Fix Checkbox indeterminate state

packages/core/src/components/checkbox/checkbox.tsx

@@ -1,5 +1,5 @@
 import type { JSX } from "solid-js";
-import { splitProps } from "solid-js";
+import { createEffect, splitProps } from "solid-js";
 import { createControllableSignal } from "../../primitives/create-controllable-signal";
 
 /** Represents all three states a checkbox can be in. */
@@ -37,18 +37,11 @@ export function Checkbox(props: CheckboxProps): JSX.Element {
     "children",
   ]);
 
-  const [isChecked, setChecked] = createControllableSignal<CheckedState>(
-    local.onCheckedChange
-      ? {
+  const [isChecked, setChecked] = createControllableSignal<CheckedState>({
     value: () => local.checked,
     defaultValue: () => local.defaultChecked ?? false,
     onChange: local.onCheckedChange,
-        }
-      : {
-          value: () => local.checked,
-          defaultValue: () => local.defaultChecked ?? false,
-        },
-  );
+  });
 
   const ariaChecked = (): boolean | "mixed" => {
     const c = isChecked();
@@ -87,7 +80,9 @@ export function Checkbox(props: CheckboxProps): JSX.Element {
           value={local.value ?? "on"}
           checked={isChecked() === true}
           ref={(el) => {
-            if (el) el.indeterminate = isChecked() === "indeterminate";
+            createEffect(() => {
+              el.indeterminate = isChecked() === "indeterminate";
+            });
           }}
           style={{ display: "none" }}
         />

packages/core/src/primitives/create-controllable-signal.ts

@@ -6,7 +6,7 @@ export interface CreateControllableSignalOptions<T> {
   /** Default value used when uncontrolled. Only read once at creation time — not reactive after mount. */
   defaultValue: Accessor<T>;
   /** Called whenever the value changes (both modes). */
-  onChange?: (value: T) => void;
+  onChange?: ((value: T) => void) | undefined;
 }
 
 /**