feat(tasks): add Gantt timeline view for tasks

[paryanineil]

Summary

Adds a Timeline (Gantt) view to the Tasks page, alongside List and Kanban. Each task is drawn as a horizontal bar spanning its start_date → due_date on a scrollable day axis, grouped by project.

What's included

• TaskTimeline component
  • Tasks grouped by project, one row each, with sticky task labels on the left
  • Status-colored bars positioned by start/due date (a task with only one date renders a single-day bar)
  • Today column highlighted on the axis
  • An "Unscheduled" tray lists tasks with no start/due date, so none are hidden
  • Clicking a bar opens the existing Task Details sheet
• Timeline toggle added to the Tasks view switcher
• Saveable view — adds timeline to Hive View.view_type; the mode is restored from saved views and the sidebar

Notes

• Additive — no changes to List/Kanban behavior and no backend API changes. The one backend change is a new option on the existing Hive View.view_type Select field.
• Existing task filters (status / priority / project / assignee) apply to the timeline.
• Built with date-fns (already a dependency); no new packages.
• Heads-up: touches the same view-switcher area as feat(tasks): add calendar view for tasks (month / week / day) #178 (calendar) — if that lands first I'm happy to rebase.

Testing

• tsc --noEmit and ESLint clean on the changed files.
• Verified in-browser on a seeded dataset (~77 tasks / 8 projects): bars render on the correct dates, group by project, scroll horizontally, today is highlighted, and clicking a bar opens the task sheet. No console errors.

[Rl0007]

please add demo video and resolve the conflicts

[greptile-apps]

Greptile Summary

Adds a Gantt-style Timeline view to the Tasks page, rendering each task as a horizontal bar spanning its start_date→due_date on a scrollable day axis grouped by project. The implementation is entirely additive — existing List, Kanban, and Calendar views are untouched.

• TaskTimeline component: handles single-date tasks, reversed date ranges, tasks with no dates (shown in an "Unscheduled" tray), today-column highlighting, and status-coloured bars via TASK_STATUS_COLOR. The UTC date-parsing concern raised in review has been resolved with the parseLocalDate helper.
• TasksPage integration: passes the pre-existing projectMap directly as projectTitles, avoiding a duplicate memo; the saved-view label, viewFiltersModified detection, and the save-dialog display all include the new "timeline" mode.
• Schema/type changes: "timeline" is appended to the Frappe view_type Select field and to the HiveView.view_type TypeScript union.

Confidence Score: 5/5

Safe to merge — the change is purely additive with no modifications to existing views or backend APIs.

All four changed files introduce the new timeline mode without touching existing paths. The UTC date-parsing fix (T00:00:00 local-time literal) is correctly applied, the projectMap is reused without duplication, and edge cases (single-date tasks, reversed ranges, tasks without dates) are all handled. No issues were found beyond the DOM-node scalability note already raised in the prior review thread.

No files require special attention.

Important Files Changed

Filename	Overview
frontend/src/components/TaskTimeline.tsx	New Gantt component; UTC date-parsing bug addressed via parseLocalDate; logic for single-date tasks, reversed ranges, and unscheduled tasks all handled correctly
frontend/src/pages/TasksPage.tsx	Adds timeline toggle and renders TaskTimeline with the pre-existing projectMap; no duplicate memo; view type label and saved-view logic updated correctly
frontend/src/types.ts	Adds "timeline" to the HiveView.view_type union; straightforward additive change
bwh_hive/bwh_hive/doctype/hive_view/hive_view.json	Appends "timeline" to the view_type Select options; additive and consistent with the frontend type change

_{Reviews (2): Last reviewed commit: "fix(timeline): parse date-only values as..." | Re-trigger Greptile}

[greptile-apps]

Unbounded DOM node count on wide date ranges

eachDayOfInterval returns one Date per day, and the render loop produces one div DOM node per entry in the header — no virtualisation. For a dataset where the earliest start_date and latest due_date span a year or more, the header alone generates 365+ nodes on every render. At 500 tasks (the query limit) covering different calendar years this is entirely realistic. Consider capping the visible window or switching to a virtual-scroll approach if performance becomes an issue.

Prompt To Fix With AI

This is a comment left during a code review.
Path: frontend/src/components/TaskTimeline.tsx
Line: 55-57

Comment:
**Unbounded DOM node count on wide date ranges**

`eachDayOfInterval` returns one `Date` per day, and the render loop produces one `div` DOM node per entry in the header — no virtualisation. For a dataset where the earliest `start_date` and latest `due_date` span a year or more, the header alone generates 365+ nodes on every render. At 500 tasks (the query limit) covering different calendar years this is entirely realistic. Consider capping the visible window or switching to a virtual-scroll approach if performance becomes an issue.

How can I resolve this? If you propose a fix, please make it concise.

[paryanineil]

Left as-is for now: the axis spans only the min/max dates of the tasks currently in view (the page filters apply first), so in practice it is weeks-to-months rather than years, and a day cell is a single lightweight div. I would rather not add virtualisation complexity pre-emptively — happy to cap the window or switch to virtual scroll in a follow-up if you would prefer it hardened now.

🤖 Addressed by Claude Code

[paryanineil]

@Rl0007 — demo video and conflicts both sorted 👇

Demo — Timeline view: bars spanning start_date → due_date on the day axis, grouped by project, horizontal scroll along the axis, and clicking a bar opening the Task Details sheet:

Conflicts — resolved. #178 (calendar) landing on develop was the cause, since the timeline touches the same view-switcher. I rebased onto the updated develop, so List / Kanban / Calendar / Timeline now coexist. The PR shows MERGEABLE again.

Also pushed fixes for the two Greptile findings (local date parsing, and reusing the existing projectMap) — details on those threads.