feat: allow specifying on which weekday a tickInterval should start

[leinelissen]

📑 Summary

By default, d3 intervals start on Sunday as opposed to Monday. This is really unhelpful as Gantt charts are often used to play workweeks running from Monday to Friday. This means that all tasks that are aligned to workweeks are misaligned by a day when using tickInterval 1week.

📏 Design Decisions

This pull request replaces d3's timeWeek with timeMonday, so that all week-based tickIntervals start on a Monday. Alternatively, I could implement multiple options for starting weekdays (using e.g. 1week-monday or 1week-wednesday), but I feel like weeks starting on Monday are a sensible default.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 📓 have added documentation (if appropriate)
• 🔖 targeted develop branch

[codecov]

Codecov Report

Merging #4634 (39ccad8) into develop (840609a) will increase coverage by 31.71%.
The diff coverage is 82.35%.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #4634       +/-   ##
============================================
+ Coverage    45.28%   77.00%   +31.71%     
============================================
  Files           52      143       +91     
  Lines         6633    14470     +7837     
  Branches        18      516      +498     
============================================
+ Hits          3004    11143     +8139     
+ Misses        3629     3222      -407     
- Partials         0      105      +105     

Flag	Coverage Δ
e2e	83.96% <90.90%> (?)
unit	45.32% <66.66%> (+0.03%)	⬆️

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

Impacted Files	Coverage Δ
...ckages/mermaid/src/diagrams/gantt/ganttRenderer.js	87.37% <80.00%> (ø)
packages/mermaid/src/diagrams/gantt/ganttDb.js	78.23% <83.33%> (+1.48%)	⬆️

... and 135 files with indirect coverage changes

[Yokozuna59]

Hi there @leinelissen , thank for you contribution!

I like the idea of making diagrams on another day instead of Sunday, but the approach you are taking isn't right. Many users already created their diagrams relying on Sunday as a starting day; making such a change would affect the output of those diagrams, which isn't right.

A better approach would be updating the grammar of the diagram to let users specify the starting day of the week, something like this:

gantt
weekday mon

Note that this is just a suggestion, we might need to modify it or something.

[Yokozuna59]

I'm not sure if you are still interested in continuing working on it; if you are, you could rename the PR name and continue working. If not, please create an issue and close this PR.

[leinelissen]

Hey @Yokozuna59, thanks for the feedback. I get that this is a breaking change, although I do feel like ISO points to Monday being the right starting day. Nonetheless, making an option out of this does sound like a good solution. I will take a stab at implementing this, although this will make the implementation more involved. I might need your help with some drafts before I manage to pull it off.

[Yokozuna59]

Nonetheless, making an option out of this does sound like a good solution. I will take a stab at implementing this, although this will make the implementation more involved.

Great!

I might need your help with some drafts before I manage to pull it off.

Sure! I'm thinking of weekday or startWeekday with 3-letter day, what do you think?

[leinelissen]

I've gone with weekday and the full name of the day for now, as this matches tickInterval most closely (e.g. 1week, 3days).

[leinelissen]

Okay I think I've managed an implementation. If you have any feedback on it, please let me know!

[Yokozuna59]

Just minor changes.

[Yokozuna59]

Sorry for the late review I was busy, more minor changes :)

[Yokozuna59]

Final changes needed :)

[Yokozuna59]

LGTM, thanks for contribution!

I'll leave the PR open for some time so that if someone from the team wants to highlight something.

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[Yokozuna59]

@leinelissen sorry there is something we have forgotten, weekends.

If we changed the start of the week, that would mean we had new weekends, am I right?

The result of excludes weekends option need to be modified.

I'll create an issue for it, feel free to work on it if you want.