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

[Copilot]

Fixes #26067

Removing a migration rewrites the model snapshot, appending a redundant (string)null schema argument to every ToTable call, leaving the snapshot with spurious uncommitted changes.

-    b.ToTable("MyEntity");
+    b.ToTable("MyEntity", (string)null);

Root cause

ToTable("X") always records a null Schema annotation. When the snapshot is round-tripped — which is what migrations remove does, rebuilding the model from the snapshot — CSharpSnapshotGenerator.GenerateTableMapping re-emitted that null as , (string)null, even when the entity's default schema was already null (making the argument redundant). The migrations add path uses the live model, where a table-name-by-convention carries no schema annotation, which is why only remove reproduced it.

Changes

• CSharpSnapshotGenerator.GenerateTableMapping: emit the explicit null schema only when entityType.GetDefaultSchema() != null, so the argument is kept only when meaningful (overriding an inherited non-null schema, e.g. an owned entity under a schema-qualified owner) and dropped when redundant. Snapshot generation becomes idempotent.
• Tests:
  • ToTable_with_default_null_schema_is_not_changed_on_snapshot_round_trip (CSharpMigrationsGeneratorTest) — asserts the snapshot is stable across generate → rebuild → regenerate.
  • Convert_owned_entity_with_no_schema_to_regular_entity (MigrationsTestBase) — covers the owned-entity-under-schema case where (string)null is required; asserter is order-independent and guards schema checks behind AssertSchemaNames (SQLite has no schema support and orders tables differently). SQLite and SQL Server overrides included.

[Copilot]

Pull request overview

This PR fixes snapshot code generation so that migrations remove (which round-trips through the model snapshot) no longer introduces redundant , (string)null schema arguments on ToTable calls when the effective default schema is already null, improving snapshot idempotence.

Changes:

• Update CSharpSnapshotGenerator.GenerateTableMapping to only emit an explicit null schema argument when the entity type’s default schema is non-null (i.e., when null is an intentional override).
• Add a design-time snapshot round-trip test to ensure ToTable("X") stays stable and doesn’t become ToTable("X", (string)null) after round-tripping.
• Add/extend migrations functional coverage for converting an owned type (under a schema-qualified owner) into a regular entity while preserving the intended schema behavior across providers.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/EFCore.Design/Migrations/Design/CSharpSnapshotGenerator.cs	Avoids emitting redundant explicit-null schema arguments during snapshot generation when the default schema is already null.
test/EFCore.Design.Tests/Migrations/Design/CSharpMigrationsGeneratorTest.ModelSnapshot.cs	Adds a regression test ensuring snapshots remain identical after generate → rebuild → regenerate when default schema is null.
test/EFCore.Relational.Specification.Tests/Migrations/MigrationsTestBase.cs	Adds a provider-agnostic migration scenario covering owned-to-regular conversion with schema interplay and snapshot round-tripping.
test/EFCore.Sqlite.FunctionalTests/Migrations/MigrationsSqliteTest.cs	Adds provider-specific SQL assertions for the new owned-to-regular conversion scenario on SQLite.
test/EFCore.SqlServer.FunctionalTests/Migrations/MigrationsSqlServerTest.cs	Adds an override for the new scenario, but currently lacks SQL assertions (see comment).

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.