Fix redundant (string)null schema argument in ToTable snapshot generation (#38424)

Fixes #26067

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

Author: Copilot

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

@@ -1204,7 +1204,9 @@ private void GenerateTableMapping(
             }
 
             if (schema != null
-                || (schemaAnnotation != null && tableName != null))
+                || (schemaAnnotation != null
+                    && tableName != null
+                    && entityType.GetDefaultSchema() != null))
             {
                 stringBuilder
                     .Append(", ");

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

@@ -1105,6 +1105,31 @@ public void Views_are_stored_in_the_model_snapshot()
 """),
             o => Assert.Equal("EntityWithOneProperty", o.GetEntityTypes().Single().GetViewName()));
 
+    [Fact] // Issue #26067
+    public void ToTable_with_default_null_schema_is_not_changed_on_snapshot_round_trip()
+    {
+        // When the default schema is null, regenerating the snapshot from a model that was itself
+        // built from a snapshot (as happens when removing a migration) must not add a redundant
+        // ", (string)null" schema argument to every ToTable call.
+        var modelBuilder = CreateConventionalModelBuilder();
+        modelBuilder.HasDefaultSchema(null);
+        modelBuilder.Model.RemoveAnnotation(CoreAnnotationNames.ProductVersion);
+        modelBuilder.Entity<EntityWithOneProperty>().Ignore(e => e.EntityWithTwoProperties);
+
+        var model = modelBuilder.FinalizeModel(designTime: true, skipValidation: true);
+
+        var generator = CreateMigrationsGenerator();
+        var code = generator.GenerateSnapshot("RootNamespace", typeof(DbContext), "Snapshot", model);
+
+        Assert.Contains(@"b.ToTable(""EntityWithOneProperty"");", code);
+        Assert.DoesNotContain("(string)null", code);
+
+        var roundTrippedModel = BuildModelFromSnapshotSource(code);
+        var roundTrippedCode = generator.GenerateSnapshot("RootNamespace", typeof(DbContext), "Snapshot", roundTrippedModel);
+
+        Assert.Equal(code, roundTrippedCode, ignoreLineEndingDifferences: true);
+    }
+
     [Fact]
     public void Views_with_schemas_are_stored_in_the_model_snapshot()
         => Test(

test/EFCore.Relational.Specification.Tests/Migrations/MigrationsTestBase.cs

@@ -1429,6 +1429,60 @@ public virtual Task Alter_column_reset_collation()
                 Assert.Null(nameColumn.Collation);
             });
 
+    [Fact]
+    public virtual async Task Convert_owned_entity_with_no_schema_to_regular_entity()
+        => await Test(
+            common =>
+            {
+                common.HasDefaultSchema(null);
+                common.Entity(
+                    "Entity", e =>
+                    {
+                        e.Property<int>("Id").ValueGeneratedOnAdd();
+                        e.HasKey("Id");
+                        e.Property<string>("Name");
+                        e.ToTable("Entity", "MySchema");
+                    });
+            },
+            source =>
+            {
+                source.Entity(
+                    "Entity", e =>
+                    {
+                        e.OwnsOne(
+                            "Owned", "OwnedReference", o =>
+                            {
+                                o.Property<DateTime>("Date");
+                                o.ToTable("Owned", (string)null);
+                            });
+                    });
+            },
+            target =>
+            {
+                target.Entity(
+                    "Owned", e =>
+                    {
+                        e.Property<int>("EntityId").ValueGeneratedNever();
+                        e.HasKey("EntityId");
+                        e.Property<DateTime>("Date");
+                        e.ToTable("Owned", (string)null);
+                    });
+            },
+            model =>
+            {
+                Assert.Equal(2, model.Tables.Count());
+
+                var ownedTable = model.Tables.Single(t => t.Name == "Owned");
+                var entityTable = model.Tables.Single(t => t.Name == "Entity");
+
+                if (AssertSchemaNames)
+                {
+                    Assert.Equal("MySchema", entityTable.Schema);
+                    Assert.NotEqual("MySchema", ownedTable.Schema);
+                }
+            });
+
+#pragma warning disable EF8001 // Owned JSON entities are obsolete
     [Fact]
     public virtual async Task Convert_json_entities_to_regular_owned()
         => await Test(

test/EFCore.SqlServer.FunctionalTests/Migrations/MigrationsSqlServerTest.cs

@@ -1450,6 +1450,16 @@ FROM [sys].[columns] [c]
 """);
     }
 
+    public override async Task Convert_owned_entity_with_no_schema_to_regular_entity()
+    {
+        await base.Convert_owned_entity_with_no_schema_to_regular_entity();
+
+        AssertSql(
+            """
+ALTER TABLE [Owned] DROP CONSTRAINT [FK_Owned_Entity_EntityId];
+""");
+    }
+
     public override async Task Convert_json_entities_to_regular_owned()
     {
         await base.Convert_json_entities_to_regular_owned();

test/EFCore.Sqlite.FunctionalTests/Migrations/MigrationsSqliteTest.cs

@@ -1098,6 +1098,41 @@ public override async Task Alter_column_reset_collation()
 """);
     }
 
+    public override async Task Convert_owned_entity_with_no_schema_to_regular_entity()
+    {
+        await base.Convert_owned_entity_with_no_schema_to_regular_entity();
+
+        AssertSql(
+            """
+CREATE TABLE "ef_temp_Owned" (
+    "EntityId" INTEGER NOT NULL CONSTRAINT "PK_Owned" PRIMARY KEY,
+    "Date" TEXT NOT NULL
+);
+""",
+            //
+            """
+INSERT INTO "ef_temp_Owned" ("EntityId", "Date")
+SELECT "EntityId", "Date"
+FROM "Owned";
+""",
+            //
+            """
+PRAGMA foreign_keys = 0;
+""",
+            //
+            """
+DROP TABLE "Owned";
+""",
+            //
+            """
+ALTER TABLE "ef_temp_Owned" RENAME TO "Owned";
+""",
+            //
+            """
+PRAGMA foreign_keys = 1;
+""");
+    }
+
     public override async Task Convert_json_entities_to_regular_owned()
     {
         await base.Convert_json_entities_to_regular_owned();