deepseek-harness/examples/acp-agent/tests/snapshot-harness.ts

/**
 * Shared harness for the ACP snapshot tests. A plain module (NOT a *.spec.ts /
 * *.snapshot.ts) so importing it never re-registers another file's tests.
 *
 * It boots the REAL examples/acp-agent subprocess via the cordis Loader (so the
 * export-shape bug class stays guarded — see docs/postmortem/0001), drives it
 * over real ACP JSON-RPC stdio with a deterministic input script, tees raw
 * stdout (for the golden + a purity check) into an SDK `ClientSideConnection`,
 * and — in record mode — harvests the persisted session JSONL after a graceful
 * shutdown flush. Two pure normalizers turn the captured stdout frames and the
 * session-log events into stable, snapshot-able text.
 *
 * See docs/rfc/implemented/2026-06-19-acp-snapshot-tests.md.
 */

import { spawn, type ChildProcessWithoutNullStreams } from 'node:child_process'
import { mkdtemp, readFile, readdir, rm } from 'node:fs/promises'
import { tmpdir } from 'node:os'
import { join } from 'node:path'
import { fileURLToPath } from 'node:url'
import { Readable, Writable } from 'node:stream'
import {
  ClientSideConnection,
  ndJsonStream,
  PROTOCOL_VERSION,
  type Agent as AcpAgent,
  type Client,
  type RequestPermissionRequest,
  type RequestPermissionResponse,
  type SessionNotification,
} from '@agentclientprotocol/sdk'

const startScript = fileURLToPath(new URL('../start.ts', import.meta.url))
const tsxLoader = fileURLToPath(import.meta.resolve('tsx'))
// The repo-root tsconfig: dev/test run UNBUILT and the `@deepseek-ai/dsh-*`
// imports resolve through its `paths` map. The child's cwd is a temp dir
// OUTSIDE the repo, so tsx's upward search would miss it — point tsx at the
// repo tsconfig explicitly (same fix the e2e harness uses). Repo root is four
// levels up from this file (examples/acp-agent/tests).
const repoTsconfig = fileURLToPath(new URL('../../../tsconfig.json', import.meta.url))

/**
 * One step of a scenario's deterministic input script (`input.json`). The
 * harness interprets these in order. `newSession` captures the server-issued
 * (random) session id into a `{{sessionId}}` variable that later steps
 * reference, since a committed file cannot know the id in advance.
 */
type InputStep =
  | { op: 'initialize'; terminalOutput?: boolean }
  | { op: 'newSession' }
  | { op: 'prompt'; text: string }
  | { op: 'cancel' }

/** A scenario's `input.json`: an ordered list of input steps. */
export interface InputScript {
  steps: InputStep[]
}

/** The result of running a scenario: raw stdout + the harvested session log. */
export interface RunResult {
  /** Raw stdout bytes (decoded utf8), every newline-delimited JSON-RPC frame. */
  rawStdout: string
  /** stderr (for diagnostics on failure). */
  stderr: string
  /** The session id the server issued (undefined if no session was created). */
  sessionId?: string
  /** The temp cwd the session ran in (the bash workspace). */
  cwd: string
  /** The persisted session log's content, if one was produced. */
  sessionLog?: string
}

interface RunOptions {
  /** `replay` (default, keyless) or `record` (real API, harvests the log). */
  mode: 'replay' | 'record'
  /** The recorded session JSONL fixture path (replay reads it; record writes near it). */
  fixtureFile: string
  /** Optional sidecar override path (replay). */
  overrideFile?: string
}

/**
 * Run a scenario end-to-end against a freshly-spawned subprocess. Owns the
 * child and its temp dirs; always tears them down. Returns the captured stdout
 * and (record mode) the harvested session-log path.
 */
export async function runScenario(input: InputScript, opts: RunOptions): Promise<RunResult> {
  const cwd = await mkdtemp(join(tmpdir(), 'acp-snap-cwd-'))
  const sessionsRoot = await mkdtemp(join(tmpdir(), 'acp-snap-sessions-'))
  const env: NodeJS.ProcessEnv = {
    ...process.env,
    TSX_TSCONFIG_PATH: repoTsconfig,
    DSH_SNAPSHOT: opts.mode,
    DSH_SNAPSHOT_FILE: opts.fixtureFile,
    DSH_SNAPSHOT_SESSIONS_ROOT: sessionsRoot,
    ...opts.overrideFile !== undefined ? { DSH_SNAPSHOT_OVERRIDE: opts.overrideFile } : {},
  }

  const child: ChildProcessWithoutNullStreams = spawn(
    process.execPath,
    ['--import', tsxLoader, startScript],
    { cwd, env, stdio: ['pipe', 'pipe', 'pipe'] },
  )

  const rawBuffers: Buffer[] = []
  const stderrChunks: string[] = []
  child.stderr.setEncoding('utf8')
  child.stderr.on('data', (c: string) => stderrChunks.push(c))

  // Tee raw stdout: accumulate the bytes for the golden + purity check, and ALSO
  // feed the same bytes to the SDK client through a passthrough. Buffer the raw
  // bytes (not per-chunk utf8 strings) and decode once at the end, so a
  // multibyte sequence split across two 'data' events can't corrupt the golden.
  const passthrough = new Readable({ read() {} })
  child.stdout.on('data', (buf: Buffer) => {
    rawBuffers.push(buf)
    passthrough.push(buf)
  })
  child.stdout.on('end', () => passthrough.push(null))

  const stream = ndJsonStream(
    Writable.toWeb(child.stdin) as WritableStream<Uint8Array>,
    Readable.toWeb(passthrough) as ReadableStream<Uint8Array>,
  )
  const makeClient = (_agent: AcpAgent): Client => ({
    sessionUpdate(_params: SessionNotification): Promise<void> {
      return Promise.resolve()
    },
    requestPermission(_params: RequestPermissionRequest): Promise<RequestPermissionResponse> {
      return Promise.resolve({ outcome: { outcome: 'cancelled' } })
    },
  })
  const client = new ClientSideConnection(makeClient, stream)

  let sessionId: string | undefined
  let sessionLog: string | undefined
  try {
    for (const step of input.steps) {
      await runStep(client, step, cwd, () => sessionId, (id) => { sessionId = id })
    }
    // Done driving: close stdin so the server disposes gracefully (flushing
    // persistence) and exits. Then await exit so the harvested log is complete.
    child.stdin.end()
    await waitForExit(child)
    // Harvest the persisted log (if any) while the temp dirs still exist.
    const sessionLogPath = await findSessionLog(sessionsRoot)
    if (sessionLogPath !== undefined) sessionLog = await readFile(sessionLogPath, 'utf8')
  } finally {
    // Failure-safe teardown: kill a still-running child and drop the temp dirs
    // even if a step/harvest threw, so a flaky run never leaks a process or dir.
    if (child.exitCode === null && child.signalCode === null) {
      child.kill('SIGKILL')
      await waitForExit(child)
    }
    await rm(cwd, { recursive: true, force: true })
    await rm(sessionsRoot, { recursive: true, force: true })
  }

  return {
    rawStdout: Buffer.concat(rawBuffers).toString('utf8'),
    stderr: stderrChunks.join(''),
    cwd,
    ...sessionId !== undefined ? { sessionId } : {},
    ...sessionLog !== undefined ? { sessionLog } : {},
  }
}

/** Drive one input step over the client connection. */
async function runStep(
  client: ClientSideConnection,
  step: InputStep,
  cwd: string,
  getSessionId: () => string | undefined,
  setSessionId: (id: string) => void,
): Promise<void> {
  switch (step.op) {
    case 'initialize':
      await client.initialize({
        protocolVersion: PROTOCOL_VERSION,
        clientCapabilities: step.terminalOutput === true ? { _meta: { terminal_output: true } } : {},
      })
      return
    case 'newSession': {
      const { sessionId } = await client.newSession({ cwd, mcpServers: [] })
      setSessionId(sessionId)
      return
    }
    case 'prompt': {
      const sessionId = getSessionId()
      if (sessionId === undefined) throw new Error('snapshot-harness: prompt before newSession')
      await client.prompt({ sessionId, prompt: [{ type: 'text', text: step.text }] })
      return
    }
    case 'cancel': {
      const sessionId = getSessionId()
      if (sessionId === undefined) throw new Error('snapshot-harness: cancel before newSession')
      await client.cancel({ sessionId })
      return
    }
    default:
      throw new Error(`snapshot-harness: unknown input op ${JSON.stringify(step)}`)
  }
}

/** Resolve once the child process exits (any code/signal). */
function waitForExit(child: ChildProcessWithoutNullStreams): Promise<void> {
  if (child.exitCode !== null || child.signalCode !== null) return Promise.resolve()
  return new Promise<void>(resolve => child.once('exit', () => { resolve() }))
}

/** Find the single produced `.jsonl` session log under a sessions root, if any. */
async function findSessionLog(root: string): Promise<string | undefined> {
  let cwdDirs: string[]
  try {
    cwdDirs = await readdir(root)
  } catch {
    return undefined
  }
  for (const dir of cwdDirs) {
    const sub = join(root, dir)
    let files: string[]
    try {
      files = await readdir(sub)
    } catch {
      continue
    }
    const jsonl = files.find(f => f.endsWith('.jsonl'))
    if (jsonl !== undefined) return join(sub, jsonl)
  }
  return undefined
}