Grid-native CellEditing core: a logical session projected into pooled cells

Sub of #18762 — the session/projection core, with the minimal complete edit loop. Graduated from D#17832 (OQ1–OQ7 dispositions, OQ1 spike).

Context

Neo.grid.plugin.CellEditing extends Neo.table.plugin.CellEditing and mounts no editor by any gesture. Measured at dev@d688710175 on a grid with cellEditing: true and a CellModel: double-click, click+Enter and F2 mount nothing, and double-click throws Cannot read properties of null (reading 'vdom').

D#17832's OQ1 spike, on the same head, prototyped the target shape against a 40-column / 400-row grid with locked-start and locked-end columns: a View-owned session whose editor the rendering Row embeds into the proving cell. Double-click and F2 embodied a focused editor in pooled and locked cells; an in-range horizontal remap kept embodiment and focus; leaving the row pool or the column window removed it; returning reprojected it with the App-Worker draft intact; Enter committed and Escape cancelled. Zero page errors.

It also measured two defects that break the loop on common input:

1. Home, End, PageUp and PageDown pressed inside the editor scroll grid.View, at either caret position (Chromium, macOS key bindings). End scrolled 98 → 12081 and PageDown one page, recycling the proving row mid-typing; Home and PageUp scrolled 160 → 0. ArrowUp/ArrowDown are consumed by the input. On Linux key bindings Home/End move the caret instead, so PageUp/PageDown are the cross-platform red.
2. A pointer click inside the embodied editor hands DOM focus to grid.View. grid.Body#onRowClick (src/grid/Body.mjs:1219) focuses the View for every click inside a row.

The Problem

The inherited lifecycle cannot be patched into shape (D#17832 Reflective Pause): it resolves a cell with body.getCellId(record, dataField) against Grid's (rowIndex, dataField) signature, assumes the center body, registers keys on owner.body.keys — never on a key event's path while focus lives on grid.View — reads neo-selected from the focused element, and unmounts through body.createRow, which grid.Body lacks. Two fixes that kept the inheritance were dropped (#17935/PR #17937, #18217/PR #18222).

The Architectural Reality

The Fix

• Neo.grid.plugin.CellEditing extends Neo.plugin.Base, keeps its class name and ntype, and owns one session {recordId, dataField, editor, generation}. It registers Enter/F2/Escape on grid.View's keys and removes them on destroy.
• The Row embeds the session's editor in applyRendererOutput for the cell proving {recordId, dataField}, in the pooled and permanent passes, and sets the editor's parent to itself — so unmountRemovedChildren tracks projection loss and the next render reprojects. Starting and ending a session repaints only the rows that render the record.
• Terminals: Enter commits a valid dirty value to the record; Escape cancels; focus leaving the grid commits-if-valid; activating another cell commits-if-valid first; each ends with DOM focus on grid.View. Projection loss is classified from the logical resolver — is the record in a row pool and the column in the mounted window — never from message timing.
• grid.column.Base declares editable_ (reactive) and editor. Turning editable off ends an active session on that column.
• Defect 1: DomEvents#onKeyDown stops a navigation key pressed inside a neo-grid-editor from scrolling, keeping the platform's caret semantics for Home/End.
• Defect 2: a pointer gesture inside .neo-grid-editor neither focuses the View nor changes the cell selection.
• Anchor & Echo JSDoc on the plugin, the Row seam and the new column configs; regenerate docs/output/class-hierarchy.json.

Contract Ledger

Acceptance Criteria

• AC-1 — src/grid/plugin/CellEditing.mjs extends Neo.plugin.Base; nothing under src/grid/ imports src/table/plugin/CellEditing.mjs, which is unchanged.
• AC-2 — double-click, Enter and F2 on an editable cell in the center, locked-start and locked-end bodies embody one editor in that cell with DOM focus in its input; Space starts no edit; an editable: false column embodies nothing.
• AC-3 — Enter writes a valid dirty value to the record; Escape leaves the record unchanged; an invalid value blocks Enter and keeps the editor focused; commit and cancel remove the embodiment, destroy the editor and return DOM focus to grid.View.
• AC-4 — with a typed draft: an in-range horizontal remap keeps embodiment and focus; the column leaving the mounted window, or the record leaving the row pool, removes the embodiment without committing or cancelling; returning reprojects it with the draft. At no point does any cell show the editor for another record or dataField.
• AC-5 — activating another cell commits-if-valid, then embodies the new target; focus leaving the grid commits-if-valid; exactly one .neo-grid-editor exists in the grid at any time.
• AC-6 — setting a column's editable to false while its session is active cancels that session.
• AC-7 — PageUp and PageDown pressed inside the editor do not move grid.View's scroll position (red on dev); where the platform binds Home/End to scrolling, neither do they; where it binds them to the caret, the caret still moves.
• AC-8 — a click inside the embodied editor keeps DOM focus in its input and leaves the cell selection unchanged — red against the new plugin without the onRowClick exemption.
• AC-9 — destroying the grid, or the plugin, destroys an active editor and removes the plugin's View keys; no page error in any arm.
• AC-10 — coverage CI executes: a components-tier spec for AC-2, 3, 5, 6, 8, 9 and a Brain-free e2e spec (no neuralLink token) on a high-cardinality fixture for AC-2's bodies, AC-4 and AC-7 — each arm red-first where the defect exists on dev, and node buildScripts/util/e2eCiSelection.mjs --coverage-line counting the new e2e file.

Out of Scope

Tab/Shift+Tab traversal and the suspended-Tab pre-registration · picker editors, the interaction island and two-stage Escape · GestureClaimArbiter ordering · restoring DOM focus on reprojection · aria-readonly and live announcement of invalid state · the S3 opt-out · the IME probe · examples/grid/cellEditing (its renderer-scope crash), the Grids guide, the Table control · Table editing.

Avoided Traps

• Hooks on the Table plugin or a getCellId shim — PR #18222's shape; keeps the forbidden inheritance load-bearing.
• Mounting the editor by mutating a found cell's vdom — the inherited approach; the next Row render drops it, and a pool slot then carries it for another record.
• Classifying projection loss by waiting for the focus manager's focusLeave timing — the spike saw both orders; the logical resolver is deterministic.
• A Neural Link whitebox spec as the proof — deselected in CI by buildScripts/util/e2eCiSelection.mjs.
• Suppressing Home/End unconditionally — breaks caret movement on platforms that bind them to the caret.

Decision Record

Discussion-origin: NOT_NEEDED. Impact: none.

Discussion Criteria Mapping

OQ1 → AC-2, AC-4 · OQ2 (S2 default, the scroll-away defect) → AC-4, AC-7 · OQ3 → AC-2 · OQ4 → AC-2, AC-5 · OQ5 (Enter, Escape, focus leaving the grid, activating another cell, the pointer defect) → AC-3, AC-5, AC-8 · OQ6 → AC-3, AC-5 · OQ7 → AC-1

Related

#18762 (parent) · D#17832 · #6168 (completion claim superseded) · #17935 · #18217 · PR #17937 · PR #18222 (salvage fixtures: test/playwright/component/apps/grid-cell-editing/, needs viewConfig) · #18626 (View-owned selection model)

Live latest-open sweep: latest 20 open issues at 2026-09-16T08:30Z; no equivalent. A2A claim sweep: no claim on grid cell editing. Memory Core rationale sweep: D#17832's authoring and fold sessions; nothing contradicts this leaf. Own-assignment sweep: nothing on grid editing.

Origin Session ID: a758f0e1-0dc1-4e4e-a975-4824a9319487

Retrieval Hint: "grid CellEditing render-time projection Row applyRendererOutput session pooled cells editable_ DomEvents scroll keys"