Fix snapshot generation to capture column type for JSON columns

Port of #37284

Co-authored-by: AndriySvyryd <6539701+AndriySvyryd@users.noreply.github.com>

Author: Copilot

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

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Text;
+using System.Text.Json;
 using Microsoft.EntityFrameworkCore.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 
@@ -837,6 +838,20 @@ protected virtual void GenerateEntityTypeAnnotations(
             .FilterIgnoredAnnotations(entityType.GetAnnotations())
             .ToDictionary(a => a.Name, a => a);
 
+        // Add ContainerColumnType annotation if entity is mapped to JSON but the type annotation is missing
+        if (annotations.ContainsKey(RelationalAnnotationNames.ContainerColumnName)
+            && !annotations.ContainsKey(RelationalAnnotationNames.ContainerColumnType))
+        {
+            var containerColumnType = entityType.GetContainerColumnType()
+                ?? Dependencies.RelationalTypeMappingSource.FindMapping(typeof(JsonElement))?.StoreType;
+            if (containerColumnType != null)
+            {
+                annotations[RelationalAnnotationNames.ContainerColumnType] = new Annotation(
+                    RelationalAnnotationNames.ContainerColumnType,
+                    containerColumnType);
+            }
+        }
+
         GenerateTableMapping(entityTypeBuilderName, entityType, stringBuilder, annotations);
         GenerateSplitTableMapping(entityTypeBuilderName, entityType, stringBuilder);
 

test/EFCore.Design.Tests/Migrations/Design/CSharpMigrationsGeneratorTest.ModelSnapshot.cs

@@ -4362,7 +4362,9 @@ public virtual void Owned_types_mapped_to_json_are_stored_in_snapshot()
 
                             b1.ToTable("EntityWithOneProperty", "DefaultSchema");
 
-                            b1.ToJson("EntityWithTwoProperties");
+                            b1
+                                .ToJson("EntityWithTwoProperties")
+                                .HasColumnType("nvarchar(max)");
 
                             b1.WithOwner("EntityWithOneProperty")
                                 .HasForeignKey("EntityWithOnePropertyId");
@@ -4437,6 +4439,7 @@ public virtual void Owned_types_mapped_to_json_are_stored_in_snapshot()
 
                 Assert.Equal(nameof(EntityWithOneProperty), ownedType1.GetTableName());
                 Assert.Equal("EntityWithTwoProperties", ownedType1.GetContainerColumnName());
+                Assert.Equal("nvarchar(max)", ownedType1.GetContainerColumnType());
 
                 var ownership2 = ownedType1.FindNavigation(nameof(EntityWithStringKey)).ForeignKey;
                 Assert.Equal("EntityWithTwoPropertiesEntityWithOnePropertyId", ownership2.Properties[0].Name);
@@ -4473,6 +4476,83 @@ public virtual void Owned_types_mapped_to_json_are_stored_in_snapshot()
                 Assert.Equal("Name", ownedProperties3[3].Name);
             });
 
+    [ConditionalFact]
+    public virtual void Owned_types_mapped_to_json_with_explicit_column_type_are_stored_in_snapshot()
+        => Test(
+            builder =>
+            {
+                builder.Entity<EntityWithOneProperty>(b =>
+                {
+                    b.HasKey(x => x.Id).HasName("PK_Custom");
+
+                    b.OwnsOne(
+                        x => x.EntityWithTwoProperties, bb =>
+                        {
+                            bb.ToJson().HasColumnType("json");
+                            bb.Ignore(x => x.Id);
+                            bb.Property(x => x.AlternateId).HasJsonPropertyName("NotKey");
+                            bb.WithOwner(e => e.EntityWithOneProperty);
+                        });
+                });
+            },
+            AddBoilerPlate(
+                GetHeading()
+                + """
+            modelBuilder.Entity("Microsoft.EntityFrameworkCore.Migrations.Design.CSharpMigrationsGeneratorTest+EntityWithOneProperty", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("int");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
+
+                    b.HasKey("Id")
+                        .HasName("PK_Custom");
+
+                    b.ToTable("EntityWithOneProperty", "DefaultSchema");
+                });
+
+            modelBuilder.Entity("Microsoft.EntityFrameworkCore.Migrations.Design.CSharpMigrationsGeneratorTest+EntityWithOneProperty", b =>
+                {
+                    b.OwnsOne("Microsoft.EntityFrameworkCore.Migrations.Design.CSharpMigrationsGeneratorTest+EntityWithTwoProperties", "EntityWithTwoProperties", b1 =>
+                        {
+                            b1.Property<int>("EntityWithOnePropertyId")
+                                .HasColumnType("int");
+
+                            b1.Property<int>("AlternateId")
+                                .HasColumnType("int")
+                                .HasAnnotation("Relational:JsonPropertyName", "NotKey");
+
+                            b1.HasKey("EntityWithOnePropertyId");
+
+                            b1.ToTable("EntityWithOneProperty", "DefaultSchema");
+
+                            b1
+                                .ToJson("EntityWithTwoProperties")
+                                .HasColumnType("json");
+
+                            b1.WithOwner("EntityWithOneProperty")
+                                .HasForeignKey("EntityWithOnePropertyId");
+
+                            b1.Navigation("EntityWithOneProperty");
+                        });
+
+                    b.Navigation("EntityWithTwoProperties");
+                });
+""", usingSystem: false),
+            o =>
+            {
+                var entityWithOneProperty = o.FindEntityType(typeof(EntityWithOneProperty));
+                Assert.Equal("PK_Custom", entityWithOneProperty.GetKeys().Single().GetName());
+
+                var ownership1 = entityWithOneProperty.FindNavigation(nameof(EntityWithOneProperty.EntityWithTwoProperties))
+                    .ForeignKey;
+                var ownedType1 = ownership1.DeclaringEntityType;
+                Assert.Equal(nameof(EntityWithOneProperty), ownedType1.GetTableName());
+                Assert.Equal("EntityWithTwoProperties", ownedType1.GetContainerColumnName());
+                Assert.Equal("json", ownedType1.GetContainerColumnType());
+            });
+
     private class Order
     {
         public int Id { get; set; }

test/EFCore.SqlServer.Tests/Migrations/SqlServerModelDifferTest.cs

@@ -1900,4 +1900,57 @@ public void Rebuild_index_with_different_datacompression_value()
 
                 Assert.Equal(DataCompressionType.Page, annotationValue);
             });
+
+    [ConditionalFact]
+    public void Alter_column_from_nvarchar_max_to_json_for_owned_type()
+        => Execute(
+            _ => { },
+            source => source.Entity(
+                "Blog",
+                x =>
+                {
+                    x.Property<int>("Id");
+                    x.HasKey("Id");
+                    x.OwnsOne(
+                        "Details", "Details", d =>
+                        {
+                            d.Property<string>("Author");
+                            d.Property<int>("Viewers");
+                            d.ToJson();
+                        });
+                }),
+            target => target.Entity(
+                "Blog",
+                x =>
+                {
+                    x.Property<int>("Id");
+                    x.HasKey("Id");
+                    x.OwnsOne(
+                        "Details", "Details", d =>
+                        {
+                            d.Property<string>("Author");
+                            d.Property<int>("Viewers");
+                            d.ToJson().HasColumnType("json");
+                        });
+                }),
+            upOps =>
+            {
+                Assert.Equal(1, upOps.Count);
+
+                var operation = Assert.IsType<AlterColumnOperation>(upOps[0]);
+                Assert.Equal("Blog", operation.Table);
+                Assert.Equal("Details", operation.Name);
+                Assert.Equal("json", operation.ColumnType);
+                Assert.Equal("nvarchar(max)", operation.OldColumn.ColumnType);
+            },
+            downOps =>
+            {
+                Assert.Equal(1, downOps.Count);
+
+                var operation = Assert.IsType<AlterColumnOperation>(downOps[0]);
+                Assert.Equal("Blog", operation.Table);
+                Assert.Equal("Details", operation.Name);
+                Assert.Equal("nvarchar(max)", operation.ColumnType);
+                Assert.Equal("json", operation.OldColumn.ColumnType);
+            });
 }