feat: add plan mode with enter/exit tools (#8281)

packages/opencode/test/util/lock.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, test } from "bun:test"
+import { Lock } from "../../src/util/lock"
+
+function tick() {
+  return new Promise<void>((r) => queueMicrotask(r))
+}
+
+async function flush(n = 5) {
+  for (let i = 0; i < n; i++) await tick()
+}
+
+describe("util.lock", () => {
+  test("writer exclusivity: blocks reads and other writes while held", async () => {
+    const key = "lock:" + Math.random().toString(36).slice(2)
+
+    const state = {
+      writer2: false,
+      reader: false,
+      writers: 0,
+    }
+
+    // Acquire writer1
+    using writer1 = await Lock.write(key)
+    state.writers++
+    expect(state.writers).toBe(1)
+
+    // Start writer2 candidate (should block)
+    const writer2Task = (async () => {
+      const w = await Lock.write(key)
+      state.writers++
+      expect(state.writers).toBe(1)
+      state.writer2 = true
+      // Hold for a tick so reader cannot slip in
+      await tick()
+      return w
+    })()
+
+    // Start reader candidate (should block)
+    const readerTask = (async () => {
+      const r = await Lock.read(key)
+      state.reader = true
+      return r
+    })()
+
+    // Flush microtasks and assert neither acquired
+    await flush()
+    expect(state.writer2).toBe(false)
+    expect(state.reader).toBe(false)
+
+    // Release writer1
+    writer1[Symbol.dispose]()
+    state.writers--
+
+    // writer2 should acquire next
+    const writer2 = await writer2Task
+    expect(state.writer2).toBe(true)
+
+    // Reader still blocked while writer2 held
+    await flush()
+    expect(state.reader).toBe(false)
+
+    // Release writer2
+    writer2[Symbol.dispose]()
+    state.writers--
+
+    // Reader should now acquire
+    const reader = await readerTask
+    expect(state.reader).toBe(true)
+
+    reader[Symbol.dispose]()
+  })
+})