fix: empty objects being hydrated when eager loading relations that h…

…ave a `@VirtualColumn` (#10432)

* test: add scenario for #10431

* fix: empty objects being hydrated by unselected virtual properties

src/query-builder/SelectQueryBuilder.ts

@@ -2882,6 +2882,11 @@ export class SelectQueryBuilder<Entity extends ObjectLiteral>
                     })
                 })
             } else {
+                if (column.isVirtualProperty) {
+                    // Do not add unselected virtual properties to final select
+                    return
+                }
+
                 finalSelects.push({
                     selection: selectionPath,
                     aliasName: DriverUtils.buildAlias(

test/github-issues/10431/entity/Category.ts

@@ -0,0 +1,26 @@
+import {
+    Column,
+    Entity,
+    ManyToMany,
+    PrimaryGeneratedColumn,
+    VirtualColumn,
+} from "../../../../src"
+import { Product } from "./Product"
+
+@Entity()
+export class Category {
+    @PrimaryGeneratedColumn()
+    id: number
+
+    @VirtualColumn({
+        query: (alias) =>
+            `SELECT COUNT(*) FROM category WHERE id = ${alias}.id`,
+    })
+    randomVirtualColumn: number
+
+    @ManyToMany(() => Product, (product: Product) => product.categories)
+    products?: Product[]
+
+    @Column("varchar")
+    name: string
+}

test/github-issues/10431/entity/Product.ts

@@ -0,0 +1,25 @@
+import {
+    Column,
+    Entity,
+    JoinTable,
+    ManyToMany,
+    PrimaryGeneratedColumn,
+} from "../../../../src"
+import { Category } from "./Category"
+
+@Entity()
+export class Product {
+    @PrimaryGeneratedColumn()
+    id: number
+
+    @Column("varchar")
+    name: string
+
+    @ManyToMany(() => Category, (category: Category) => category.products, {
+        eager: true,
+        cascade: ["insert", "update", "remove"],
+        orphanedRowAction: "delete",
+    })
+    @JoinTable()
+    categories: Category[]
+}

test/github-issues/10431/entity/index.ts

@@ -0,0 +1,2 @@
+export * from "./Category"
+export * from "./Product"

test/github-issues/10431/issue-10431.ts

@@ -0,0 +1,42 @@
+import "reflect-metadata"
+import {
+    createTestingConnections,
+    closeTestingConnections,
+    reloadTestingDatabases,
+} from "../../utils/test-utils"
+import { DataSource } from "../../../src"
+import { expect } from "chai"
+
+import { Category, Product } from "./entity"
+
+describe("github issues > #10431 When requesting nested relations on foreign key primary entities, relation becomes empty entity rather than null", () => {
+    let connections: DataSource[]
+    before(
+        async () =>
+            (connections = await createTestingConnections({
+                entities: [Category, Product],
+                schemaCreate: true,
+                dropSchema: true,
+            })),
+    )
+    beforeEach(() => reloadTestingDatabases(connections))
+    after(() => closeTestingConnections(connections))
+
+    it("should return [] when requested nested relations are empty on ManyToMany relation with @VirtualColumn definitions", () =>
+        Promise.all(
+            connections.map(async (connection) => {
+                const productRepo = connection.getRepository(Product)
+                const testProduct = new Product()
+                testProduct.name = "foo"
+                await productRepo.save(testProduct)
+                const foundProduct = await productRepo.findOne({
+                    where: {
+                        id: testProduct.id,
+                    },
+                    relations: { categories: true },
+                })
+                expect(foundProduct?.name).eq("foo")
+                expect(foundProduct?.categories).eql([])
+            }),
+        ))
+})