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* @file transaction.js
* @description Trace hooks for Avenx Rewind.
*
* A value that changes back on its own is the single most confusing thing a
* trace can contain. Without a node for it, a rewind shows up as a run of
* writes with no cause — exactly the situation Trace exists to eliminate.
*
* The node is opened *around* the rewind, so every restoring write lands
* underneath it as an ordinary write and the causal tree reads:
*
* ▸ click <button.qty-inc> CartItem
* └─ action CartItem.incQty()
* └─ rewind CartItem.incQty — 3 restored [safe]
* ├─ write cart.items.0.qty 2 → 1
* └─ write CartItem.busy true → false
*
* Kept out of `journal.js` for the same reason `trace/reactive.js` is kept out
* of `proxyHandler.js`: the reactive system should not import the recorder.
* @module lib/core/trace/transaction
*/
import { tracer } from './tracer.js';
import { TraceNodeType } from './schema.js';
/**
* Opens a rewind node and makes it the causal parent of the restoring writes.
*
* Callers must guard with `tracer.on` and pass the returned token to
* `tracer.leave()` in a `finally`.
* @param {object} frame - The journal frame about to be played backwards.
* @returns {{token: number, id: number|null}} The restore token for
* `tracer.leave`, and the node's id so the outcome can be filled in later.
* `{token: -1, id: null}` when tracing is off.
*/
export function traceRewindStart(frame) {
if (!tracer.sink) {
return { token: -1, id: null };
}
const token = tracer.enter(TraceNodeType.REWIND, {
action: frame.owner ? `${frame.owner}.${frame.name}` : frame.name,
policy: frame.onConflict,
// Filled in by `traceRewindOutcome` once the rewind has run: the counts
// are not known until it has, and the node has to exist first so the
// restoring writes are recorded underneath it.
restored: 0,
conflicts: 0,
});
return { token, id: tracer.current() };
}
/**
* Records what the rewind managed to do, on the node opened for it.
* @param {number|null} id - The node id `traceRewindStart` returned.
* @param {object} outcome - What `JournalFrame#rewind` reported.
* @returns {void}
*/
export function traceRewindOutcome(id, outcome) {
if (id === null || !tracer.sink || typeof tracer.sink.annotate !== 'function') {
return;
}
tracer.sink.annotate(id, {
restored: outcome.restored,
conflicts: outcome.conflicts.length,
...(outcome.conflicts.length > 0
? { conflictPaths: outcome.conflicts.map((conflict) => conflict.path) }
: {}),
...(outcome.unrewindable.length > 0 ? { unrewindable: outcome.unrewindable } : {}),
});
}
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