fix(schema): allow using non-abstract root entity in STI

Closes #874

packages/knex/src/schema/SchemaGenerator.ts

@@ -570,7 +570,10 @@ export class SchemaGenerator {
   }
 
   private getOrderedMetadata(): EntityMetadata[] {
-    const metadata = Object.values(this.metadata.getAll()).filter(meta => !meta.discriminatorValue && !meta.embeddable);
+    const metadata = Object.values(this.metadata.getAll()).filter(meta => {
+      const isRootEntity = meta.root === meta;
+      return isRootEntity && !meta.embeddable;
+    });
     const calc = new CommitOrderCalculator();
     metadata.forEach(meta => calc.addNode(meta.name!));
     let meta = metadata.pop();

tests/__snapshots__/single-table-inheritance.mysql.test.ts.snap

@@ -0,0 +1,8 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`single table inheritance in mysql non-abstract root entity 1`] = `
+"create table \`person\` (\`id\` varchar not null, \`type\` text check (\`type\` in ('person', 'employee')) not null, \`number\` integer null, primary key (\`id\`));
+create index \`person_type_index\` on \`person\` (\`type\`);
+
+"
+`;

tests/single-table-inheritance.mysql.test.ts

@@ -1,4 +1,4 @@
-import { Dictionary, MetadataDiscovery, MetadataStorage, MikroORM, ReferenceType, wrap } from '@mikro-orm/core';
+import { Dictionary, Entity, MetadataDiscovery, MetadataStorage, MikroORM, PrimaryKey, Property, ReferenceType, wrap } from '@mikro-orm/core';
 import { MySqlDriver } from '@mikro-orm/mysql';
 import { BaseUser2, CompanyOwner2, Employee2, Manager2, Type } from './entities-sql';
 import { initORMMySql, wipeDatabaseMySql } from './bootstrap';
@@ -165,6 +165,38 @@ describe('single table inheritance in mysql', () => {
     expect(discovered.get('C').discriminatorValue).toBe('c');
   });
 
+  test('non-abstract root entity', async () => {
+    @Entity({
+      discriminatorColumn: 'type',
+      discriminatorMap: {
+        person: 'Person',
+        employee: 'Employee',
+      },
+    })
+    class Person {
+
+      @PrimaryKey()
+      id!: string;
+
+    }
+
+    @Entity()
+    class Employee extends Person {
+
+      @Property()
+      number?: number;
+
+    }
+
+    const orm = await MikroORM.init({
+      entities: [Person, Employee],
+      type: 'sqlite',
+      dbName: ':memory:',
+    });
+    const sql = await orm.getSchemaGenerator().getCreateSchemaSQL(false);
+    expect(sql).toMatchSnapshot();
+  });
+
   afterAll(async () => orm.close(true));
 
 });