fix: allow HierarchicalLayout to manage circular dependencies

[Franz-Ritter]

Summary
Solved bug creating a graph with a circular dependency using the HiearchlLayout.ts algorithm.

Check this issue for more detailed information including an example to reproduce the bug

Solution:

Uncomment the isAncestor method GraphHierachyNode, which is used by HiearchlLayout. The uncommented implementation makes sure, that a circular dependency is detected and resolved. Using the default isAncestor does not work at this point, because the parent nodes of the child nodes in the graph are not set.

Closes #231

[tbouffard]

Hi @Franz-Ritter did you try to add automatic tests as I suggested in the issue?

This would reproduce the initial problem and show that is now fixed.

[Franz-Ritter]

Hi @tbouffard, Sorry I oversaw your comment. I try to find time to check how you structure your tests, and add one to the PR as requested.

[Franz-Ritter]

@tbouffard I added a test which creates a cyclic Graph and a non-cyclic graph.
Please consider that I am not a native typescript developer...
Anyway, both graph used to work using mxGraph. When you do and checkout the code and execute the test without the change in GraphHierarchyNode one of the tests fails. However, my change let both test pass.

If you have any questions or need more input, please let me know. Applying that fix on the code base would help me a lot. Atm i am forced to package and link the change locally.

[Franz-Ritter]

@tbouffard Do you need some additional input?

[tbouffard]

Hi @Franz-Ritter
I have been busy at work and I haven't had time to have a look at this Pull Request.
I will check it in a few days.

[tbouffard]

@Franz-Ritter It's all good to me. Thanks

• ✔️ reproduce the issue with newly introduced tests (prior the fix is applied)
• ℹ️ I push directly some lint fixes in the branch of this PR