fix(core): handle $fulltext search correctly in nested queries

Closes #3696

packages/knex/src/query/QueryBuilderHelper.ts

@@ -486,10 +486,15 @@ export class QueryBuilderHelper {
     }
 
     if (op === '$fulltext') {
-      const meta = this.metadata.get(this.entityName);
-      const columnName = key.includes('.') ?  key.split('.')[1] : key;
+      const [a, f] = this.splitField(key);
+      const prop = this.getProperty(f, a);
 
-      qb[m](this.knex.raw(this.platform.getFullTextWhereClause(meta.properties[columnName]), {
+      /* istanbul ignore next */
+      if (!prop) {
+        throw new Error(`Cannot use $fulltext operator on ${key}, property not found`);
+      }
+
+      qb[m](this.knex.raw(this.platform.getFullTextWhereClause(prop), {
         column: this.mapper(key, type, undefined, null),
         query: value[op],
       }));

tests/issues/GH3696.test.ts

@@ -0,0 +1,90 @@
+import { Collection, Entity, Index, ManyToMany, PrimaryKey, Property, Unique } from '@mikro-orm/core';
+import { FullTextType, MikroORM } from '@mikro-orm/postgresql';
+
+@Entity()
+@Unique({ properties: ['name'] })
+export class Artist {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property()
+  name: string;
+
+  @Index({ type: 'fulltext' })
+  @Property({ type: FullTextType, onUpdate: (artist: Artist) => artist.name })
+  searchableName!: string;
+
+  constructor(artist: any) {
+    this.id = artist.id;
+    this.name = artist.name;
+    this.searchableName = artist.name;
+  }
+
+}
+
+@Entity()
+export class Song {
+
+  @PrimaryKey()
+  id!: number;
+
+  @Property()
+  title: string;
+
+  @ManyToMany(() => Artist)
+  artists = new Collection<Artist>(this);
+
+  @Index({ type: 'fulltext' })
+  @Property({ type: FullTextType, onUpdate: (song: Song) => song.title })
+  searchableTitle!: string;
+
+  constructor(song: any) {
+    this.id = song.id;
+    this.title = song.title;
+    this.searchableTitle = song.title;
+  }
+
+}
+
+let orm: MikroORM;
+
+beforeAll(async () => {
+  orm = await MikroORM.init({
+    entities: [Song],
+    dbName: 'mikro_orm_test_3696',
+  });
+  await orm.schema.refreshDatabase();
+});
+
+afterAll(async () => {
+  await orm.close(true);
+});
+
+test('GH issue 3696', async () => {
+  const artist = orm.em.create(Artist, {
+    name: 'Taylor Swift',
+    searchableName: 'Taylor Swift',
+  });
+  const song = orm.em.create(Song, {
+    title: 'Anti-Hero',
+    searchableTitle: 'Anti--Hero',
+  });
+  song.artists.add(artist);
+  await orm.em.flush();
+  orm.em.clear();
+
+  const results = await orm.em.find(Song, {
+    searchableTitle: { $fulltext: 'anti' },
+    artists: { searchableName: { $fulltext: 'taylor' } },
+  }, { populate: ['artists'] });
+  expect(results).toHaveLength(1);
+  expect(results[0]).toMatchObject({
+    title: 'Anti-Hero',
+    searchableTitle: "'anti':1 'hero':2",
+  });
+  expect(results[0].artists[0]).toMatchObject({
+    name: 'Taylor Swift',
+    searchableName: "'swift':2 'taylor':1",
+  });
+});