fix(mindmap): correct root edge attachment in tidy-tree layout

[Valley-15]

📑 Summary

Fixes an issue where root-to-child edges in mindmap diagrams using layout: tidy-tree appeared visually disconnected on the right side.

Resolves #7572
Related to #7579

---

📏 Design Decisions

• The issue was caused by intermediate routing points being added even for edges connected to the root node.
• This created bent paths that did not align properly with node boundaries, especially on the right side.
• The fix ensures that when the target node is the root, intermediate routing points are skipped.
• As a result, edges use direct paths ([startPos, endPos]) and attach correctly.

---

📋 Tasks

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests
• 📓 have added documentation
• 🦋 changeset added (not required for small bug fix)

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commit: 9f2cdd6

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Codecov Report

❌ Patch coverage is 4.08163% with 47 lines in your changes missing coverage. Please review.
✅ Project coverage is 3.33%. Comparing base (1bf8f4d) to head (9f2cdd6).
⚠️ Report is 12 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/mermaid-layout-tidy-tree/src/layout.ts	2.08%	47 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #7591   +/-   ##
=======================================
  Coverage     3.33%   3.33%           
=======================================
  Files          538     539    +1     
  Lines        56366   56333   -33     
  Branches       822     823    +1     
=======================================
+ Hits          1878    1879    +1     
+ Misses       54488   54454   -34     

Flag	Coverage Δ
unit	3.33% <4.08%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
packages/mermaid/src/config.type.d.ts	100.00% <100.00%> (ø)
packages/mermaid-layout-tidy-tree/src/layout.ts	0.24% <2.08%> (+0.01%)	⬆️

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Build	Status	Details	Updated (UTC)
default (Inspect)	⚠️ Changes detected (Review)	78 changed, 1 added	Apr 18, 2026, 11:47 AM

[knsv]

Appreciate this @Valley-15

It looks much better at the right part of the diagram but there are some new visual discepencies on the left part oif the diagram instead. Looking forward to an update! (I will also let my bot do a review)-

You can see them here:
https://app.argos-ci.com/mermaid/mermaid/builds/6471/290705813

Attaching a screenshot as well

[knsv]

[sisyphus-bot]

Thanks for tackling this, @Valley-15 — nice first contribution! The root cause analysis in your PR description is clear and the fix is well-targeted.

What's working well

🎉 [praise] Excellent diagnosis of the root cause. The intermediate routing points being added unconditionally for root-connected edges is exactly the problem, and skipping them when targetNode.section === 'root' or sourceNode.section === 'root' is the right fix. The symmetry of the 4 conditions (covering both source→root and root→target for both left and right sections) is clean.

🎉 [praise] Minimal, surgical change — 4 conditions added, zero collateral modifications. This is the ideal scope for a bug fix PR.

Things to address

🔴 [blocking] The issue with added artifacts in the left part of the diagram (See earlier comment).

🟡 [important] Missing e2e visual regression test. Since this is a rendering fix that changes how edges visually appear, it would be great to add a test case to cypress/integration/rendering/mindmap-tidy-tree.spec.js that reproduces the original bug (>5 children causing disconnected edges on the right side). This ensures the fix isn't accidentally regressed. Here's an example you could add:

it('5-tidy-tree: should render root edges correctly with many children', () => {
  imgSnapshotTest(
    ` ---
    config:
      layout: tidy-tree
    ---
    mindmap
    root((Central Idea))
      Branch1
      Branch2
      Branch3
      Branch4
      Branch5
      Branch6
      Branch7
    `
  );
});

The existing test file at cypress/integration/rendering/mindmap-tidy-tree.spec.js has 4 tests you can use as reference — they all follow the imgSnapshotTest() pattern. The key is to have enough children (>5) so that nodes appear on both left and right sides, which is the scenario from issue #7572.

🟢 [nit] Consider generating a changeset for this fix: pnpm changeset, select mermaid-layout-tidy-tree, choose patch, and prefix with fix:. Your checklist notes this as optional for small fixes, and it is — but it helps users see the fix in release notes.

Security

No XSS or injection issues identified. This change modifies purely geometric edge routing calculations with no user-input handling or DOM manipulation.

Summary

Severity	Count
🔴 blocking	1
🟡 important	1
🟢 nit	1
💡 suggestion	0
🎉 praise	2

Self-check

• At least one 🎉 praise item
• No duplicate comments
• Severity tally: 0 🔴 / 1 🟡 / 1 🟢 / 0 💡 / 2 🎉
• Verdict matches criteria: COMMENT (1 🟡, no 🔴)
• No inline comments used
• Tone check: collaborative and constructive

[knsv]

Happy you are still on this @Valley-15 !!

There are some rendering issues still: https://app.argos-ci.com/mermaid/mermaid/builds/6508/291474114

You can always check the argos output after your push, no need to wait for a maintainer. This is part of our CI and will run on each push to your PR.

A red cross does not necessarily mean it is wrong; it simply means the output has changed. For your next update, you can expect it to be red, as your PR is changing the output. Click the link and see that the visual tests align with what you want to achieve!

[Valley-15]

thanks @knsv sir for guidance I am working on this and will workout asap.

[ashishjain0512]

@Valley-15 Tag us in a comment when PR is ready for re-review or the Argos build needs verification. We'll be happy to assist.

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[Valley-15]

@ashishjain0512 sir

I tried working on the issues, especially the edge alignment and diagram rendering, but I’m still not able to fully resolve the inconsistencies (particularly the left-side discrepancies).

At this point, I feel I might not be able to take this further without guidance, so I would like to step back from this issue for now.

Thank you for your guidance.

[knsv-bot]

Hi @Valley-15 — thank you for taking the time to look into this and for the clear write-up of your approach! We really appreciate the effort.

For this particular area (mindmap / tidy-tree root edge routing) we'd like to hold off on merging a fix right now, as it overlaps with other in-flight layout work. I don't want your effort to go to waste, though — if you're up for another contribution, we'd love your help on any of the issues tagged good first issue. Those are scoped to be a good match for new contributors and are a great place to pick up something you can see through to merge.

Thanks again for giving Mermaid a try — and please do come back with a PR on one of those!