init

.gitignore

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+node_modules

LICENSE.txt

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+Copyright (c) 2023 Bryan English
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# is-really-node
+
+Sometimes you want to make sure that the JavaScript runtime you're expecting to
+be running on is the one you're actually running on. With this library, you can
+detect whether you're actually running inside Node.js, and not Deno or Bun. A
+single (default) export is provided, and it's a boolean that's true if we're
+definitely running inside Node.js.
+
+This is done by first checking verious globals, and then attempting to alter v8
+options, and testing those options have been altered. This is only currently
+possible in Node.js. The aim is to never have false negatives, and also load
+quickly if the globals-checking gives us a negative.
+
+## Some Details (FAQ)
+
+* Why not TypeScript or at least JSDoc?
+  * The module is very small, and the code does some things that would probably
+  piss off `tsc`.
+  * I don't use TypeScript in my day job, so I tend not to default to it. Don't
+  worry, I'm not one of those haters you see on Twitter.
+  * Submit a PR that works correctly and I'll add it.
+* Okay, but why no `.d.ts`?
+  * I'm lazy and Keep forgetting how to do that for default exports, since I
+  don't use TypeScript in my day job. Submit a PR and I'll add it.
+* Do you just hate Bun and Deno? Are you some Node.js purist? They're both 
+  Node.js compatible anyway!
+  * No. A lot of code I work with targets very specific runtime things that
+    only work in Node.js, so I want an easy way to bail early if that stuff
+    isn't going to work, even if the runtime is trying to fake that it's
+    Node.js. That's all. Please feel free to create `is-really-bun` or
+    `is-really-deno` if that suits your work.
+* Isn't checking the globals alone enough?
+  * Nope. If folks are trying to fake that they're in Node.js, they can always
+    mess with the globals. Instead we need to do something that's _truly_
+    impossible in the other platforms, like messing with v8 options.
+* Why no CommonJS?
+  * Deno doesn't support CommonJS, AFAIK.
+  * That's a bad excuse though. Really I should make this work with `require`
+    on  platforms that support it. Submit a PR that handles this and I'll add
+    it.
+
+## License
+
+The MIT License. See LICENSE.txt

index.js

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+/**
+  * First of all, this is a CommonJS module. These aren't supported by Deno,
+  * but that can be worked around with various bundling techniques, etc.
+  */
+
+/**
+  * Let's check for some basic globals. If these aren't present, game over.
+  */
+function hasNodeGlobals() {
+  return typeof global === 'object' &&
+    typeof globalThis === 'object' &&
+    global === globalThis &&
+    global.global === global &&
+    globalThis.globalThis === globalThis &&
+    typeof process === 'object'
+}
+
+/**
+  * Now, we check for the Bun global object. The Bun object is 
+  * non-configurable, so it would be very hard to get past this if trying to 
+  * pretend to be Node.js.
+  */
+function hasBunGlobal() {
+  return typeof Bun !== 'undefined' ||
+    typeof global.Bun !== 'undefined'
+}
+
+/**
+  * We'll do the same here for Deno. The Deno object _can_ be delted, so this
+  * could be faked around, so we need the subsequent test as well.
+  */
+function hasDenoGlobal() {
+  return typeof Deno === 'object' ||
+    typeof global.Deno === 'object'
+}
+
+/**
+  * V8 has "natives syntax" which allows us to do some sneaky things. We'll now
+  * test that those sneaky things are there and working. If it works, then
+  * we're definitely not in Bun, which uses JSC. If it does, we'll try to
+  * disable it, ruling out Deno.
+  */
+async function isNodeIshV8() {
+  let v8
+  try {
+    v8 = await import('node:v8')
+  } catch {
+    return false
+  }
+
+  function privateSymbol() {
+    try {
+      const sym = eval('%CreatePrivateSymbol("testing")')
+      const obj = {}
+      obj[sym] = 3
+      return !Reflect.ownKeys(obj).includes(sym) && obj[sym] === 3
+    } catch {
+      return false
+    }
+  }
+
+  // JSC/Bun doesn't support V8's native syntax.
+  if (privateSymbol()) {
+    // Natives syntax was on. Try turning it off. That' won't work in Deno.
+    v8.setFlagsFromString('--no-allow-natives-syntax')
+    return !privateSymbol()
+  }
+
+  // Deno "supports" this, but it does nothing. So if it failed before, it
+  // will fail again.
+  v8.setFlagsFromString('--allow-natives-syntax')
+  return privateSymbol()
+}
+
+export default hasNodeGlobals() &&
+  !hasBunGlobal() &&
+  !hasDenoGlobal() &&
+  await isNodeIshV8()

package.json

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+{
+  "name": "is-really-node",
+  "version": "1.0.0",
+  "description": "Determine whether the current runtime is _really_ Node.js, or some impostor.",
+  "main": "index.js",
+  "scripts": {
+    "test": "node test"
+  },
+  "type": "module",
+  "repository": {
+    "type": "git",
+    "url": "git+ssh://[email protected]/bengl/is-really-node.git"
+  },
+  "keywords": [
+    "Node.js",
+    "Bun",
+    "Deno",
+    "detect",
+    "environment"
+  ],
+  "author": "Bryan English <[email protected]>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/bengl/is-really-node/issues"
+  },
+  "homepage": "https://github.com/bengl/is-really-node#readme"
+}

test.js

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+import { exec } from 'child_process'
+import test from 'node:test'
+import assert from 'assert'
+
+function run(...args) {
+  return new Promise((resolve, reject) => {
+    exec(...args, (err, stdout, stderr) => {
+      if (err) reject(err)
+      resolve({ stdout, stderr })
+    })
+  })
+}
+
+test('Node.js', async () => {
+  await run('node test/node-test.js')
+})
+
+test('Node.js (allow-natives-syntax)', async () => {
+  await run('node --allow-natives-syntax test/node-test.js')
+})
+
+test('Node.js (no-allow-natives-syntax)', async () => {
+  await run('node --no-allow-natives-syntax test/node-test.js')
+})
+
+test('Deno', async () => {
+  await assert.rejects(
+    () => run('deno run test/node-test.js')
+  )
+})
+
+test('Deno (faking Node.js)', async () => {
+  await assert.rejects(
+    () => run('deno run test/deno-test.js')
+  )
+})
+
+test('Deno (faking Node.js) (allow-natives-syntax)', async () => {
+  await assert.rejects(
+    () => run('deno run --v8-flags="--allow-natives-syntax" test/deno-test.js')
+  )
+})
+
+test('Deno (faking Node.js) (no-allow-natives-syntax)', async () => {
+  await assert.rejects(
+    () => run('deno run --v8-flags="--allow-natives-syntax" test/deno-test.js')
+  )
+})
+
+test('Bun', async () => {
+  await assert.rejects(
+    () => run('deno run test/node-test.js')
+  )
+})
+
+test('Bun (faking Node.js)', async () => {
+  await assert.rejects(
+    () => run('deno run test/deno-test.js')
+  )
+})
+

test/bun-test.js

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+globalThis.global = globalThis
+
+//// Not possible in Bun
+// delete globalThis.Bun
+
+import('./node-test.js')

test/deno-test.js

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+globalThis.global = globalThis
+
+globalThis.process = {}
+
+delete globalThis.Deno
+
+import('./node-test.js')

test/node-test.js

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+import isNode from '../index.js'
+import assert from 'node:assert'
+
+assert.strictEqual(true, isNode)