test(FN-2687): add plugin install getRootDir regression coverage

- Add CLI plugin install tests that reproduce and guard the getRootDir path-resolution regression
- Validate plugin installation behavior in the regression scenario to prevent future breakage
- Add a patch changeset for @runfusion/fusion documenting the plugin install getRootDir fix

.changeset/fix-plugin-install-getrootdir.md

@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Fix plugin-install loader taskStore compatibility by ensuring CLI plugin install paths are covered with regression tests for `getRootDir` expectations.

packages/cli/src/commands/__tests__/plugin.test.ts

@@ -0,0 +1,99 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const mocks = vi.hoisted(() => {
+  const pluginStoreInstances: Array<{
+    init: ReturnType<typeof vi.fn>;
+    registerPlugin: ReturnType<typeof vi.fn>;
+    listPlugins: ReturnType<typeof vi.fn>;
+    getPlugin: ReturnType<typeof vi.fn>;
+  }> = [];
+
+  let loaderTaskStore: { getRootDir?: () => string } | undefined;
+  let loaderRootDir: string | undefined;
+
+  const PluginStore = vi.fn().mockImplementation(() => {
+    const instance = {
+      init: vi.fn().mockResolvedValue(undefined),
+      registerPlugin: vi.fn().mockResolvedValue({
+        id: "paperclip-runtime",
+        enabled: true,
+      }),
+      listPlugins: vi.fn().mockResolvedValue([]),
+      getPlugin: vi.fn(),
+    };
+    pluginStoreInstances.push(instance);
+    return instance;
+  });
+
+  const PluginLoader = vi.fn().mockImplementation((options: { taskStore: { getRootDir?: () => string } }) => {
+    loaderTaskStore = options.taskStore;
+    return {
+      loadPlugin: vi.fn().mockImplementation(async () => {
+        loaderRootDir = options.taskStore.getRootDir?.();
+      }),
+    };
+  });
+
+  return {
+    PluginStore,
+    PluginLoader,
+    pluginStoreInstances,
+    getLoaderTaskStore: () => loaderTaskStore,
+    getLoaderRootDir: () => loaderRootDir,
+    reset: () => {
+      loaderTaskStore = undefined;
+      loaderRootDir = undefined;
+      pluginStoreInstances.length = 0;
+      PluginStore.mockClear();
+      PluginLoader.mockClear();
+    },
+  };
+});
+
+vi.mock("@fusion/core", () => ({
+  PluginStore: mocks.PluginStore,
+  PluginLoader: mocks.PluginLoader,
+  validatePluginManifest: vi.fn().mockReturnValue({ valid: true, errors: [] }),
+}));
+
+vi.mock("../../project-context.js", () => ({
+  resolveProject: vi.fn().mockResolvedValue({ projectPath: "/tmp/fn-project" }),
+}));
+
+vi.mock("node:fs", () => ({
+  existsSync: vi.fn().mockReturnValue(true),
+}));
+
+vi.mock("node:fs/promises", () => ({
+  readFile: vi.fn().mockResolvedValue(
+    JSON.stringify({
+      id: "paperclip-runtime",
+      name: "Paperclip Runtime",
+      version: "1.0.0",
+    }),
+  ),
+}));
+
+import { runPluginInstall } from "../plugin.js";
+
+describe("runPluginInstall", () => {
+  beforeEach(() => {
+    mocks.reset();
+    vi.spyOn(console, "log").mockImplementation(() => {});
+    vi.spyOn(console, "error").mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("includes getRootDir on the plugin loader taskStore mock (FN-2687)", async () => {
+    await expect(runPluginInstall("/plugins/paperclip-runtime")).resolves.toBeUndefined();
+
+    const taskStore = mocks.getLoaderTaskStore();
+    expect(taskStore).toBeDefined();
+    expect(taskStore?.getRootDir).toBeTypeOf("function");
+    expect(taskStore?.getRootDir?.()).toBe("/tmp/fn-project");
+    expect(mocks.getLoaderRootDir()).toBe("/tmp/fn-project");
+  });
+});