Bug/5059 fix external connection after updating edges

[mathbraga]

📑 Summary

Signals a subgraph with the external connection flag in case one of its children is used as an anchor node linking to outside.

Resolves #5059

📏 Design Decisions

So when a subgraph has a link to an outside node, it picks a "fake node" to be used as a reference for edges it is part of. The issue is that when it does so to a node that is part of another internal subgraph, this subgraph will now also have a link to the outside, so it needs to be updated with the cluster.externalConnections = true.

Only solving the issue described above can make some layouts look inconsistent, the one reported in #5059 would look like this:

I believe this behaviour occurs because dagre-d3 identifies the edge going down from WireProperty1 (the fake node in this case), and positions the nodes horizontally so that the edge won't cut through other child nodes in the subgraph.

So I also added an implementation to change the fake node to its parent in case it does not originally have outside links, making it a valid target for an edge. In my opinion the resulting layout better represents its input code:

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
• 🔖 targeted develop branch

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7b62466) 79.32% compared to head (679f77d) 79.34%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5127      +/-   ##
===========================================
+ Coverage    79.32%   79.34%   +0.01%     
===========================================
  Files          167      167              
  Lines        13873    13882       +9     
  Branches       707      707              
===========================================
+ Hits         11005    11014       +9     
  Misses        2715     2715              
  Partials       153      153              

Flag	Coverage Δ
e2e	85.13% <100.00%> (+0.01%)	⬆️
unit	43.04% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...ages/mermaid/src/dagre-wrapper/mermaid-graphlib.js	91.32% <100.00%> (+0.37%)	⬆️