OMEdit allows invalid connections

[massimo ceraolo]

1) OMEdit allows two output connectors to be connected to each other. For instance allows to connect the output of two Modelica.Blocks.Source.Constant blocks, which is evidently nonsense.

2) It allows also to connect to each other input connectors, such as the input connectors of two integrator blocks.

Dymola allows 2), but rejects 1).

IMO it would be better to reject both 1) and 2); but at least 1) shouldn't be allowed, as explicitly stated in section 9.3 of specification, fourth-last bullet.

OMEdit v1.12.0-dev-229-g44b8b42 (64-bit)
Connected to v1.12.0-dev-293-gec908e4 (64-bit)

DESCRIPTION EDITED ON 21/03/2020
The situation is even worse than the original description.
It looks like ANY connection is allowed by OMEdit when assembling components in a diagram: a mechanics.rotational flange to an input connector, a mechanics.translational flange into a rotational one, etc. Naturally, these are rare mistakes by a sane user. However, this can occur inadvertently, especially when we have components with different connector types, because of #4645 (and occurs to new users and students).

[Adeel Asghar]

In order to check the connectors compatibility I need to instantiate the model. We use to do this but not doing it now because of #2450.

I suggest we extend the addConnection API and check in it if the connection is valid and if not then set error message.

[Adrian Pop]

We will do some basic checks in omc when using addConnection.

[massimo ceraolo]

Maybe is not that important for OMEdit to forbid connection of outputs to each other, since it results in an over-determined system, as is clearly stated when checking and running the model.
Thus I will reduce the priority of this ticket.

[Francesco Casella]

See also the discussion in #4551

[Francesco Casella]

I think the correctness of connections should be checked by the front-end, before the equations are passed to the backend and found to have structural problems.

The question is if the new front-end is fast enough that we can make this check immediately when the connection is made, or rather only do this at compile time.

I understand that with the current front-end immediate checking is not feasible, since instantiation of Modelica.Fluid connectors just takes forever.

[Francesco Casella]

Rescheduled to 1.14.0 after 1.13.0 releasee

[Francesco Casella]

Releasing 1.14.0 which is stable and has many improvements w.r.t. 1.13.2. This issue is rescheduled to 1.16.0