fix(app): start MCP servers only for open directories (#28937)

packages/app/src/utils/refcount.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, test } from "bun:test"
+import { createRoot } from "solid-js"
+import { createRefCountMap } from "./refcount"
+import { pathKey } from "./path-key"
+
+describe("createRefCountMap", () => {
+  test("removes an item after its last owner is disposed", () => {
+    const removed: string[] = []
+    const map = createRefCountMap(
+      (key) => key,
+      (key) => removed.push(key),
+    )
+    const first = createRoot((dispose) => {
+      map("/project")
+      return dispose
+    })
+    const second = createRoot((dispose) => {
+      map("/project")
+      return dispose
+    })
+
+    first()
+    expect(removed).toEqual([])
+    second()
+    expect(removed).toEqual(["/project"])
+  })
+
+  test("keeps equivalent path consumers until the last owner is disposed", () => {
+    const removed: string[] = []
+    const map = createRefCountMap(
+      (key) => key,
+      (key) => removed.push(key),
+      pathKey,
+    )
+    const first = createRoot((dispose) => {
+      map("C:\\repo")
+      return dispose
+    })
+    const second = createRoot((dispose) => {
+      map("C:/repo/")
+      return dispose
+    })
+
+    first()
+    expect(removed).toEqual([])
+    second()
+    expect(removed).toEqual(["C:/repo"])
+  })
+})

packages/app/src/utils/refcount.ts

@@ -1,26 +1,32 @@
 import { onCleanup } from "solid-js"
 
-export function createRefCountMap<T>(create: (key: string) => T) {
+export function createRefCountMap<T>(
+  create: (key: string) => T,
+  remove?: (key: string) => void,
+  identity: (key: string) => string = (key) => key,
+) {
   const items = new Map<string, T>()
   const refCounts = new Map<string, number>()
 
   return (key: string) => {
+    const id = identity(key)
     onCleanup(() => {
-      refCounts.set(key, (refCounts.get(key) ?? 0) - 1)
-      if (refCounts.get(key) === 0) {
-        items.delete(key)
-        refCounts.delete(key)
+      refCounts.set(id, (refCounts.get(id) ?? 0) - 1)
+      if (refCounts.get(id) === 0) {
+        remove?.(id)
+        items.delete(id)
+        refCounts.delete(id)
       }
     })
 
-    const cached = items.get(key)
+    const cached = items.get(id)
     if (cached) {
-      refCounts.set(key, (refCounts.get(key) ?? 0) + 1)
+      refCounts.set(id, (refCounts.get(id) ?? 0) + 1)
       return cached
     }
     const item = create(key)
-    items.set(key, item)
-    refCounts.set(key, 1)
+    items.set(id, item)
+    refCounts.set(id, 1)
     return item
   }
 }