Feature/7078 Allow decimal sequence numbers

[milesspencer35]

📑 Summary

Added support for sequence numbers in sequence diagrams to use decimal values up to the hundredths place, and enabled incrementing using decimal values to the same precision.

Resolves #7078

📏 Design Decisions

Describe the way your implementation works or what design decisions you made if applicable.

• Updated the Jison parser for sequence diagrams to accept decimal values to the hundredths place.
• Updated how the sequenceIndex and sequenceIndexStep are added to remove floating-point errors.
• Decrease the font size once a sequence number gets sufficiently long and spills out of the circle. I decided this was the best course of action because it was a simple fix for a rare use case.

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🦋 Changeset detected

Latest commit: 1290065

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

This PR includes changesets to release 1 package

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mermaid	Minor

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Codecov Report

❌ Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 3.55%. Comparing base (717d3b3) to head (1290065).
⚠️ Report is 136 commits behind head on develop.

Files with missing lines	Patch %	Lines
.../mermaid/src/diagrams/sequence/sequenceRenderer.ts	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #7132      +/-   ##
==========================================
- Coverage     3.55%   3.55%   -0.01%     
==========================================
  Files          474     473       -1     
  Lines        47453   47504      +51     
  Branches       730     731       +1     
==========================================
  Hits          1687    1687              
- Misses       45766   45817      +51     

Flag	Coverage Δ
unit	3.55% <0.00%> (-0.01%)	⬇️

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Files with missing lines	Coverage Δ
.../mermaid/src/diagrams/sequence/sequenceRenderer.ts	0.06% <0.00%> (-0.01%)	⬇️

... and 13 files with indirect coverage changes

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Build	Status	Details	Updated (UTC)
default (Inspect)	⚠️ Changes detected (Review)	1 added	Nov 18, 2025, 5:05 PM

[shubhamparikh2704]

Please add changeset and some rendering tests

[Copilot]

Pull Request Overview

This PR adds support for decimal sequence numbers in sequence diagrams, allowing values up to the hundredths place (e.g., 10.25). The implementation includes parser updates to accept decimal values, renderer modifications to handle floating-point arithmetic correctly, and dynamic font sizing for longer sequence numbers.

Key Changes:

• Updated Jison parser to accept decimal numbers up to two decimal places
• Implemented proper rounding to avoid floating-point precision errors
• Added dynamic font sizing based on sequence number length

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison	Updated NUM token regex to accept decimal values up to hundredths place
packages/mermaid/src/diagrams/sequence/sequenceRenderer.ts	Added floating-point rounding fix and dynamic font sizing for sequence numbers
packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js	Added unit tests for decimal number support and precision validation
cypress/integration/rendering/sequencediagram.spec.js	Added integration test for decimal sequence number rendering
packages/mermaid/src/docs/syntax/sequenceDiagram.md	Documented new decimal sequence number feature with examples
docs/syntax/sequenceDiagram.md	Documented new decimal sequence number feature with examples
.changeset/slick-maps-hear.md	Added changeset entry for the feature

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[milesspencer35]

I'm not sure why this is duplicating. I've tried a couple of things to fix it, like manually removing it and reverting to an older version when a manual change hadn't been made, but neither worked. Any ideas?

[milesspencer35]

@shubhamparikh2704 @sidharthv96 I wasn't able to figure out why this was duplicating so I made a new branch, updated my docs change, and created a new PR. Here is the PR: #7174