vm: constants is undefined #52716

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1. Jamesernator commented on Apr 27, 2024

   

   Jamesernator

   on Apr 27, 2024

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   It is available if you use default import:

   import vm from "node:vm";

   But it does seem like a bug that it isn't exposed as a named export (maybe because it's experimental?).
2. targos commented on Apr 27, 2024

   

   targos

   on Apr 27, 2024

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   Can't reproduce:

   $ cat test.mjs
   import { constants } from 'node:vm';
   console.log(constants);
   
   $ node test.mjs
   [Object: null prototype] {
     USE_MAIN_CONTEXT_DEFAULT_LOADER: Symbol(vm_dynamic_import_main_context_default)
   }
   
3. avivkeller

   added

   vmIssues and PRs related to the vm subsystem.Issues and PRs related to the vm subsystem.

   on Apr 27, 2024
4. ShafSpecs commented on Apr 27, 2024

   

   ShafSpecs

   on Apr 27, 2024

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   import { constants } from 'node:vm';
   console.log(constants);

   Using your same code:

   $ node test.mjs
   [Object: null prototype] {
     USE_MAIN_CONTEXT_DEFAULT_LOADER: Symbol(vm_dynamic_import_main_context_default)
   }
   # used `require` here
   $ node test.cjs
   [Object: null prototype] {
     USE_MAIN_CONTEXT_DEFAULT_LOADER: Symbol(vm_dynamic_import_main_context_default)
   }

   Both worked. I am now a tadbit confused, when I build my project and compile to bytecode, I am using the vm later on to interpret it. constants in my bytecode loader script is undefined. But it works when I just create a script in my project and node ./test.cjs directly.

   This is some of the bytecode loader code:

   const fs = require("fs");
   const path = require("path");
   const {Script,constants} = require("node:vm");
   const v8 = require("v8");
   const Module = require("module");
   v8.setFlagsFromString("--no-lazy");
   v8.setFlagsFromString("--no-flush-bytecode");
   const FLAG_HASH_OFFSET = 12;
   const SOURCE_HASH_OFFSET = 8;
   let dummyBytecode;
   console.log(constants); // logs 'undefined'
   function setFlagHashHeader(bytecodeBuffer) {
     if (!dummyBytecode) {
       const script = new Script("", {
         produceCachedData: true,
         // trying to actually use it here
       });
       dummyBytecode = script.createCachedData();
     }
     dummyBytecode.slice(FLAG_HASH_OFFSET, FLAG_HASH_OFFSET + 4).copy(bytecodeBuffer, FLAG_HASH_OFFSET);
   };
   // ....
5. joyeecheung commented on May 1, 2024

   

   joyeecheung

   on May 1, 2024

   Last edited by joyeecheung

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   Maybe somehow you are not using the right version of Node.js that has vm.constants to load it?
6. ShafSpecs commented on May 1, 2024

   

   ShafSpecs

   on May 1, 2024

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   Maybe somehow you are not using the right version of Node.js that has vm.constants to load it?

   Running process.versions.node pretty much answered it. I am using version 20 at runtime, but my version is 22. Not sure how to force an upgrade, I tried nvmrc, npmrc, engine strict, and engines config but they didn't do it. Might be a case of my project dependencies bundled with node 20?
7. avivkeller

   closed this as completedon May 4, 2024
8. avivkeller commented on May 4, 2024

   

   avivkeller

   on May 4, 2024

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   Hi, it seems the issue was resolved, but if anyone disagrees, please re open this issue