Per Östlund

> I think `getElements` doesn't return `internalThermalPort` so OMEdit doesn't have the component and as a result unable to draw the connections. `getElements` just returns the elements in the class...

If I manually flatten the model with `--unitChecking` it does run the unit checker, but it doesn't produce any errors. So either something is wrong with the unit checking or...

> Unfortunately, I will not have time in December and I am not even sure who ported the implementation to the frontend. @perost do you know? I ported it to...

> * the `--unitChecking` flag is set, and then `instantiateModel()` is ran. I looked it up in the [Compiler Flags](https://openmodelica.org/doc/OpenModelicaUsersGuide/latest/omchelptext.html) page, but couldn't find that flag. Is it only missing...

> EDIT: Forget about it, now I understand that string is hardcoded into the omc source code, it is not coming from some environment variable. That's ok. Correct, there's a...

#5685 was fixed in #9446, and the issue that `A = L^3` wasn't caught should be fixed in #9447 (mea culpa, I made a typo when translating the unit checker...

> What about leaving this entirely to the backend? I mean, differentiating stuff seem more like backend than frontend stuff. The NF could just pass the partial derivative function declarations...

#10649 adds support for partial derivatives of functions in the frontend, mostly just passing them through with some error checking. Some things to consider: * It's only enabled when using...

Remove this line to allow using the old backend: https://github.com/OpenModelica/OpenModelica/blob/49a37d93a80e898db2604c62f8add2e37e5e24d9/OMCompiler/Compiler/NFFrontEnd/NFInst.mo#L640 I tried it out but as expected the old backend just fails with no error right now.

Thanks! I'll have to take a closer look tomorrow, but some immediate things: - `ModelicaCompliance.Connections.Expandable.AugmentArray` started working, it needs to be removed from the [expected failures file](https://github.com/OpenModelica/OpenModelica/blob/master/.CI/compliance.failures) for the PR...