From 6973036cc676d247ebfa4e645dbe62bb41305766 Mon Sep 17 00:00:00 2001
From: Kris Kowal <kris@agoric.com>
Date: Fri, 19 Jul 2024 16:17:40 -0700
Subject: [PATCH] refactor(xsnap): Remove redundant defer.js

---
 packages/xsnap/src/defer.js  | 31 -------------------------------
 packages/xsnap/src/xsnap.js  | 12 ++++--------
 packages/xsnap/src/xsrepl.js | 12 ++++++------
 3 files changed, 10 insertions(+), 45 deletions(-)
 delete mode 100644 packages/xsnap/src/defer.js

diff --git a/packages/xsnap/src/defer.js b/packages/xsnap/src/defer.js
deleted file mode 100644
index cd3d70f2c63..00000000000
--- a/packages/xsnap/src/defer.js
+++ /dev/null
@@ -1,31 +0,0 @@
-/**
- * @param {boolean} _flag
- * @returns {asserts _flag}
- */
-
-function assert(_flag) {}
-
-/**
- * @template T
- * @typedef {{
- *   resolve(value?: T | Promise<T>): void,
- *   reject(error: Error): void,
- *   promise: Promise<T>
- * }} Deferred
- */
-
-/**
- * @template T
- * @returns {Deferred<T>}
- */
-export function defer() {
-  let resolve;
-  let reject;
-  const promise = new Promise((res, rej) => {
-    resolve = res;
-    reject = rej;
-  });
-  assert(resolve !== undefined);
-  assert(reject !== undefined);
-  return { promise, resolve, reject };
-}
diff --git a/packages/xsnap/src/xsnap.js b/packages/xsnap/src/xsnap.js
index a0fe1baa5b2..a6a87223330 100644
--- a/packages/xsnap/src/xsnap.js
+++ b/packages/xsnap/src/xsnap.js
@@ -10,18 +10,14 @@ import { makeNodeReader, makeNodeWriter } from '@endo/stream-node';
 import { makePromiseKit, racePromises } from '@endo/promise-kit';
 import { forever } from '@agoric/internal';
 import { ErrorCode, ErrorSignal, ErrorMessage, METER_TYPE } from '../api.js';
-import { defer } from './defer.js';
+
+/** @import {PromiseKit} from '@endo/promise-kit' */
 
 /**
  * @typedef {typeof import('child_process').spawn} Spawn
  * @import {Writable} from 'stream'
  */
 
-/**
- * @template T
- * @typedef {import('./defer.js').Deferred<T>} Deferred
- */
-
 // This will need adjustment, but seems to be fine for a start.
 export const DEFAULT_CRANK_METERING_LIMIT = 1e8;
 
@@ -185,8 +181,8 @@ export async function xsnap(options) {
     import.meta.url,
   ).pathname;
 
-  /** @type {Deferred<void>} */
-  const vatExit = defer();
+  /** @type {PromiseKit<void>} */
+  const vatExit = makePromiseKit();
 
   assert(!/^-/.test(name), `name '${name}' cannot start with hyphen`);
 
diff --git a/packages/xsnap/src/xsrepl.js b/packages/xsnap/src/xsrepl.js
index 4581e48713f..3eede346bba 100755
--- a/packages/xsnap/src/xsrepl.js
+++ b/packages/xsnap/src/xsrepl.js
@@ -4,17 +4,15 @@
 
 import '@endo/init';
 
-/**
- * @template T
- * @typedef {import('./defer.js').Deferred<T>} Deferred
- */
 import * as childProcess from 'child_process';
 import fs from 'fs';
 import { tmpName } from 'tmp';
 import * as os from 'os';
 import * as readline from 'readline';
+import { makePromiseKit } from '@endo/promise-kit';
 import { xsnap } from './xsnap.js';
-import { defer } from './defer.js';
+
+/** @import {PromiseKit} from '@endo/promise-kit' */
 
 const decoder = new TextDecoder();
 
@@ -65,7 +63,9 @@ async function main() {
    * @returns {Promise<string>}
    */
   function ask(prompt) {
-    const { promise, resolve } = /** @type {Deferred<string>} */ (defer());
+    const { promise, resolve } = /** @type {PromiseKit<string>} */ (
+      makePromiseKit()
+    );
     rl.question(prompt, resolve);
     return promise;
   }