Enable CSS-like linear-gradient fills for flowchart nodes

[enourbakhsh]

📑 Summary

This PR adds support for CSS-like linear-gradient fills to Mermaid, following the CSS linear-gradient syntax. It introduces a reusable gradient utility that can be applied to other diagrams in the future, though this PR focuses on flowcharts as an example of how the feature can be used.

Resolves #2907 and #4476

📏 Design Decisions

The implementation involves updating the lexer to recognize the linear-gradient syntax and modifying the renderer to correctly apply the gradient fills to flowchart nodes. The design follows a CSS-like approach to maintain familiarity for users.

📋 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.
• 🦋 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:.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4b4d347

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[netlify]

✅ Deploy Preview for mermaid-js ready!

Name	Link
🔨 Latest commit	4b4d347
🔍 Latest deploy log	https://app.netlify.com/sites/mermaid-js/deploys/66fb778026d0aa00083b97cf
😎 Deploy Preview	https://deploy-preview-5912--mermaid-js.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[pkg-pr-new]

Open in Stackblitz

pnpm add https://pkg.pr.new/mermaid-js/mermaid@5912

pnpm add https://pkg.pr.new/mermaid-js/mermaid/@mermaid-js/mermaid-zenuml@5912

pnpm add https://pkg.pr.new/mermaid-js/mermaid/@mermaid-js/layout-elk@5912

pnpm add https://pkg.pr.new/mermaid-js/mermaid/@mermaid-js/parser@5912

commit: 4b4d347

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 424 lines in your changes missing coverage. Please review.

Project coverage is 4.96%. Comparing base (17c6ed6) to head (4b4d347).
Report is 23 commits behind head on develop.

Files with missing lines	Patch %	Lines
...kages/mermaid/src/rendering-util/createGradient.ts	0.00%	336 Missing ⚠️
.../src/diagrams/flowchart/flowRenderer-v3-unified.ts	0.00%	88 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #5912      +/-   ##
==========================================
- Coverage     5.00%   4.96%   -0.05%     
==========================================
  Files          338     339       +1     
  Lines        48221   48641     +420     
  Branches       551     552       +1     
==========================================
  Hits          2413    2413              
- Misses       45808   46228     +420     

Flag	Coverage Δ
unit	4.96% <0.00%> (-0.05%)	⬇️

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

Files with missing lines	Coverage Δ
.../src/diagrams/flowchart/flowRenderer-v3-unified.ts	0.00% <0.00%> (ø)
...kages/mermaid/src/rendering-util/createGradient.ts	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes

[argos-ci]

The latest updates on your projects. Learn more about Argos notifications ↗︎

Build	Status	Details	Updated (UTC)
default (Inspect)	⚠️ Changes detected (Review)	1 removed, 1 failure	Oct 1, 2024, 4:28 AM