fix: Display no arrows for open links

[jahredhope]

📑 Summary

In Flowcharts "Open links" (Links with no direction) are currently being displayed with single-directional arrows.

I believe this started occurring sometime in v11.

This change makes it so open links display with no arrow on their start or end.

Resolves #6020

📏 Design Decisions

Edges of type arrow_open should be treated as a special case, they are neither a single or double_ directional arrow.

I've added tests for single and double directional arrows to make the difference in use-case easier to see.

Example Before Change

Example After Change

📋 Tasks

I have:

• 📖 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.
• 🦋 If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. Changesets that add features should be minor and those that fix bugs should be patch. Please prefix changeset messages with feat:, fix:, or chore:.

resolves: #5813
resolves: #5964
resolves: #6020

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🦋 Changeset detected

Latest commit: ed8ba95

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

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mermaid	Patch

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commit: ed8ba95

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 4.48%. Comparing base (64554a6) to head (b357624).
Report is 4 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/mermaid/src/diagrams/flowchart/flowDb.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6093   +/-   ##
=======================================
  Coverage     4.48%   4.48%           
=======================================
  Files          383     382    -1     
  Lines        54038   54030    -8     
  Branches       596     621   +25     
=======================================
  Hits          2425    2425           
+ Misses       51613   51605    -8     

Flag	Coverage Δ
unit	4.48% <0.00%> (+<0.01%)	⬆️

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	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes

[jahredhope]

I'm not sure why the code coverage is failing. I expect it's incorrectly reporting as not covered, as it says the whole file as no coverage.

I'll try and dig into it, but I may need some help if anyone knows why it's reporting as such.

[jahredhope]

I didn't realise someone had raised a fix for this ~3 weeks ago. My solution is a little different in that it results in an end type of 'none' rather than "arrow_open" which I like the explicitness of. So I'm leaving my PR open for the maintainers to pick which they prefer.

[jahredhope]

I think there are actually a few issues and multiple fixes for the same thing. Perhaps they should be closed as duplicates for the original one?

• Flowchart arrowless edges stopped working in v11 #5813 (Sept 3rd)
• Open links rendering as arrow links in the live editor on flowcharts and graphs perhaps other chart types also #5964 (Oct 16th)
• OPen link does not work #6020 (Nov 4th)
• Open link has arrow head in flowchart mermaid-live-editor#1550 (Sept 3rd, Mermaid Live)

Changes

• Fix rendering flowchart open links with arrows #6043 (3 weeks ago)
• fix: Display no arrows for open links #6093 (This one)