Fix issue when changing type of primary key

If you change the type of the primary key and call Realm::update_schema()
without a migration function, the new column will not be set as primary
key column.

CHANGELOG.md

@@ -5,7 +5,7 @@
 * None.
 
 ### Fixed
-* <How do the end-user experience this issue? what was the impact?> ([#????](https://github.com/realm/realm-core/issues/????), since v?.?.?)
+* Migrating primary key to a new type without migration function would cause an assertion to fail. ([#8045](https://github.com/realm/realm-core/issues/8045), since v10.0.0)
 * None.
 
 ### Breaking changes

src/realm/object-store/object_store.cpp

@@ -124,7 +124,8 @@ ColKey add_column(Group& group, Table& table, Property const& property)
     REALM_ASSERT(property.type != PropertyType::LinkingObjects);
 
     if (property.is_primary) {
-        // Primary key columns should have been created when the table was created
+        // Primary key columns should have been created when the table was created.
+        // Unless this is a migration
         if (auto col = table.get_column_key(property.name)) {
             return col;
         }
@@ -139,9 +140,11 @@ ColKey add_column(Group& group, Table& table, Property const& property)
     else {
         auto key =
             table.add_column(to_core_type(property.type), property.name, is_nullable(property.type), collection_type);
-        if (property.requires_index())
+        if (property.is_primary)
+            table.set_primary_key_column(key); // You can end here if this is a migration
+        else if (property.requires_index())
             table.add_search_index(key);
-        if (property.requires_fulltext_index())
+        else if (property.requires_fulltext_index())
             table.add_fulltext_index(key);
         return key;
     }

test/object-store/migrations.cpp

@@ -1137,6 +1137,31 @@ TEST_CASE("migration: Automatic", "[migration]") {
         });
     }
 
+    SECTION("change primary key from string to UUID without migration function") {
+        using namespace std::string_literals;
+        Schema schema{{"Foo",
+                       {
+                           {"_id", PropertyType::String, Property::IsPrimary{true}},
+                       }}};
+        Schema schema2{{"Foo",
+                        {
+                            {"_id", PropertyType::UUID, Property::IsPrimary{true}},
+                        }}};
+        InMemoryTestFile config;
+        config.schema_mode = SchemaMode::Automatic;
+        config.schema = schema;
+        auto realm = Realm::get_shared_realm(config);
+        realm->update_schema(schema2, 2);
+
+        CppContext ctx(realm);
+        std::any values = AnyDict{
+            {"_id", UUID("3b241101-0000-0000-0000-4136c566a964"s)},
+        };
+        realm->begin_transaction();
+        Object::create(ctx, realm, *realm->schema().find("Foo"), values);
+        realm->commit_transaction();
+    }
+
     SECTION("object accessors inside migrations") {
         using namespace std::string_literals;