Make required dependent columns in shared table non-nullable.

src/EFCore.Design/Migrations/Design/CSharpSnapshotGenerator.cs

@@ -137,6 +137,16 @@ protected virtual void GenerateEntityTypes(
 
                 GenerateEntityTypeRelationships(builderName, entityType, stringBuilder);
             }
+
+            foreach (var entityType in entityTypes.Where(
+                e => !e.HasDefiningNavigation()
+                     && e.FindOwnership() == null
+                     && e.GetDeclaredNavigations().Any(n => !n.IsOnDependent && !n.ForeignKey.IsOwnership)))
+            {
+                stringBuilder.AppendLine();
+
+                GenerateEntityTypeNavigations(builderName, entityType, stringBuilder);
+            }
         }
 
         /// <summary>
@@ -215,6 +225,9 @@ protected virtual void GenerateEntityType(
                     if (ownerNavigation != null)
                     {
                         GenerateRelationships(builderName, entityType, stringBuilder);
+
+                        GenerateNavigations(builderName, entityType.GetDeclaredNavigations()
+                            .Where(n => !n.IsOnDependent && !n.ForeignKey.IsOwnership), stringBuilder);
                     }
 
                     GenerateData(builderName, entityType.GetProperties(), entityType.GetSeedData(providerValues: true), stringBuilder);
@@ -318,6 +331,9 @@ protected virtual void GenerateRelationships(
             GenerateForeignKeys(builderName, entityType.GetDeclaredForeignKeys(), stringBuilder);
 
             GenerateOwnedTypes(builderName, entityType.GetDeclaredReferencingForeignKeys().Where(fk => fk.IsOwnership), stringBuilder);
+
+            GenerateNavigations(builderName, entityType.GetDeclaredNavigations()
+                .Where(n => n.IsOnDependent || (!n.IsOnDependent && n.ForeignKey.IsOwnership)), stringBuilder);
         }
 
         /// <summary>
@@ -1188,6 +1204,128 @@ protected virtual void GenerateForeignKeyAnnotations(
             GenerateAnnotations(annotations.Values, stringBuilder);
         }
 
+        /// <summary>
+        ///     Generates code for the navigations of an <see cref="IEntityType" />.
+        /// </summary>
+        /// <param name="builderName"> The name of the builder variable. </param>
+        /// <param name="entityType"> The entity type. </param>
+        /// <param name="stringBuilder"> The builder code is added to. </param>
+        protected virtual void GenerateEntityTypeNavigations(
+            [NotNull] string builderName,
+            [NotNull] IEntityType entityType,
+            [NotNull] IndentedStringBuilder stringBuilder)
+        {
+            Check.NotEmpty(builderName, nameof(builderName));
+            Check.NotNull(entityType, nameof(entityType));
+            Check.NotNull(stringBuilder, nameof(stringBuilder));
+
+            stringBuilder
+                .Append(builderName)
+                .Append(".Entity(")
+                .Append(Code.Literal(entityType.Name))
+                .AppendLine(", b =>");
+
+            using (stringBuilder.Indent())
+            {
+                stringBuilder.Append("{");
+
+                using (stringBuilder.Indent())
+                {
+                    GenerateNavigations("b", entityType.GetDeclaredNavigations()
+                        .Where(n => !n.IsOnDependent && !n.ForeignKey.IsOwnership), stringBuilder);
+                }
+
+                stringBuilder.AppendLine("});");
+            }
+        }
+
+        /// <summary>
+        ///     Generates code for <see cref="INavigation" /> objects.
+        /// </summary>
+        /// <param name="builderName"> The name of the builder variable. </param>
+        /// <param name="navigations"> The navigations. </param>
+        /// <param name="stringBuilder"> The builder code is added to. </param>
+        protected virtual void GenerateNavigations(
+            [NotNull] string builderName,
+            [NotNull] IEnumerable<INavigation> navigations,
+            [NotNull] IndentedStringBuilder stringBuilder)
+        {
+            Check.NotNull(builderName, nameof(builderName));
+            Check.NotNull(navigations, nameof(navigations));
+            Check.NotNull(stringBuilder, nameof(stringBuilder));
+
+            foreach (var navigation in navigations)
+            {
+                stringBuilder.AppendLine();
+
+                GenerateNavigation(builderName, navigation, stringBuilder);
+            }
+        }
+
+        /// <summary>
+        ///     Generates code for an <see cref="INavigation" />.
+        /// </summary>
+        /// <param name="builderName"> The name of the builder variable. </param>
+        /// <param name="navigation"> The navigation. </param>
+        /// <param name="stringBuilder"> The builder code is added to. </param>
+        protected virtual void GenerateNavigation(
+            [NotNull] string builderName,
+            [NotNull] INavigation navigation,
+            [NotNull] IndentedStringBuilder stringBuilder)
+        {
+            Check.NotNull(builderName, nameof(builderName));
+            Check.NotNull(navigation, nameof(navigation));
+            Check.NotNull(stringBuilder, nameof(stringBuilder));
+
+            stringBuilder
+                .Append(builderName)
+                .Append(".Navigation(")
+                .Append(Code.Literal(navigation.Name))
+                .Append(")");
+
+            using (stringBuilder.Indent())
+            {
+                if (!navigation.IsOnDependent
+                    && !navigation.IsCollection
+                    && navigation.ForeignKey.IsRequiredDependent)
+                {
+                    stringBuilder
+                        .AppendLine()
+                        .Append(".IsRequired()");
+                }
+
+                GenerateNavigationAnnotations(navigation, stringBuilder);
+            }
+
+            stringBuilder.AppendLine(";");
+        }
+
+        /// <summary>
+        ///     Generates code for the annotations on a navigation.
+        /// </summary>
+        /// <param name="navigation"> The navigation. </param>
+        /// <param name="stringBuilder"> The builder code is added to. </param>
+        protected virtual void GenerateNavigationAnnotations(
+            [NotNull] INavigation navigation, [NotNull] IndentedStringBuilder stringBuilder)
+        {
+            Check.NotNull(navigation, nameof(navigation));
+            Check.NotNull(stringBuilder, nameof(stringBuilder));
+
+            var annotations = Dependencies.AnnotationCodeGenerator
+                .FilterIgnoredAnnotations(navigation.GetAnnotations())
+                .ToDictionary(a => a.Name, a => a);
+
+            foreach (var methodCallCodeFragment in
+                Dependencies.AnnotationCodeGenerator.GenerateFluentApiCalls(navigation, annotations))
+            {
+                stringBuilder
+                    .AppendLine()
+                    .Append(Code.Fragment(methodCallCodeFragment));
+            }
+
+            GenerateAnnotations(annotations.Values, stringBuilder);
+        }
+
         /// <summary>
         ///     Generates code for annotations.
         /// </summary>

src/EFCore.Design/Scaffolding/Internal/CSharpEntityTypeGenerator.cs

@@ -10,7 +10,6 @@
 using Microsoft.EntityFrameworkCore.Design;
 using Microsoft.EntityFrameworkCore.Design.Internal;
 using Microsoft.EntityFrameworkCore.Infrastructure;
-using Microsoft.EntityFrameworkCore.Internal;
 using Microsoft.EntityFrameworkCore.Metadata;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.Utilities;

src/EFCore.Relational/Design/AnnotationCodeGenerator.cs

@@ -214,15 +214,37 @@ public virtual IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
 
         /// <inheritdoc />
         public virtual IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
-            IForeignKey foreignKey, IDictionary<string, IAnnotation> annotations)
+            IForeignKey navigation, IDictionary<string, IAnnotation> annotations)
         {
             var methodCallCodeFragments = new List<MethodCallCodeFragment>();
 
             GenerateSimpleFluentApiCall(
                 annotations,
                 RelationalAnnotationNames.Name, nameof(RelationalForeignKeyBuilderExtensions.HasConstraintName), methodCallCodeFragments);
 
-            methodCallCodeFragments.AddRange(GenerateFluentApiCallsHelper(foreignKey, annotations, GenerateFluentApi));
+            methodCallCodeFragments.AddRange(GenerateFluentApiCallsHelper(navigation, annotations, GenerateFluentApi));
+
+            return methodCallCodeFragments;
+        }
+
+        /// <inheritdoc />
+        public virtual IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
+            INavigation navigation, IDictionary<string, IAnnotation> annotations)
+        {
+            var methodCallCodeFragments = new List<MethodCallCodeFragment>();
+
+            methodCallCodeFragments.AddRange(GenerateFluentApiCallsHelper(navigation, annotations, GenerateFluentApi));
+
+            return methodCallCodeFragments;
+        }
+
+        /// <inheritdoc />
+        public virtual IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
+            ISkipNavigation navigation, IDictionary<string, IAnnotation> annotations)
+        {
+            var methodCallCodeFragments = new List<MethodCallCodeFragment>();
+
+            methodCallCodeFragments.AddRange(GenerateFluentApiCallsHelper(navigation, annotations, GenerateFluentApi));
 
             return methodCallCodeFragments;
         }
@@ -501,6 +523,46 @@ protected virtual MethodCallCodeFragment GenerateFluentApi([NotNull] IForeignKey
             return null;
         }
 
+        /// <summary>
+        ///     <para>
+        ///         Returns a fluent API call for the given <paramref name="annotation" />, or <see langword="null" />
+        ///         if no fluent API call exists for it.
+        ///     </para>
+        ///     <para>
+        ///         The default implementation always returns <see langword="null" />.
+        ///     </para>
+        /// </summary>
+        /// <param name="navigation"> The <see cref="INavigation" />. </param>
+        /// <param name="annotation"> The <see cref="IAnnotation" />. </param>
+        /// <returns> <see langword="null" />. </returns>
+        protected virtual MethodCallCodeFragment GenerateFluentApi([NotNull] INavigation navigation, [NotNull] IAnnotation annotation)
+        {
+            Check.NotNull(navigation, nameof(navigation));
+            Check.NotNull(annotation, nameof(annotation));
+
+            return null;
+        }
+
+        /// <summary>
+        ///     <para>
+        ///         Returns a fluent API call for the given <paramref name="annotation" />, or <see langword="null" />
+        ///         if no fluent API call exists for it.
+        ///     </para>
+        ///     <para>
+        ///         The default implementation always returns <see langword="null" />.
+        ///     </para>
+        /// </summary>
+        /// <param name="navigation"> The <see cref="ISkipNavigation" />. </param>
+        /// <param name="annotation"> The <see cref="IAnnotation" />. </param>
+        /// <returns> <see langword="null" />. </returns>
+        protected virtual MethodCallCodeFragment GenerateFluentApi([NotNull] ISkipNavigation navigation, [NotNull] IAnnotation annotation)
+        {
+            Check.NotNull(navigation, nameof(navigation));
+            Check.NotNull(annotation, nameof(annotation));
+
+            return null;
+        }
+
         /// <summary>
         ///     <para>
         ///         Returns a fluent API call for the given <paramref name="annotation" />, or <see langword="null" />

src/EFCore.Relational/Design/IAnnotationCodeGenerator.cs

@@ -121,6 +121,26 @@ IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
             [NotNull] IForeignKey foreignKey, [NotNull] IDictionary<string, IAnnotation> annotations)
             => Array.Empty<MethodCallCodeFragment>();
 
+        /// <summary>
+        ///     For the given annotations which have corresponding fluent API calls, returns those fluent API calls
+        ///     and removes the annotations.
+        /// </summary>
+        /// <param name="navigation"> The navigation to which the annotations are applied. </param>
+        /// <param name="annotations"> The set of annotations from which to generate fluent API calls. </param>
+        IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
+            [NotNull] INavigation navigation, [NotNull] IDictionary<string, IAnnotation> annotations)
+            => Array.Empty<MethodCallCodeFragment>();
+
+        /// <summary>
+        ///     For the given annotations which have corresponding fluent API calls, returns those fluent API calls
+        ///     and removes the annotations.
+        /// </summary>
+        /// <param name="navigation"> The skip navigation to which the annotations are applied. </param>
+        /// <param name="annotations"> The set of annotations from which to generate fluent API calls. </param>
+        IReadOnlyList<MethodCallCodeFragment> GenerateFluentApiCalls(
+            [NotNull] ISkipNavigation navigation, [NotNull] IDictionary<string, IAnnotation> annotations)
+            => Array.Empty<MethodCallCodeFragment>();
+
         /// <summary>
         ///     For the given annotations which have corresponding fluent API calls, returns those fluent API calls
         ///     and removes the annotations.

src/EFCore.Relational/Extensions/RelationalForeignKeyExtensions.cs

@@ -88,8 +88,8 @@ public static string GetDefaultName(
             {
                 IForeignKey linkedForeignKey = null;
                 foreach (var otherForeignKey in rootForeignKey.DeclaringEntityType
-                        .FindRowInternalForeignKeys(storeObject)
-                        .SelectMany(fk => fk.PrincipalEntityType.GetForeignKeys()))
+                    .FindRowInternalForeignKeys(storeObject)
+                    .SelectMany(fk => fk.PrincipalEntityType.GetForeignKeys()))
                 {
                     if (principalStoreObject.Name == otherForeignKey.PrincipalEntityType.GetTableName()
                         && principalStoreObject.Schema == otherForeignKey.PrincipalEntityType.GetSchema()
@@ -196,7 +196,7 @@ public static IForeignKey FindSharedObjectRootForeignKey([NotNull] this IForeign
             // Using a hashset is detrimental to the perf when there are no cycles
             for (var i = 0; i < Metadata.Internal.RelationalEntityTypeExtensions.MaxEntityTypesSharingTable; i++)
             {
-                IForeignKey linkedKey = null;
+                IForeignKey linkedForeignKey = null;
                 foreach (var otherForeignKey in rootForeignKey.DeclaringEntityType
                     .FindRowInternalForeignKeys(storeObject)
                     .SelectMany(fk => fk.PrincipalEntityType.GetForeignKeys()))
@@ -207,17 +207,17 @@ public static IForeignKey FindSharedObjectRootForeignKey([NotNull] this IForeign
                             otherForeignKey.PrincipalEntityType.GetSchema()))
                         == foreignKeyName)
                     {
-                        linkedKey = otherForeignKey;
+                        linkedForeignKey = otherForeignKey;
                         break;
                     }
                 }
 
-                if (linkedKey == null)
+                if (linkedForeignKey == null)
                 {
                     break;
                 }
 
-                rootForeignKey = linkedKey;
+                rootForeignKey = linkedForeignKey;
             }
 
             return rootForeignKey == foreignKey ? null : rootForeignKey;

src/EFCore.Relational/Extensions/RelationalPropertyExtensions.cs

@@ -825,7 +825,25 @@ public static bool IsColumnNullable([NotNull] this IProperty property, in StoreO
 
             return property.IsNullable
                     || (property.DeclaringEntityType.BaseType != null && property.DeclaringEntityType.GetDiscriminatorProperty() != null)
-                    || property.DeclaringEntityType.FindRowInternalForeignKeys(storeObject).Any();
+                    || IsOptionalSharingDependent(property.DeclaringEntityType, storeObject, 0);
+        }
+
+        private static bool IsOptionalSharingDependent(IEntityType entityType, in StoreObjectIdentifier storeObject, int recursionDepth)
+        {
+            if (recursionDepth++ == Metadata.Internal.RelationalEntityTypeExtensions.MaxEntityTypesSharingTable)
+            {
+                return true;
+            }
+
+            bool? optional = null;
+            foreach (var linkingForeignKey in entityType.FindRowInternalForeignKeys(storeObject))
+            {
+                optional = (optional ?? true)
+                    && (!linkingForeignKey.IsRequiredDependent
+                        || IsOptionalSharingDependent(linkingForeignKey.PrincipalEntityType, storeObject, recursionDepth));
+            }
+
+            return optional ?? false;
         }
 
         /// <summary>

src/EFCore.Relational/Storage/ParameterNameGenerator.cs

@@ -22,7 +22,7 @@ public class ParameterNameGenerator
         ///     Generates the next unique parameter name.
         /// </summary>
         /// <returns> The generated name. </returns>
-        public virtual string GenerateNext() => string.Format(CultureInfo.InvariantCulture, "p{0}", _count++);
+        public virtual string GenerateNext() => "p" + _count++;
 
         /// <summary>
         ///     Resets the generator, meaning it can reuse previously generated names.