Cannot find alias for relation at ...

Issue Description

Using BaseEntity.find method and trying to filter by a property inside a related entity it throws the following error (this doesn’t happen if the property is the PK of the related entity):

Error: Cannot find alias for relation at currency
    at _loop_3 (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\query-builder\QueryBuilder.ts:954:27)
    at SelectQueryBuilder.QueryBuilder.findColumnsForPropertyPath (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\node_modules\typeorm\query-builder\QueryBuilder.js:827:27)
    at SelectQueryBuilder.<anonymous> (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\query-builder\QueryBuilder.ts:1069:68)
    at step (C:\...\node_modules\.pnpm\tslib@2.3.1\node_modules\tslib\tslib.js:143:27)
    at Object.next (C:\...\node_modules\.pnpm\tslib@2.3.1\node_modules\tslib\tslib.js:124:57)
    at SelectQueryBuilder.QueryBuilder.getWhereCondition (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\query-builder\QueryBuilder.ts:1208:80)
    at SelectQueryBuilder.where (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\query-builder\SelectQueryBuilder.ts:721:32)
    at Function.FindOptionsUtils.applyOptionsToQueryBuilder (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\find-options\FindOptionsUtils.ts:184:16)
    at Function.FindOptionsUtils.applyFindManyOptionsOrConditionsToQueryBuilder (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\find-options\FindOptionsUtils.ts:72:25)
    at EntityManager.<anonymous> (C:\...\node_modules\.pnpm\typeorm@0.2.38_ioredis@4.28.0+pg@8.7.1\src\entity-manager\EntityManager.ts:677:26)

Expected Behavior

I expect it’s possible to find rows filtering by the value of any property of a related entity and not only by its PK.

Actual Behavior

It throws Error: Cannot find alias for relation at .... See above for the complete stacktrace.

Steps to Reproduce

Example:

Entity

@Entity('countries')
export class CountryEntity extends BaseEntity {
    @PrimaryColumn({length: 2})
    id: string;

    ...

    @ManyToOne(() => CurrencyEntity, { nullable: true, eager: true })
    currency: CurrencyEntity;
}

@Entity('currencies')
export class CurrencyEntity extends BaseEntity {
    @PrimaryColumn()
    id: string;

    ...

    @Column()
    fullName: string;
}

Lets say we want to find every single country which official currency’s fullName is United States dollar

const markets = await CountryEntity.find({
    where: {
        currency:  {
            fullName: 'United States dollar'
        }
    }
});

Result: Error: Cannot find alias for relation at currency.

If you search by PK currency.id instead of fullName, it would work:

const markets = await CountryEntity.find({
    where: {
        currency:  {
            id: 'USD'
        }
    }
});

Using QueryBuilder also works.

My Environment

Additional Context

Relevant Database Driver(s)

Are you willing to resolve this issue by submitting a Pull Request?

• ✅ Yes, I have the time, but I don’t know how to start. I would need guidance.