NRT annotations (#23938)

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* Diagnostics
* Proxies
* Abstractions
* Analyzers

Part of #19007

Author: roji

src/EFCore.Abstractions/ChangeTracking/Internal/ObservableBackedBindingList.cs

@@ -18,8 +18,8 @@ namespace Microsoft.EntityFrameworkCore.ChangeTracking.Internal
     public class ObservableBackedBindingList<T> : SortableBindingList<T>
     {
         private bool _addingNewInstance;
-        private T _addNewInstance;
-        private T _cancelNewInstance;
+        private T? _addNewInstance;
+        private T? _cancelNewInstance;
 
         private readonly ICollection<T> _observableCollection;
         private bool _inCollectionChanged;
@@ -102,7 +102,7 @@ public override void EndNew(int itemIndex)
                 && itemIndex < Count
                 && Equals(base[itemIndex], _addNewInstance))
             {
-                AddToObservableCollection(_addNewInstance);
+                AddToObservableCollection(_addNewInstance!);
                 _addNewInstance = default;
                 _addingNewInstance = false;
             }
@@ -180,7 +180,7 @@ protected override void SetItem(int index, T item)
             }
         }
 
-        private void ObservableCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        private void ObservableCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
             // Don't try to change the binding list if the original change came from the binding list
             // and the ObservableCollection is just being changed to match it.
@@ -202,7 +202,7 @@ private void ObservableCollectionChanged(object sender, NotifyCollectionChangedE
                     if (e.Action == NotifyCollectionChangedAction.Remove
                         || e.Action == NotifyCollectionChangedAction.Replace)
                     {
-                        foreach (T entity in e.OldItems)
+                        foreach (T entity in e.OldItems!)
                         {
                             Remove(entity);
                         }
@@ -211,7 +211,7 @@ private void ObservableCollectionChanged(object sender, NotifyCollectionChangedE
                     if (e.Action == NotifyCollectionChangedAction.Add
                         || e.Action == NotifyCollectionChangedAction.Replace)
                     {
-                        foreach (T entity in e.NewItems)
+                        foreach (T entity in e.NewItems!)
                         {
                             Add(entity);
                         }

src/EFCore.Abstractions/ChangeTracking/Internal/SortableBindingList.cs

@@ -20,7 +20,7 @@ public class SortableBindingList<T> : BindingList<T>
     {
         private bool _isSorted;
         private ListSortDirection _sortDirection;
-        private PropertyDescriptor _sortProperty;
+        private PropertyDescriptor? _sortProperty;
 
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -87,7 +87,7 @@ protected override ListSortDirection SortDirectionCore
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        protected override PropertyDescriptor SortPropertyCore
+        protected override PropertyDescriptor? SortPropertyCore
             => _sortProperty;
 
         /// <summary>
@@ -115,12 +115,22 @@ public PropertyComparer(PropertyDescriptor prop, ListSortDirection direction)
                 _prop = prop;
                 _direction = direction;
 
-                var property = typeof(Comparer<>).MakeGenericType(prop.PropertyType).GetTypeInfo().GetDeclaredProperty("Default");
-                _comparer = (IComparer)property.GetValue(null, null);
+                var property = typeof(Comparer<>).MakeGenericType(prop.PropertyType).GetTypeInfo().GetDeclaredProperty("Default")!;
+                _comparer = (IComparer)property.GetValue(null, null)!;
             }
 
-            public override int Compare(T left, T right)
+            public override int Compare(T? left, T? right)
             {
+                if (left is null)
+                {
+                    return right is null ? 0 : -1;
+                }
+
+                if (right is null)
+                {
+                    return 1;
+                }
+
                 var leftValue = _prop.GetValue(left);
                 var rightValue = _prop.GetValue(right);
 

src/EFCore.Abstractions/ChangeTracking/ObservableCollectionListSource.cs

@@ -26,7 +26,7 @@ namespace Microsoft.EntityFrameworkCore.ChangeTracking
     public class ObservableCollectionListSource<T> : ObservableCollection<T>, IListSource
         where T : class
     {
-        private IBindingList _bindingList;
+        private IBindingList? _bindingList;
 
         /// <summary>
         ///     Initializes a new instance of the <see cref="ObservableCollectionListSource{T}" /> class.
@@ -70,6 +70,6 @@ bool IListSource.ContainsListCollection
         ///     An <see cref="IBindingList" /> in sync with the ObservableCollection.
         /// </returns>
         IList IListSource.GetList()
-            => _bindingList ?? (_bindingList = this.ToBindingList());
+            => _bindingList ??= this.ToBindingList();
     }
 }

src/EFCore.Abstractions/DbFunctionAttribute.cs

@@ -5,8 +5,6 @@
 using JetBrains.Annotations;
 using Microsoft.EntityFrameworkCore.Utilities;
 
-#nullable enable
-
 namespace Microsoft.EntityFrameworkCore
 {
     /// <summary>

src/EFCore.Abstractions/EFCore.Abstractions.csproj

@@ -7,6 +7,7 @@
     <AssemblyName>Microsoft.EntityFrameworkCore.Abstractions</AssemblyName>
     <RootNamespace>Microsoft.EntityFrameworkCore</RootNamespace>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/EFCore.Abstractions/EntityTypeConfigurationAttribute.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 using System;
+using Microsoft.EntityFrameworkCore.Utilities;
 
 namespace Microsoft.EntityFrameworkCore
 {
@@ -16,6 +17,8 @@ public sealed class EntityTypeConfigurationAttribute : Attribute
         /// <param name="entityConfigurationType"> The IEntityTypeConfiguration&lt;&gt; type to use. </param>
         public EntityTypeConfigurationAttribute(Type entityConfigurationType)
         {
+            Check.NotNull(entityConfigurationType, nameof(entityConfigurationType));
+
             EntityTypeConfigurationType = entityConfigurationType;
         }
 

src/EFCore.Abstractions/IndexAttribute.cs

@@ -6,6 +6,7 @@
 using System.Linq;
 using JetBrains.Annotations;
 using Microsoft.EntityFrameworkCore.Utilities;
+using CA = System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.EntityFrameworkCore
 {
@@ -16,13 +17,13 @@ namespace Microsoft.EntityFrameworkCore
     public sealed class IndexAttribute : Attribute
     {
         private bool? _isUnique;
-        private string _name;
+        private string? _name;
 
         /// <summary>
         ///     Initializes a new instance of the <see cref="IndexAttribute" /> class.
         /// </summary>
         /// <param name="propertyNames"> The properties which constitute the index, in order (there must be at least one). </param>
-        public IndexAttribute([CanBeNull] params string[] propertyNames)
+        public IndexAttribute([NotNull] params string[] propertyNames)
         {
             Check.NotEmpty(propertyNames, nameof(propertyNames));
             Check.HasNoEmptyElements(propertyNames, nameof(propertyNames));
@@ -38,7 +39,8 @@ public IndexAttribute([CanBeNull] params string[] propertyNames)
         /// <summary>
         ///     The name of the index.
         /// </summary>
-        public string Name
+        [CA.DisallowNull]
+        public string? Name
         {
             get => _name;
             [param: NotNull] set => _name = Check.NotNull(value, nameof(value));

src/EFCore.Abstractions/Infrastructure/ILazyLoader.cs

@@ -40,7 +40,7 @@ void SetLoaded(
         /// </summary>
         /// <param name="entity"> The entity on which the navigation property is located. </param>
         /// <param name="navigationName"> The navigation property name. </param>
-        void Load([NotNull] object entity, [NotNull] [CallerMemberName] string navigationName = null);
+        void Load([NotNull] object entity, [NotNull] [CallerMemberName] string navigationName = "");
 
         /// <summary>
         ///     Loads a navigation property if it has not already been loaded.
@@ -55,6 +55,6 @@ Task LoadAsync(
 #pragma warning restore CA1068 // CancellationToken parameters must come last
             [NotNull] object entity,
             CancellationToken cancellationToken = default,
-            [NotNull] [CallerMemberName] string navigationName = null);
+            [NotNull] [CallerMemberName] string navigationName = "");
     }
 }

src/EFCore.Abstractions/Infrastructure/LazyLoaderExtensions.cs

@@ -23,15 +23,13 @@ public static class LazyLoaderExtensions
         /// <returns>
         ///     The loaded navigation property value, or the navigation property value unchanged if the loader is <see langword="null" />.
         /// </returns>
-        public static TRelated Load<TRelated>(
-            [CanBeNull] this ILazyLoader loader,
+        public static TRelated? Load<TRelated>(
+            [CanBeNull] this ILazyLoader? loader,
             [NotNull] object entity,
-            [CanBeNull] ref TRelated navigationField,
-            // ReSharper disable once AssignNullToNotNullAttribute
-            [NotNull] [CallerMemberName] string navigationName = null)
+            [CanBeNull] ref TRelated? navigationField,
+            [NotNull] [CallerMemberName] string navigationName = "")
             where TRelated : class
         {
-            // ReSharper disable once AssignNullToNotNullAttribute
             loader?.Load(entity, navigationName);
 
             return navigationField;

src/EFCore.Abstractions/Query/NotParameterizedAttribute.cs

@@ -3,8 +3,6 @@
 
 using System;
 
-#nullable enable
-
 namespace Microsoft.EntityFrameworkCore.Query
 {
     /// <summary>