Revert fix(flowchart): respect per-subgraph direction keyword in Dagre layout- #7672

[pbrolin47]

📑 Summary

This reverts #7672. From 11.16.0, users reports arrows between subgraphs are broken.

Resolves #7954
Resolves #7993 (alternate PR fixing part of #7954)

📏 Design Decisions

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Summary

• Reverted per-subgraph direction handling that broke arrows between nested subgraphs.
• Simplified flowchart subgraph direction data by removing explicitDir tracking.
• Restored Dagre cluster edge-copying behavior for external connections.
• Added a regression snapshot test for nested subgraphs with outgoing links.
• Added a patch changeset for Mermaid.
• Updated generated LayoutData documentation references.

[changeset-bot]

🦋 Changeset detected

Latest commit: e9bb95c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
mermaid	Patch

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[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

Flowchart subgraph direction tracking no longer uses explicit-direction flags. Dagre cluster edge extraction is simplified, related direction tests are removed, nested outgoing-link snapshot coverage is added, and a patch changeset records the revert.

Subgraph arrow behavior

Layer / File(s)	Summary
Remove explicit direction metadata packages/mermaid/src/diagrams/flowchart/..., packages/mermaid/src/diagrams/state/..., packages/mermaid/src/rendering-util/types.ts	Subgraph and node contracts no longer store explicit direction flags while inherited direction resolution remains.
Restore subgraph edge extraction packages/mermaid/src/diagrams/flowchart/flowDb.ts, packages/mermaid/src/rendering-util/layout-algorithms/dagre/mermaid-graphlib.js	Rendered subgraph directions are preserved directly, and Dagre copies qualifying cluster edges without endpoint rebinding or explicit-direction extraction.
Update regression coverage and release metadata packages/mermaid/src/rendering-util/layout-algorithms/dagre/mermaid-graphlib.spec.js, cypress/integration/rendering/flowchart/flowchart-v2.spec.js, .changeset/*, docs/config/setup/mermaid/interfaces/LayoutData.md	Direction-specific Dagre tests are removed, nested outgoing-link snapshot coverage is added, generated references are refreshed, and a patch changeset documents the revert.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• mermaid-js/mermaid#7988: Both changes modify FlowDB.getData subgraph/container rendering metadata.
• mermaid-js/mermaid#7993: Both changes modify Dagre explicit-direction cluster extraction and leaf-edge handling.

Suggested reviewers: aloisklink, knsv

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The revert restores direct subgraph direction handling and tests the nested subgraph arrow case for [#7954].
Out of Scope Changes check	✅ Passed	The remaining changes are support work for the revert, including tests and a changeset, with no clear unrelated additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly names the revert and the Dagre per-subgraph direction change that this PR undoes.
Description check	✅ Passed	The PR includes the required Summary, linked issues, and task checklist, though the Design Decisions section is left as placeholder text.

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commit: e9bb95c

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.54%. Comparing base (627fc21) to head (e9bb95c).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8005      +/-   ##
===========================================
+ Coverage    77.46%   77.54%   +0.08%     
===========================================
  Files          564      564              
  Lines        74906    74840      -66     
  Branches     12661    12644      -17     
===========================================
+ Hits         58026    58037      +11     
+ Misses       15882    15804      -78     
- Partials       998      999       +1     

Flag	Coverage Δ
e2e	70.79% <100.00%> (+0.26%)	⬆️
unit	74.80% <100.00%> (-0.03%)	⬇️

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

Files with missing lines	Coverage Δ
packages/mermaid/src/diagrams/flowchart/flowDb.ts	86.16% <100.00%> (+0.35%)	⬆️
packages/mermaid/src/diagrams/state/dataFetcher.ts	96.11% <ø> (-0.02%)	⬇️
packages/mermaid/src/diagrams/state/stateDb.ts	88.76% <ø> (ø)
...g-util/layout-algorithms/dagre/mermaid-graphlib.js	92.21% <100.00%> (-0.79%)	⬇️

... and 7 files with indirect coverage changes

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Build	Status	Details	Updated (UTC)
default (Inspect)	👍 Approved by pbrolin47	1 changed	Jul 29, 2026, 1:13 PM

[aloisklink]

Looks good to me!

Remember to re-open #4648.

I've also updated the PR description to auto-close #7993 when this PR is merged, since this PR makes that one obsolete.