fix(hierarchy): let the hierarchy tab be closed

The Hierarchy tool window's content tab had no close button, so a type or
call hierarchy stayed until another one replaced it. The tab is closable
now; closing it clears the tree and hides the tool window, which has no
other content.

Refs #2471

src/features/code-insight/HierarchyView.tsx

@@ -17,6 +17,7 @@ import {
 } from "@/ui";
 import { openLocation } from "./ipc";
 import {
+  closeHierarchy,
   ROOT_ID,
   directionLabel,
   hierarchyTitle,
@@ -64,9 +65,10 @@ export function HierarchyTabs() {
       variant="compact"
       className={styles.tabs}
       aria-label="Hierarchies"
-      items={[{ id: "current", label }]}
+      items={[{ id: "current", label, closable: true }]}
       activeId="current"
       onSelect={() => undefined}
+      onClose={closeHierarchy}
     />
   );
 }

src/features/code-insight/hierarchy.test.ts

@@ -2,9 +2,10 @@ import { describe, expect, it, vi } from "vitest";
 import type { HierarchyItem, OutlineItem, ReferencesIncomplete, SymbolKind } from "@/bindings";
 
 const hint = vi.fn();
+const hide = vi.hoisted(() => vi.fn());
 vi.mock("@/workbench/contributions", async (orig) => ({
   ...(await orig<typeof import("@/workbench/contributions")>()),
-  toolWindowService: () => ({ show: () => undefined }),
+  toolWindowService: () => ({ show: () => undefined, hide }),
 }));
 
 const range = (l1: number, c1: number, l2: number, c2: number) => ({
@@ -167,3 +168,13 @@ describe("hierarchy", () => {
     }
   });
 });
+
+describe("closing the hierarchy tab", () => {
+  it("clears the tree and hides the tool window", async () => {
+    const { closeHierarchy, useHierarchy } = await import("./hierarchy");
+    useHierarchy.setState({ root: { name: "Number", path: "/p/Number.java", line: 0, col: 0 } as never });
+    closeHierarchy();
+    expect(useHierarchy.getState().root).toBeNull();
+    expect(hide).toHaveBeenCalledWith("hierarchy");
+  });
+});

src/features/code-insight/hierarchy.ts

@@ -73,6 +73,12 @@ export function resetHierarchy() {
   }));
 }
 
+/** Closes the hierarchy's content tab; with no content left the tool window hides. */
+export function closeHierarchy() {
+  resetHierarchy();
+  toolWindowService().hide("hierarchy");
+}
+
 /** The empty-result line of the hierarchy tree. */
 export function noneFoundLabel(mode: HierarchyMode, direction: HierarchyDirection): string {
   if (mode === "call") return direction === "incoming" ? tx`— no callers found` : tx`— no callees found`;