrapLayerForSecondaryEndpoint<TId>(QueryLayer secondaryLayer,
             secondaryLayer.Include = null;
 
             var primaryIdAttribute = GetIdAttribute(primaryResourceContext);
-            var sparseFieldSet = new SparseFieldSetExpression(new[] { primaryIdAttribute });
+            var sparseFieldSet = new SparseFieldSetExpression(new[] {primaryIdAttribute});
 
-            var primaryProjection = GetSparseFieldSetProjection(new[] { sparseFieldSet }, primaryResourceContext) ?? new Dictionary<ResourceFieldAttribute, QueryLayer>();
+            var primaryProjection = GetSparseFieldSetProjection(new[] {sparseFieldSet}, primaryResourceContext) ?? new Dictionary<ResourceFieldAttribute, QueryLayer>();
             primaryProjection[secondaryRelationship] = secondaryLayer;
             primaryProjection[primaryIdAttribute] = null;
 
@@ -276,10 +280,10 @@ private FilterExpression CreateFilterByIds<TId>(ICollection<TId> ids, AttrAttrib
                 filter = new EqualsAnyOfExpression(idChain, constants);
             }
 
-            return filter == null 
-                ? existingFilter 
-                : existingFilter == null 
-                    ? filter 
+            return filter == null
+                ? existingFilter
+                : existingFilter == null
+                    ? filter
                     : new LogicalExpression(LogicalOperator.And, new[] {filter, existingFilter});
         }
 
@@ -294,7 +298,7 @@ public QueryLayer ComposeForUpdate<TId>(TId id, ResourceContext primaryResource)
             var primaryIdAttribute = GetIdAttribute(primaryResource);
 
             var primaryLayer = ComposeTopLayer(Array.Empty<ExpressionInScope>(), primaryResource);
-            primaryLayer.Include = includeElements.Any() ? new IncludeExpression(includeElements) : null;
+            primaryLayer.Include = includeElements.Any() ? new IncludeExpression(includeElements) : IncludeExpression.Empty;
             primaryLayer.Sort = null;
             primaryLayer.Pagination = null;
             primaryLayer.Filter = CreateFilterByIds(new[] {id}, primaryIdAttribute, primaryLayer.Filter);
@@ -332,6 +336,7 @@ public QueryLayer ComposeForGetRelationshipRightIds(RelationshipAttribute relati
 
             return new QueryLayer(rightResourceContext)
             {
+                Include = IncludeExpression.Empty,
                 Filter = filter,
                 Projection = new Dictionary<ResourceFieldAttribute, QueryLayer>
                 {
@@ -386,10 +391,12 @@ protected virtual FilterExpression GetFilter(IReadOnlyCollection<QueryExpression
             if (resourceContext == null) throw new ArgumentNullException(nameof(resourceContext));
 
             var filters = expressionsInScope.OfType<FilterExpression>().ToArray();
-            var filter = filters.Length > 1 ? new LogicalExpression(LogicalOperator.And, filters) : filters.FirstOrDefault();
 
-            filter = _resourceDefinitionAccessor.OnApplyFilter(resourceContext.ResourceType, filter);
-            return filter;
+            var filter = filters.Length > 1
+                ? new LogicalExpression(LogicalOperator.And, filters)
+                : filters.FirstOrDefault();
+
+            return _resourceDefinitionAccessor.OnApplyFilter(resourceContext.ResourceType, filter);
         }
 
         protected virtual SortExpression GetSort(IReadOnlyCollection<QueryExpression> expressionsInScope, ResourceContext resourceContext)
@@ -398,7 +405,7 @@ protected virtual SortExpression GetSort(IReadOnlyCollection<QueryExpression> ex
             if (resourceContext == null) throw new ArgumentNullException(nameof(resourceContext));
 
             var sort = expressionsInScope.OfType<SortExpression>().FirstOrDefault();
-            
+
             sort = _resourceDefinitionAccessor.OnApplySort(resourceContext.ResourceType, sort);
 
             if (sort == null)
@@ -416,7 +423,7 @@ protected virtual PaginationExpression GetPagination(IReadOnlyCollection<QueryEx
             if (resourceContext == null) throw new ArgumentNullException(nameof(resourceContext));
 
             var pagination = expressionsInScope.OfType<PaginationExpression>().FirstOrDefault();
-            
+
             pagination = _resourceDefinitionAccessor.OnApplyPagination(resourceContext.ResourceType, pagination);
 
             pagination ??= new PaginationExpression(PageNumber.ValueOne, _options.DefaultPageSize);
@@ -444,7 +451,7 @@ protected virtual IDictionary<ResourceFieldAttribute, QueryLayer> GetSparseField
             var idAttribute = GetIdAttribute(resourceContext);
             attributes.Add(idAttribute);
 
-            return attributes.Cast<ResourceFieldAttribute>().ToDictionary(key => key, value => (QueryLayer) null);
+            return attributes.Cast<ResourceFieldAttribute>().ToDictionary(key => key, value => (QueryLayer)null);
         }
 
         private static AttrAttribute GetIdAttribute(ResourceContext resourceContext)