Detect cyclic dependencies in property definitions

[bajtos]

While working on belongsTo relation in #1618, we discovered a need to detect circular dependencies in property definitions and provide a helpful error to users.

Here is a PoC code that did not make it to master yet:

https://github.com/strongloop/loopback-next/blob/bcd7ee98cc4958ccde595cf26e35e6f53f236401/packages/repository/src/decorators/model.decorator.ts#L90-L110

We should take a closer look at different ways how a cyclic relation can be introduced, write tests to reproduce those cases and then fix the implementation to throw an error that explains the user what went wrong and how to fix the problem.

Acceptance criteria

TBD

[bajtos]

Few examples of different ways how to create a cyclic dependency. Some of them are rejected by the compiler if all code is in the single file (but may not be detected if each model has its own source code file).

Property types read from design:type metadata:

class Wife {
 @property()
 husband: Husband;
}

class Husband {
  @property()
  wife: Wife;
}

Property types specified explicitly via a model class:

class Wife {
 @property({type: Husband})
 husband: Husband;
}

class Husband {
  @property({type: Wife})
  wife: Wife;
}

[stale]

This issue has been marked stale because it has not seen activity within six months. If you believe this to be in error, please contact one of the code owners, listed in the CODEOWNERS file at the top-level of this repository. This issue will be closed within 30 days of being stale.

[stale]

This issue has been closed due to continued inactivity. Thank you for your understanding. If you believe this to be in error, please contact one of the code owners, listed in the CODEOWNERS file at the top-level of this repository.