Installing NPM packages with child_process

[Paultje52]

• Node.js Version: 12.17.0
• OS: Windows 10
• Scope (install, code, runtime, meta, other?): Code
• Module (and version) (if relevant): Child_Process

I made a function to ensure that NPM packages are installed. If a package isn't installed, I use child_process to install it.

const childProcess = require("child_process");
function ensureDependencies(dependencies) {
  return new Promise((res) => {
    try {
      for (let i of dependencies) {
        require(i);
      }
      res();
    } catch(e) {
      childProcess.exec(`npm i -s ${dependencies.join(" ")}`, async () => {
        res();
      });
     }
  });
}
ensureDependencies(["discord.js", "express"]).then(() => {
  const discord = require("discord.js");
  const express = require("express");
});

When the packages are already installed, it just continues. When they aren't installed, child_process installs them, without any errors. But when I try to require them, I get a module not found error. When I stop my process and start it again, the packages are installed.

Is there any way to "refresh" the node_modules or whatever? I don't want to restart the process after child_process installed the dependencies.

I also tried deleting the cache, like this, after the child_process exec is compleat.

for (let i of dependencies) {
  delete require.cache[require.resolve(i)];
}

That also doesn't work.

[Paultje52]

It's been almost two weeks. Is this a bug or am I doing something wrong?

[qballer]

Can you please share the error with something like this?

 childProcess.exec(`npm i -s ${dependencies.join(" ")}`, async (error) => {
        if(error) {
          console.log('error is:' , error);
           //or
           throw error;
        }
      res();
});

I believe it would help the community to understand the source of your issue.

Another question: Have you considered using a package json file instead of joining all the dependencies in the command line? You might be hitting the limit of the command line arguments.

[Paultje52]

Hello. I don't get any errors, and the packages install just fine, but node can't find it until I stop and then start the process.

And yes, I thought of putting the packages in the package.json, but it's for a package that maybe require dependencies, bases on which parts you use. That's why I want to install the packages with child_process.

[qballer]

Ok, I've reconstructed the issue. It seems funny because I've dealt with module reloading in the past, but the module was never loaded so I believe this brings us to some kind of edge case.

const childp = require('child_process')
const {resolve} = require('path')
const package = 'rimraf'

try {
  const found = require(package)
  console.log('found', found)
} catch (e) {
  childp.execSync(`npm i ${package}`)
  console.log('installed')
}

console.log('require.cache:', require.cache[package]) // undefined
console.log(require.resolve(package, {paths: [resolve(__dirname, 'node_modules')]})) //💥  shoule be regular require goes 💥

Edit: For those looking to help here when running the script do something along the lines of rm -rf node_modules; node [script_name]

[richardlau]

You're trying to do the same as https://github.com/nodejs/node/issues/31803, which AFAIK is not currently possible due to the internal caching.

[Paultje52]

The strange thing is that it works sometimes, but other times it doesn't work. Is there a way to clear the internal caching or something like that?

[SevenOutman]

It doesn't seem to be about the cache. npm install spawned in child process appeared not to actually install any packages into node_modules, nor updating package.json

[jeasonstudio]

We encountered the same situation, the following example can reproduce the problem.

const { execSync } = require('child_process');

function resolveSilent(id) {
  try {
    return require.resolve(id);
  } catch (e) {
    return undefined;
  }
}

const pkgName = 'add';

const resolveBefore = resolveSilent(pkgName);
console.log('Resolve before: ', resolveBefore);

if (!resolveBefore) {
  const stdout = execSync(`npm i -D ${pkgName}`, { encoding: 'utf8' });
  console.log('stdout: ', stdout);
  console.log('Resolve after: ', resolveSilent(pkgName));
}

[fernandopasik]

I tried the same but with dynamic imports and arrived to the same problem. Has anybody found a way to deal with the cache before attempting the 2nd import/require?

[github-actions[bot]]

It seems there has been no activity on this issue for a while, and it is being closed in 30 days. If you believe this issue should remain open, please leave a comment. If you need further assistance or have questions, you can also search for similar issues on Stack Overflow. Make sure to look at the README file for the most updated links.

[github-actions[bot]]

It seems there has been no activity on this issue for a while, and it is being closed. If you believe this issue should remain open, please leave a comment. If you need further assistance or have questions, you can also search for similar issues on Stack Overflow. Make sure to look at the README file for the most updated links.