Backport state settling (#641)

Author: JoviDeCroock

.changeset/silver-crabs-sniff.md

@@ -0,0 +1,5 @@
+---
+"@preact/signals": patch
+---
+
+Change the way we deal with state settling hooks, when we know we are dealing with hooks that can settle their A -> B -> A state (and wind up at the same value). We should not verbatim rerender in our custom shouldComponentUpdate. Instead we should trust that hooks have handled their own state settling.

packages/preact/src/index.ts

@@ -328,16 +328,27 @@ Component.prototype.shouldComponentUpdate = function (
 	// 	});
 	// }
 
-	// if this component used no signals or computeds, update:
-	if (!hasSignals && !(this._updateFlags & HAS_COMPUTEDS)) return true;
-
-	// if there is a pending re-render triggered from Signals,
-	// or if there is hook or class state, update:
-	if (this._updateFlags & (HAS_PENDING_UPDATE | HAS_HOOK_STATE)) return true;
-
 	// @ts-ignore
 	for (let i in state) return true;
 
+	if (this.__f || (typeof this.u == "boolean" && this.u === true)) {
+		const hasHooksState = this._updateFlags & HAS_HOOK_STATE;
+		// if this component used no signals or computeds and no hooks state, update:
+		if (!hasSignals && !hasHooksState && !(this._updateFlags & HAS_COMPUTEDS))
+			return true;
+
+		// if there is a pending re-render triggered from Signals,
+		// or if there is hooks state, update:
+		if (this._updateFlags & HAS_PENDING_UPDATE) return true;
+	} else {
+		// if this component used no signals or computeds, update:
+		if (!hasSignals && !(this._updateFlags & HAS_COMPUTEDS)) return true;
+
+		// if there is a pending re-render triggered from Signals,
+		// or if there is hooks state, update:
+		if (this._updateFlags & (HAS_PENDING_UPDATE | HAS_HOOK_STATE)) return true;
+	}
+
 	// if any non-Signal props changed, update:
 	for (let i in props) {
 		if (i !== "__source" && props[i] !== this.props[i]) return true;

packages/preact/src/internal.d.ts

@@ -18,6 +18,11 @@ export interface AugmentedElement extends HTMLElement {
 }
 
 export interface AugmentedComponent extends Component<any, any> {
+	//  hasScuFromHooks
+	// Preact 10.12 - Preact 10.25
+	u?: boolean;
+	// Preact 10.26 and onwards
+	__f?: boolean;
 	__v: VNode;
 	_updater?: Effect;
 	_updateFlags: number;