fix: delete from batch_values on updates

packages/svelte/src/internal/client/reactivity/batch.js

@@ -286,11 +286,12 @@ export class Batch {
 			this.previous.set(source, value);
 		}
 
-		// Don't save errors in `batch_values`, or they won't be thrown in `runtime.js#get`
 		if ((source.f & ERROR_VALUE) === 0) {
 			this.current.set(source, source.v);
-			batch_values?.set(source, source.v);
 		}
+
+		// The value is now the newest known value for this source, therefore remove it from batch_values
+		batch_values?.delete(source);
 	}
 
 	activate() {

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -365,8 +365,20 @@ export function update_derived(derived) {
 		return;
 	}
 
+	// During time traveling we don't want to reset the status so that
+	// traversal of the graph in the other batches still happens
 	if (batch_values !== null) {
-		batch_values.set(derived, derived.v);
+		// Delete the value as the current one is now the latest.
+		// Deleting instead of updating handles the case where a derived
+		// is subsequently indirectly updated in the same batch — without
+		// deleting here we would incorrectly get the old value from `batch_values`
+		// instead of recomputing it. The one drawback is that it's now a bit
+		// more inefficient to get the value of that derived again in the same batch,
+		// as it has to check is_dirty all the way up the graph all the time.
+		// TODO if that turns out to be a performance problem, we could try
+		// to save the current status of the derived in a map and restore it
+		// before leaving the batch.
+		batch_values.delete(derived);
 	} else {
 		var status = (derived.f & CONNECTED) === 0 ? MAYBE_DIRTY : CLEAN;
 		set_signal_status(derived, status);

packages/svelte/src/internal/client/runtime.js

@@ -179,7 +179,12 @@ export function is_dirty(reaction) {
 			}
 		}
 
-		if ((flags & CONNECTED) !== 0) {
+		if (
+			(flags & CONNECTED) !== 0 &&
+			// During time traveling we don't want to reset the status so that
+			// traversal of the graph in the other batches still happens
+			batch_values === null
+		) {
 			set_signal_status(reaction, CLEAN);
 		}
 	}
@@ -611,25 +616,15 @@ export function get(signal) {
 	} else if (is_derived) {
 		derived = /** @type {Derived} */ (signal);
 
-		var should_reconnect = is_updating_effect && effect_tracking() && (derived.f & CONNECTED) === 0;
-
 		if (batch_values?.has(derived)) {
-			// This happens as part of is_dirty normally, but we return early
-			// here so we need to do it separately
-			remove_marked_flag(derived);
-
-			if (should_reconnect) {
-				reconnect(derived);
-			}
-
 			return batch_values.get(derived);
 		}
 
 		if (is_dirty(derived)) {
 			update_derived(derived);
 		}
 
-		if (should_reconnect) {
+		if (is_updating_effect && effect_tracking() && (derived.f & CONNECTED) === 0) {
 			reconnect(derived);
 		}
 	} else if (batch_values?.has(signal)) {
@@ -662,23 +657,6 @@ function reconnect(derived) {
 	}
 }
 
-/**
- * Removes the WAS_MARKED flag from the derived and its dependencies
- * @param {Value} derived
- */
-function remove_marked_flag(derived) {
-	// We cannot stop at the first non-marked derived because batch_values can
-	// cause "holes" of unmarked deriveds in an otherwise marked graph
-	if ((derived.f & DERIVED) === 0) return;
-
-	derived.f &= ~WAS_MARKED;
-
-	// Only deriveds with dependencies can be marked
-	for (const dep of /** @type {Value[]} */ (/** @type {Derived} */ (derived).deps)) {
-		remove_marked_flag(dep);
-	}
-}
-
 /** @param {Derived} derived */
 function depends_on_old_values(derived) {
 	if (derived.v === UNINITIALIZED) return true; // we don't know, so assume the worst

packages/svelte/tests/runtime-runes/samples/async-derived-in-multiple-effects/_config.js

@@ -7,12 +7,10 @@ export default test({
 
 		button?.click();
 		await tick();
-		// TODO this is wrong: it should be [5]
-		assert.deepEqual(logs, [4]);
+		assert.deepEqual(logs, [5]);
 
 		button?.click();
 		await tick();
-		// TODO this is wrong: it should be [5, 7]
-		assert.deepEqual(logs, [4, 7]);
+		assert.deepEqual(logs, [5, 7]);
 	}
 });