feat: implement full Root.unmount() with disposeFiber and instance cleanup

src/host/config.ts

@@ -2,6 +2,7 @@ import type { UNode, UElement, URoot, ComponentFn, UComponent } from "../core/sc
 import { isURoot, isUPrimitive } from "../core/schema.js";
 import { Context } from "../core/context.js";
 import type { Fiber } from "./fiber.js";
+import { disposeFiber } from "./fiber.js";
 import { reconcileProps, reconcileChildren, commitMutations } from "./reconcile.js";
 import type { CommitContext } from "./reconcile.js";
 
@@ -302,8 +303,18 @@ export function createRoot<TTag extends string, Instance, RootCtx>(
       host.emit?.("root.render", `root_${Date.now()}`, { childCount: payloadChildren.length });
     },
     unmount() {
+      const rootFiber = this.rootFiber;
+      if (!rootFiber) return;
+
+      disposeFiber(rootFiber, host as import("./fiber.js").HostLike<Instance, RootCtx>, ctx);
+
+      for (const child of rootFiber.children) {
+        host.removeChild?.(rootFiber.instance as never, child.instance as never, ctx as never);
+      }
+
       host.finalizeRoot?.(ctx);
       host.emit?.("root.unmount", `root_${Date.now()}`, {});
+      this.rootFiber = null;
     },
   };
 }

test/unmount-implementation.test.ts

@@ -0,0 +1,185 @@
+import { describe, it, expect } from "vitest";
+import { h } from "../src/core/h.js";
+import { createRoot as createHostRoot } from "../src/host/config.js";
+import type { HostConfig } from "../src/host/config.js";
+import { ReactiveRoot } from "../src/core/reactive.js";
+
+function makeHost(): {
+  host: HostConfig<string, string, Record<string, unknown>>;
+  removes: { parent: string; child: string }[];
+  finalizeInstanceCalls: string[];
+  finalizeRootCalls: { count: number };
+  emittedEvents: { type: string; id: string; payload: unknown }[];
+  instances: { tag: string; props: Record<string, unknown> }[];
+  appends: { parent: string; child: string }[];
+} {
+  const instances: { tag: string; props: Record<string, unknown> }[] = [];
+  const appends: { parent: string; child: string }[] = [];
+  const removes: { parent: string; child: string }[] = [];
+  const finalizeInstanceCalls: string[] = [];
+  const finalizeRootCalls: { count: number } = { count: 0 };
+  const emittedEvents: { type: string; id: string; payload: unknown }[] = [];
+
+  const host: HostConfig<string, string, Record<string, unknown>> = {
+    name: "test",
+    createRootContext: () => ({}),
+    createInstance: (tag, props) => {
+      const id = `${tag}_${instances.length}`;
+      instances.push({ tag, props });
+      return id;
+    },
+    createTextInstance: (text) => {
+      instances.push({ tag: "#text", props: { text } });
+      return `text_${instances.length}`;
+    },
+    appendChild: (parent, child) => {
+      appends.push({ parent, child });
+    },
+    removeChild: (parent, child) => {
+      removes.push({ parent, child });
+    },
+    finalizeInstance: (instance) => {
+      finalizeInstanceCalls.push(instance as string);
+    },
+    finalizeRoot: () => {
+      finalizeRootCalls.count++;
+    },
+    emit: (type, id, payload) => {
+      emittedEvents.push({ type, id, payload });
+    },
+  };
+  return { host, removes, finalizeInstanceCalls, finalizeRootCalls, emittedEvents, instances, appends };
+}
+
+describe("Root.unmount()", () => {
+  it("cleans up all host instances via removeChild", () => {
+    const { host, removes } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, h("span", null, "a"), h("em", null)));
+
+    root.unmount();
+
+    expect(removes.length).toBe(1);
+  });
+
+  it("clears rootFiber after unmount", () => {
+    const { host } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    expect(root.rootFiber).not.toBeNull();
+    root.unmount();
+    expect(root.rootFiber).toBeNull();
+  });
+
+  it("calls host.finalizeRoot after disposal and removal", () => {
+    const { host, finalizeRootCalls } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    expect(finalizeRootCalls.count).toBe(1);
+    root.unmount();
+    expect(finalizeRootCalls.count).toBe(2);
+  });
+
+  it("emits root.unmount event", () => {
+    const { host, emittedEvents } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    root.unmount();
+
+    const unmountEvent = emittedEvents.find((e) => e.type === "root.unmount");
+    expect(unmountEvent).toBeDefined();
+  });
+
+  it("unmount then re-render works (fresh mount)", () => {
+    const { host, instances, appends } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    const firstInstanceCount = instances.length;
+    const firstAppendCount = appends.length;
+
+    root.unmount();
+    expect(root.rootFiber).toBeNull();
+
+    root.render(h("div", null, "world"));
+    expect(root.rootFiber).not.toBeNull();
+    expect(root.rootFiber!.tag).toBe("#root");
+    expect(root.rootFiber!.children.length).toBe(1);
+    expect(root.rootFiber!.children[0]!.tag).toBe("div");
+    expect(root.rootFiber!.disposed).toBe(false);
+
+    expect(instances.length).toBeGreaterThan(firstInstanceCount);
+  });
+
+  it("double unmount is safe (idempotent)", () => {
+    const { host, removes } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    root.unmount();
+    const removesAfterFirst = removes.length;
+
+    root.unmount();
+    expect(removes.length).toBe(removesAfterFirst);
+    expect(root.rootFiber).toBeNull();
+  });
+
+  it("unmount with no prior render is safe", () => {
+    const { host, removes } = makeHost();
+    const root = createHostRoot(host, {});
+
+    root.unmount();
+    expect(root.rootFiber).toBeNull();
+    expect(removes.length).toBe(0);
+  });
+
+  it("calls finalizeInstance for each fiber", () => {
+    const { host, finalizeInstanceCalls } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, h("span", null, "a"), h("em", null)));
+
+    root.unmount();
+
+    expect(finalizeInstanceCalls.length).toBe(5);
+  });
+
+  it("signal subscriptions are cleaned up via disposeFiber", () => {
+    const disposed: string[] = [];
+    const { host } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    const rootFiber = root.rootFiber!;
+    const divFiber = rootFiber.children[0]!;
+    divFiber.signalDisposers.push(() => disposed.push("div-disposed"));
+    const textFiber = divFiber.children[0]!;
+    textFiber.signalDisposers.push(() => disposed.push("text-disposed"));
+
+    root.unmount();
+
+    expect(disposed).toContain("div-disposed");
+    expect(disposed).toContain("text-disposed");
+  });
+
+  it("does not auto-dispose ReactiveRoot — consumer responsibility", () => {
+    const { host } = makeHost();
+    const root = createHostRoot(host, {});
+    root.render(h("div", null, "hello"));
+
+    const reactiveRoot = new ReactiveRoot(h("span", null, "test"));
+    const disposeSpy: string[] = [];
+    const origDispose = reactiveRoot.dispose.bind(reactiveRoot);
+    reactiveRoot.dispose = () => {
+      disposeSpy.push("called");
+      origDispose();
+    };
+
+    root.unmount();
+
+    expect(disposeSpy.length).toBe(0);
+    expect(reactiveRoot.value).toBeDefined();
+  });
+});