test(daemon): retain successful PID-reuse takeover coverage (#1876)

__tests__/daemon-pid-reuse.test.ts

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+// Preserve successful PID-reuse recovery alongside the live-lock guards in #1850.
+/**
+ * Shared MCP daemon — issue #411.
+ *
+ * Validates the daemon architecture in `src/mcp/{daemon,proxy,session,index}.ts`
+ * AFTER the review fixes:
+ *
+ *   - The daemon is a *detached* background process; every `serve --mcp`
+ *     invocation is a thin proxy to it. Two invocations against one project
+ *     share ONE daemon.
+ *   - Concurrent launchers converge on a single daemon (the must-fix-1
+ *     lockfile-race: an empty-pidfile window used to let a racing candidate
+ *     delete the winner's lock → two daemons).
+ *   - Killing the launcher that spawned the daemon does NOT take the daemon
+ *     down — other attached clients keep working (the must-fix-2 detach: the
+ *     in-process daemon used to die with its launcher's process group and
+ *     orphan on host SIGKILL, regressing #277).
+ *   - A stale lockfile (dead pid) is cleared; `CODEGRAPH_NO_DAEMON=1` opts out;
+ *     the proxy refuses to attach across a version mismatch; the daemon
+ *     idle-times-out after the last client leaves (so a single session can't
+ *     leak a daemon forever).
+ *
+ * These tests intentionally spawn real `node dist/bin/codegraph.js` processes
+ * over real sockets/pipes — the same surface a Claude Code / Cursor / Codex
+ * install exercises. The daemon logs to `.codegraph/daemon.log` (it has no
+ * client stderr of its own), so daemon-side assertions read that file.
+ *
+ * `realRoot` vs `tempDir`: processes are spawned with the (possibly symlinked)
+ * `tempDir` as cwd/rootUri — on macOS `os.tmpdir()` lives under `/var`, a
+ * symlink to `/private/var`, and a spawned child's `process.cwd()` is already
+ * realpath'd. The daemon canonicalizes the root with `realpathSync`, so all
+ * path assertions use `realRoot` (the canonical form). That this matches end to
+ * end is itself the proof the canonicalization works.
+ */
+
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { ChildProcessWithoutNullStreams, spawn } from 'child_process';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { CodeGraph } from '../src';
+import { getDaemonSocketPath } from '../src/mcp/daemon-paths';
+import { CodeGraphPackageVersion } from '../src/mcp/version';
+
+const BIN = path.resolve(__dirname, '../dist/bin/codegraph.js');
+
+interface SpawnedServer {
+  child: ChildProcessWithoutNullStreams;
+  stdout: string[];
+  stderr: string[];
+}
+
+function spawnServer(cwd: string, env: NodeJS.ProcessEnv = {}): SpawnedServer {
+  const child = spawn(process.execPath, [BIN, 'serve', '--mcp'], {
+    cwd,
+    stdio: ['pipe', 'pipe', 'pipe'],
+    // #618: the daemon-attach log line is now off by default; opt the test
+    // harness into it (CODEGRAPH_MCP_LOG_ATTACH=1) so the attach assertions
+    // below can still observe a successful attach. A per-test env still wins.
+    env: { CODEGRAPH_MCP_LOG_ATTACH: '1', ...process.env, ...env },
+  }) as ChildProcessWithoutNullStreams;
+  // Swallow spawn/EPIPE errors so killing a child mid-write can't surface as an
+  // unhandled error that crashes the vitest worker.
+  child.on('error', () => { /* ignore */ });
+  child.stdin.on('error', () => { /* ignore */ });
+  const stdout: string[] = [];
+  const stderr: string[] = [];
+  let stdoutBuf = '';
+  let stderrBuf = '';
+  child.stdout.on('data', (chunk: Buffer) => {
+    stdoutBuf += chunk.toString('utf8');
+    let idx: number;
+    while ((idx = stdoutBuf.indexOf('\n')) !== -1) {
+      stdout.push(stdoutBuf.slice(0, idx));
+      stdoutBuf = stdoutBuf.slice(idx + 1);
+    }
+  });
+  child.stderr.on('data', (chunk: Buffer) => {
+    stderrBuf += chunk.toString('utf8');
+    let idx: number;
+    while ((idx = stderrBuf.indexOf('\n')) !== -1) {
+      stderr.push(stderrBuf.slice(0, idx));
+      stderrBuf = stderrBuf.slice(idx + 1);
+    }
+  });
+  return { child, stdout, stderr };
+}
+
+function sendMessage(child: ChildProcessWithoutNullStreams, msg: unknown): void {
+  try { child.stdin.write(JSON.stringify(msg) + '\n'); } catch { /* child may be gone */ }
+}
+
+function sendInitialize(child: ChildProcessWithoutNullStreams, rootUri: string, id: number): void {
+  sendMessage(child, {
+    jsonrpc: '2.0',
+    id,
+    method: 'initialize',
+    params: {
+      protocolVersion: '2024-11-05',
+      capabilities: {},
+      clientInfo: { name: 'test', version: '0.0.0' },
+      rootUri,
+    },
+  });
+}
+
+/** Find a JSON-RPC response with the given id (result OR error) on stdout. */
+function findResponse(stdout: string[], id: number): any | null {
+  for (const line of stdout) {
+    if (!line.trim()) continue;
+    try {
+      const parsed = JSON.parse(line);
+      if (parsed && parsed.id === id && (parsed.result !== undefined || parsed.error !== undefined)) {
+        return parsed;
+      }
+    } catch { /* not JSON */ }
+  }
+  return null;
+}
+
+function waitFor<T>(
+  predicate: () => T | undefined | null | false,
+  timeoutMs: number,
+  pollMs = 25,
+  label = '',
+): Promise<T> {
+  return new Promise((resolve, reject) => {
+    const started = Date.now();
+    const tick = () => {
+      let v: T | undefined | null | false;
+      try { v = predicate(); } catch (e) { return reject(e); }
+      if (v) return resolve(v as T);
+      if (Date.now() - started > timeoutMs) {
+        // Name the wait: an async stack loses the await site, so an unlabeled
+        // timeout can't tell WHICH step flaked (the #662 test's recurring
+        // timeout was undiagnosable for exactly this reason).
+        return reject(new Error(`Timed out after ${timeoutMs}ms${label ? ` waiting for: ${label}` : ''}`));
+      }
+      setTimeout(tick, pollMs);
+    };
+    tick();
+  });
+}
+
+function isAlive(pid: number): boolean {
+  try { process.kill(pid, 0); return true; } catch { return false; }
+}
+
+function readLockPid(root: string): number | null {
+  try {
+    const raw = fs.readFileSync(path.join(root, '.codegraph', 'daemon.pid'), 'utf8');
+    const info = JSON.parse(raw);
+    return typeof info.pid === 'number' ? info.pid : null;
+  } catch { return null; }
+}
+
+function readDaemonLog(root: string): string {
+  try { return fs.readFileSync(path.join(root, '.codegraph', 'daemon.log'), 'utf8'); }
+  catch { return ''; }
+}
+
+function countListeningLines(root: string): number {
+  return readDaemonLog(root).split('\n').filter((l) => l.includes('[CodeGraph daemon] Listening on')).length;
+}
+
+function killTree(...procs: ChildProcessWithoutNullStreams[]): void {
+  for (const p of procs) {
+    if (!p.killed) { try { p.kill('SIGKILL'); } catch { /* gone */ } }
+  }
+}
+
+async function waitProcessExit(pid: number, timeoutMs: number): Promise<boolean> {
+  return waitFor(() => !isAlive(pid), timeoutMs).then(() => true).catch(() => false);
+}
+
+describe('Shared MCP daemon (issue #411)', () => {
+  let tempDir: string;   // the (possibly symlinked) path processes are spawned with
+  let realRoot: string;  // its canonical form — what the daemon keys paths on
+  const servers: SpawnedServer[] = [];
+
+  beforeEach(async () => {
+    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-mcp-daemon-'));
+    const cg = await CodeGraph.init(tempDir);
+    cg.close();
+    realRoot = fs.realpathSync(tempDir);
+  });
+
+  afterEach(async () => {
+    killTree(...servers.map((s) => s.child));
+    // The daemon is detached (not a tracked child) — reap it explicitly via the
+    // pid it recorded, so a test can't leak a background daemon. Guard against
+    // our own pid: the version-mismatch test plants `pid: process.pid` in the
+    // lockfile, and we must never SIGKILL the vitest worker.
+    const daemonPid = readLockPid(realRoot);
+    if (daemonPid && daemonPid !== process.pid && isAlive(daemonPid)) {
+      try { process.kill(daemonPid, 'SIGKILL'); } catch { /* race */ }
+    }
+    await new Promise((r) => setTimeout(r, 50));
+    servers.length = 0;
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  });
+
+  it('takes over after SIGKILL even when the stale PID has been reused (#1553)', async () => {
+    const env = { CODEGRAPH_DAEMON_IDLE_TIMEOUT_MS: '30000' };
+    const first = spawnServer(tempDir, env);
+    servers.push(first);
+    sendInitialize(first.child, `file://${tempDir}`, 1);
+    await waitFor(() => findResponse(first.stdout, 1), 10000);
+    await waitFor(() => countListeningLines(realRoot) >= 1, 10000);
+    const killedPid = readLockPid(realRoot)!;
+
+    process.kill(killedPid, 'SIGKILL');
+    expect(await waitProcessExit(killedPid, 8000)).toBe(true);
+
+    // Model OS PID reuse without risking another process: the stale lock now
+    // names this live vitest worker, but no daemon answers the leftover socket.
+    fs.writeFileSync(
+      path.join(realRoot, '.codegraph', 'daemon.pid'),
+      JSON.stringify({
+        pid: process.pid,
+        version: CodeGraphPackageVersion,
+        socketPath: getDaemonSocketPath(realRoot),
+        startedAt: Date.now() - 60_000,
+      }),
+    );
+
+    const second = spawnServer(tempDir, env);
+    servers.push(second);
+    sendInitialize(second.child, `file://${tempDir}`, 2);
+    const response = await waitFor(() => findResponse(second.stdout, 2), 12000);
+    expect(response.result.serverInfo.name).toBe('codegraph');
+    await waitFor(() => countListeningLines(realRoot) >= 2, 10000);
+
+    const replacementPid = readLockPid(realRoot)!;
+    expect(replacementPid).not.toBe(killedPid);
+    expect(replacementPid).not.toBe(process.pid);
+    expect(isAlive(replacementPid)).toBe(true);
+    expect(isAlive(process.pid)).toBe(true);
+  }, 50000);
+
+});