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index.js
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index.js
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// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2.0 License.
//
// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2021 Datadog, Inc.
const path = require('path')
const parse = require('module-details-from-path')
const { fileURLToPath } = require('url')
const { MessageChannel } = require('worker_threads')
const {
importHooks,
specifiers,
toHook
} = require('./lib/register')
function addHook (hook) {
importHooks.push(hook)
toHook.forEach(([name, namespace]) => hook(name, namespace))
}
function removeHook (hook) {
const index = importHooks.indexOf(hook)
if (index > -1) {
importHooks.splice(index, 1)
}
}
function callHookFn (hookFn, namespace, name, baseDir) {
const newDefault = hookFn(namespace, name, baseDir)
if (newDefault && newDefault !== namespace) {
namespace.default = newDefault
}
}
let sendModulesToLoader
/**
* EXPERIMENTAL
* This feature is experimental and may change in minor versions.
* **NOTE** This feature is incompatible with the {internals: true} Hook option.
*
* Creates a message channel with a port that can be used to add hooks to the
* list of exclusively included modules.
*
* This can be used to only wrap modules that are Hook'ed, however modules need
* to be hooked before they are imported.
*
* ```ts
* import { register } from 'module'
* import { Hook, createAddHookMessageChannel } from 'import-in-the-middle'
*
* const { registerOptions, waitForAllMessagesAcknowledged } = createAddHookMessageChannel()
*
* register('import-in-the-middle/hook.mjs', import.meta.url, registerOptions)
*
* Hook(['fs'], (exported, name, baseDir) => {
* // Instrument the fs module
* })
*
* // Ensure that the loader has acknowledged all the modules
* // before we allow execution to continue
* await waitForAllMessagesAcknowledged()
* ```
*/
function createAddHookMessageChannel () {
const { port1, port2 } = new MessageChannel()
let pendingAckCount = 0
let resolveFn
sendModulesToLoader = (modules) => {
pendingAckCount++
port1.postMessage(modules)
}
port1.on('message', () => {
pendingAckCount--
if (resolveFn && pendingAckCount <= 0) {
resolveFn()
}
}).unref()
function waitForAllMessagesAcknowledged () {
// This timer is to prevent the process from exiting with code 13:
// 13: Unsettled Top-Level Await.
const timer = setInterval(() => { }, 1000)
const promise = new Promise((resolve) => {
resolveFn = resolve
}).then(() => { clearInterval(timer) })
if (pendingAckCount === 0) {
resolveFn()
}
return promise
}
const addHookMessagePort = port2
const registerOptions = { data: { addHookMessagePort, include: [] }, transferList: [addHookMessagePort] }
return { registerOptions, addHookMessagePort, waitForAllMessagesAcknowledged }
}
function Hook (modules, options, hookFn) {
if ((this instanceof Hook) === false) return new Hook(modules, options, hookFn)
if (typeof modules === 'function') {
hookFn = modules
modules = null
options = null
} else if (typeof options === 'function') {
hookFn = options
options = null
}
const internals = options ? options.internals === true : false
if (sendModulesToLoader && Array.isArray(modules)) {
sendModulesToLoader(modules)
}
this._iitmHook = (name, namespace) => {
const filename = name
const isBuiltin = name.startsWith('node:')
let baseDir
if (isBuiltin) {
name = name.replace(/^node:/, '')
} else {
if (name.startsWith('file://')) {
try {
name = fileURLToPath(name)
} catch (e) {}
}
const details = parse(name)
if (details) {
name = details.name
baseDir = details.basedir
}
}
if (modules) {
for (const moduleName of modules) {
if (moduleName === name) {
if (baseDir) {
if (internals) {
name = name + path.sep + path.relative(baseDir, fileURLToPath(filename))
} else {
if (!baseDir.endsWith(specifiers.get(filename))) continue
}
}
callHookFn(hookFn, namespace, name, baseDir)
}
}
} else {
callHookFn(hookFn, namespace, name, baseDir)
}
}
addHook(this._iitmHook)
}
Hook.prototype.unhook = function () {
removeHook(this._iitmHook)
}
module.exports = Hook
module.exports.Hook = Hook
module.exports.addHook = addHook
module.exports.removeHook = removeHook
module.exports.createAddHookMessageChannel = createAddHookMessageChannel