Make client more ESM-friendly (#2348)

* Use node: prefix for stdlib imports

* Make code more ESM-friendly

* Add missing mjs file

* Drop mjs file from package.json

src/client.ts

@@ -17,10 +17,11 @@
  * under the License.
  */
 
-import { ConnectionOptions as TlsConnectionOptions } from 'tls'
-import { URL } from 'url'
-import buffer from 'buffer'
-import os from 'os'
+import process from 'node:process'
+import { ConnectionOptions as TlsConnectionOptions } from 'node:tls'
+import { URL } from 'node:url'
+import buffer from 'node:buffer'
+import os from 'node:os'
 import {
   Transport,
   UndiciConnection,
@@ -48,16 +49,18 @@ import BaseConnection, { prepareHeaders, ConnectionOptions } from '@elastic/tran
 import SniffingTransport from './sniffingTransport'
 import Helpers from './helpers'
 import API from './api'
+import packageJson from '../package.json'
+import transportPackageJson from '@elastic/transport/package.json'
 
 const kChild = Symbol('elasticsearchjs-child')
 const kInitialOptions = Symbol('elasticsearchjs-initial-options')
-let clientVersion: string = require('../package.json').version // eslint-disable-line
+let clientVersion: string = packageJson.version
 /* istanbul ignore next */
 if (clientVersion.includes('-')) {
   // clean prerelease
   clientVersion = clientVersion.slice(0, clientVersion.indexOf('-')) + 'p'
 }
-let transportVersion: string = require('@elastic/transport/package.json').version // eslint-disable-line
+let transportVersion: string = transportPackageJson.version // eslint-disable-line
 /* istanbul ignore next */
 if (transportVersion.includes('-')) {
   // clean prerelease

src/helpers.ts

@@ -21,9 +21,9 @@
 /* eslint-disable @typescript-eslint/promise-function-async */
 /* eslint-disable @typescript-eslint/no-unnecessary-type-assertion */
 
-import assert from 'assert'
-import { promisify } from 'util'
-import { Readable } from 'stream'
+import assert from 'node:assert'
+import * as timersPromises from 'node:timers/promises'
+import { Readable } from 'node:stream'
 import { errors, TransportResult, TransportRequestOptions, TransportRequestOptionsWithMeta } from '@elastic/transport'
 import Client from './client'
 import * as T from './api/types'
@@ -163,8 +163,8 @@ export interface EsqlToRecords<TDocument> {
 }
 
 const { ResponseError, ConfigurationError } = errors
-const sleep = promisify(setTimeout)
-const pImmediate = promisify(setImmediate)
+const sleep = timersPromises.setTimeout
+const pImmediate = timersPromises.setImmediate
 /* istanbul ignore next */
 const noop = (): void => {}
 const kClient = Symbol('elasticsearch-client')

src/sniffingTransport.ts

@@ -17,7 +17,7 @@
  * under the License.
  */
 
-import assert from 'assert'
+import assert from 'node:assert'
 import { Transport, SniffOptions } from '@elastic/transport'
 
 export default class SniffingTransport extends Transport {