Fix Docs undo/redo cursor restore and split reliability by hackerwins · Pull Request #164 · wafflebase/wafflebase

hackerwins · 2026-04-27T13:57:40Z

Summary

Restore cursor position after undo/redo instead of jumping to document start
Prevent undo past initial document load (avoids CRDT redo conflicts)
Replace splitLevel=2 with manual two-step split for reliable undo/redo

Details

Cursor restore: Each mutation's doc.update() now saves cursor
position to Yorkie presence with addToHistory: true. On undo/redo,
Yorkie automatically restores the pre/post-mutation cursor. The editor
reads the restored presence and calls cursor.moveTo().

Undo floor: setDocument records the undo stack depth as a floor.
canUndo() returns false at this floor, preventing users from undoing
the initial document load which causes CRDT node conflicts on redo.

Manual split: splitLevel=2 caused CRDTTreePos errors during
redo because styleByPath referenced nodes invalidated by the undo
cycle. Replaced with explicit two-step approach (delete after-text +
insert new block), matching the mergeBlock pattern. This also fixes
cross-boundary editByPath on split-created blocks.

Test plan

pnpm verify:fast passes (all tests green)
Manual: type text, Enter, type more → Ctrl+Z repeatedly → Ctrl+Y repeatedly
Manual: cursor stays at edit position after undo/redo (no jump to top)
Manual: verify split/merge in table cells still works
Manual: verify styled text split preserves styles

🤖 Generated with Claude Code

Summary by CodeRabbit

New Features
- Undo/redo operations now restore the cursor position to its location before the action.
- Cursor position is now preserved in document history for improved editing continuity.

Each mutation's doc.update() now saves cursor position to presence with addToHistory: true. This stores the pre-mutation cursor as the reverse presence, so Yorkie automatically restores it on undo. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Use getChangeID().getActorID() and getPresenceForTest() instead of accessing internal Yorkie fields via any cast. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Instead of jumping to document start (blocks[0], offset:0), the editor now reads cursor position from Yorkie presence after undo/redo. The presence is automatically restored by Yorkie's history mechanism. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

setDocument now records the undo stack depth as a floor. canUndo() returns false when the stack reaches this floor, preventing users from undoing the initial document load which causes CRDT node conflicts on subsequent redo. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

The separate doc.update() for writing pre-cursor to presence caused CRDT node conflicts during redo. Yorkie's reverse presence mechanism captures the pre-mutation presence automatically from the previousPresence snapshot, so the extra call is unnecessary. In production, updateCursorPos already keeps presence current. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

splitLevel=2 caused CRDTTreePos errors during redo because the styleByPath referenced nodes invalidated by the undo cycle. Replace with explicit two-step approach matching the mergeBlock pattern: 1. Delete text after split point from original block 2. Insert new block with the removed content This also fixes the cross-boundary editByPath bug that required the mergeByPath workaround for split-created blocks. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

coderabbitai · 2026-04-27T13:57:53Z

📝 Walkthrough

Walkthrough

This PR implements cursor position persistence into Yorkie presence linked to undo/redo history. The block-splitting mechanism transitions from native CRDT to manual two-step operations. An undo-floor prevents reverting past the initial document load, and helpers manage cursor state consumption and restoration across mutations.

Changes

Cohort / File(s)	Summary
Cursor Presence & History Integration `packages/docs/src/view/editor.ts`, `packages/frontend/src/app/docs/yorkie-doc-store.ts`	Undo/redo now restores cursor position from Yorkie presence via `getPresenceCursorPos()` with block validation and offset clamping; snapshot callbacks record cursor position via `setCursorForHistory()`. YorkieDocStore consumes `pendingCursorPos` during mutations, persists active cursor position to presence with `addToHistory: true`, and enforces an `undoFloor` to prevent undo past document load. Block splitting changed from native CRDT (`splitLevel=2`) to manual two-step split with inline reconstruction and new block insertion.
Block Merge Validation Tests `packages/frontend/tests/app/docs/merge-repro.test.ts`	New test suite validates block-merge behavior across `splitBlock`, `mergeByPath`, and `editByPath` operations using deterministic paragraph construction and tree structure inspection.
Undo/Redo History Coverage `packages/frontend/tests/app/docs/yorkie-doc-store.test.ts`	Extended test coverage for `splitBlock` undo→redo round-trips, cursor restoration via presence during undo/redo, and `deleteText`/`splitBlock` history scenarios; adjusted `canUndo/canRedo` test to reflect undo-floor semantics; added regression test (skipped) documenting redo duplication issue.

Sequence Diagram

sequenceDiagram
    actor User
    participant Editor as Editor
    participant DocStore as YorkieDocStore
    participant Presence as Yorkie<br/>Presence
    participant History as Yorkie<br/>History Stack
    
    User->>Editor: Perform edit action
    Editor->>DocStore: insertText/deleteText/splitBlock
    DocStore->>DocStore: setPendingCursorPos (position before mutation)
    DocStore->>History: doc.update(...) mutation
    History->>DocStore: Mutation applied
    DocStore->>Presence: activeCursorPos = consumedPendingCursorPos<br/>(with addToHistory: true)
    Presence->>History: Cursor position recorded in undo stack
    
    User->>Editor: Trigger Undo
    Editor->>DocStore: canUndo() check (not past undoFloor)
    DocStore->>History: Undo operation
    History->>Presence: Restore prior activeCursorPos state
    DocStore->>Editor: getPresenceCursorPos() returns restored position
    Editor->>Editor: Restore caret to block with clamped offset
    Editor->>User: Display cursor at restored position

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

Use native Yorkie Tree split/merge for concurrent convergence #126: Directly modifies splitBlock/mergeBlock logic in the same YorkieDocStore file; replaces the manual two-step split approach introduced here.
Replace snapshot-based undo/redo with Yorkie-native history in Docs #162: Both PRs introduce cursor-presence hooks and refactor undo/redo behavior in YorkieDocStore to integrate with Yorkie history.
Display remote peer cursors with name labels in docs editor #76: Both PRs enhance editor ↔ Yorkie presence cursor integration, modifying activeCursorPos presence fields and cursor publication/restoration APIs.

Poem

🐰 A cursor hops through time so deep,
With presence whispers, memories to keep,
Split blocks unite, undo's soft ground,
History anchored, no floor to bound,
Each edit saves where the carrot's found! 🥕✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately captures the main objectives of the PR: fixing undo/redo cursor restoration and improving split reliability in the document editor.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

📝 Generate docstrings

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Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch fix/docs-undo-redo-cursor-and-split

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github-actions · 2026-04-27T14:01:05Z

Verification: verify:self

Result: ✅ PASS in 124.0s

Lane	Status	Duration
sheets:build	✅ pass	12.6s
docs:build	✅ pass	8.1s
verify:fast	✅ pass	61.5s
frontend:build	✅ pass	17.2s
verify:frontend:chunks	✅ pass	0.3s
backend:build	✅ pass	4.9s
cli:build	✅ pass	1.8s
verify:entropy	✅ pass	17.6s

Verification: verify:integration

Result: ✅ PASS

codecov · 2026-04-27T14:01:33Z

Codecov Report

❌ Patch coverage is 0% with 29 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
packages/docs/src/view/editor.ts	0.00%	29 Missing ⚠️

📢 Thoughts on this report? Let us know!

hackerwins and others added 6 commits April 26, 2026 21:42

Replace private SDK access with public API

9dca57a

Use getChangeID().getActorID() and getPresenceForTest() instead of accessing internal Yorkie fields via any cast. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

hackerwins merged commit f564d04 into main Apr 27, 2026
4 checks passed

hackerwins deleted the fix/docs-undo-redo-cursor-and-split branch April 27, 2026 14:02

hackerwins mentioned this pull request May 1, 2026

Bump version to v0.3.6 #174

Merged

3 tasks

coderabbitai Bot mentioned this pull request Jul 22, 2026

Restore selection range on docs undo/redo, not just the caret #523

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3 tasks

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Fix Docs undo/redo cursor restore and split reliability#164

Fix Docs undo/redo cursor restore and split reliability#164
hackerwins merged 6 commits into
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fix/docs-undo-redo-cursor-and-split

hackerwins commented Apr 27, 2026 •

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coderabbitai Bot commented Apr 27, 2026 •

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Walkthrough

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Sequence Diagram

Estimated code review effort

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hackerwins commented Apr 27, 2026 •

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