fix(core): fix querying by embedded properties inside relations

Closes #5391

packages/knex/src/query/QueryBuilderHelper.ts

@@ -780,7 +780,13 @@ export class QueryBuilderHelper {
     } else {
       const [a, ...rest] = field.split('.');
       const f = rest.join('.');
-      ret = a + '.' + this.fieldName(f, a, always, idx);
+      const fieldName = this.fieldName(f, a, always, idx) as string | RawQueryFragment;
+
+      if (fieldName instanceof RawQueryFragment) {
+        return fieldName.sql;
+      }
+
+      ret = a + '.' + fieldName;
     }
 
     if (quote) {

tests/features/embeddables/GH5391.test.ts

@@ -0,0 +1,100 @@
+import { Embeddable, Embedded, Entity, ManyToOne, MikroORM, PrimaryKey, Property, Ref } from '@mikro-orm/libsql';
+
+@Embeddable()
+class RoleMeta {
+
+  @Property()
+  testString!: string;
+
+}
+
+@Entity()
+class Role {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property()
+  name!: string;
+
+  @Embedded({ entity: () => RoleMeta, nullable: true, object: true })
+  meta?: RoleMeta;
+
+}
+
+@Entity()
+class User {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property()
+  name!: string;
+
+  @Property({ unique: true })
+  email!: string;
+
+  @ManyToOne(() => Role, { ref: true })
+  role!: Ref<Role>;
+
+}
+
+let orm: MikroORM;
+
+beforeAll(async () => {
+  orm = MikroORM.initSync({
+    dbName: ':memory:',
+    entities: [User, Role, RoleMeta],
+  });
+  await orm.schema.createSchema();
+});
+
+afterAll(async () => {
+  await orm.close(true);
+});
+
+test('Fetching an entity by a field in embeddable of a relation - does not work', async () => {
+  orm.em.create(Role, { name: 'Foo', meta: { testString: 'test' } });
+  await orm.em.flush();
+  orm.em.clear();
+
+  const role = await orm.em.findOneOrFail(Role, { name: 'Foo' });
+  orm.em.create(User, { name: 'Foo', email: 'foo', role });
+  await orm.em.flush();
+  orm.em.clear();
+
+  const user = await orm.em.findOneOrFail(User, {
+    email: 'foo',
+    role: {
+      meta: {
+        testString: 'test',
+      },
+    },
+  });
+  expect(user.name).toBe('Foo');
+  user.name = 'Bar';
+  orm.em.remove(user);
+  await orm.em.flush();
+
+  const count = await orm.em.count(User, { email: 'foo' });
+  expect(count).toBe(0);
+});
+
+test('Fetching an entity by a field in embeddable - working', async () => {
+  orm.em.create(Role, { name: 'Foo1', meta: { testString: 'test1' } });
+  await orm.em.flush();
+  orm.em.clear();
+
+  const role = await orm.em.findOneOrFail(Role, {
+    meta: {
+      testString: 'test1',
+    },
+  });
+
+  expect(role.name).toBe('Foo1');
+  orm.em.remove(role);
+  await orm.em.flush();
+
+  const count = await orm.em.count(Role, { name: 'Foo1' });
+  expect(count).toBe(0);
+});