Cannot find package 'mem-fs' imported from

[chk4658]

Type of issue

npm install -g yo generator-code

and yo code failed

C:\Users\KHC1SZH\chenkai\Projects\vscodePluginsDemo>yo code
Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'mem-fs' imported from C:\Users\KHC1SZH\chenkai\node-v14.17.2-win-x64\node_global\node_modules\yo\node_modules\yeoman-environment\dist\environment-base.js
    at packageResolve (internal/modules/esm/resolve.js:650:9)
    at moduleResolve (internal/modules/esm/resolve.js:691:18)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:805:11)
    at Loader.resolve (internal/modules/esm/loader.js:88:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:241:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:72:40)
    at link (internal/modules/esm/module_job.js:71:36)

---

My environment

• OS version/details: eg. Windows 10 64-bit
• Node version: v14.17.2 (run node --version in your terminal)
• npm version: 6.14.13 (run npm --version in your terminal)
• Version of yo : 5.0.0 (run yo --version in your terminal)

Expected behavior

Need an upgrade for node? or downgrade yo. What should I do?

Current behavior

C:\Users\KHC1SZH\chenkai\Projects\vscodePluginsDemo>npm install -g mem-fs
npm WARN notsup Unsupported engine for [email protected]: wanted: {"node":">=18.0.0"} (current: {"node":"14.17.2","npm":"6.14.13"})
npm WARN notsup Not compatible with your version of node/npm: [email protected]

+ [email protected]
added 19 packages from 81 contributors in 1.872s

C:\Users\KHC1SZH\chenkai\Projects\vscodePluginsDemo>yo code
Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'stream' imported from C:\Users\KHC1SZH\chenkai\node-v14.17.2-win-x64\node_global\node_modules\mem-fs\dist\index.js
    at packageResolve (internal/modules/esm/resolve.js:650:9)
    at moduleResolve (internal/modules/esm/resolve.js:691:18)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:805:11)
    at Loader.resolve (internal/modules/esm/loader.js:88:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:241:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:72:40)
    at link (internal/modules/esm/module_job.js:71:36)

Steps to reproduce the behavior

Command line output

Paste your error output over here

[1071125093]

same

[1071125093]

stiff but fixed
1.need nvm, install node 20.5.0
2.reinstall yo generator-code

[filipboca]

Same for me, still does not work on 20.5

[atulbhatt-system32]

I am also facing the same issue

[mshima]

C:\Users\KHC1SZH\chenkai\Projects\vscodePluginsDemo>node --version v14.17.2

C:\Users\KHC1SZH\chenkai\Projects\vscodePluginsDemo>npm --version 6.14.13

yo@5 requires node 18 and npm should be at least v7, latest is recommended.

[atulbhatt-system32]

I tried with node -v (21.5.0) and npm -v (10.2.4) but what worked for me was downgrading yo to version 4.3.1

[atulbhatt-system32]

@mshima is node 18 the minimum requirement or greater also works for yo@5 as in my case it didn't.
node -v (21.5.0) and npm -v (10.2.4)

[mshima]

yo must be installed with newer npm (must support peer dependencies).

npm install -g npm@latest
npm uninstall -g yo generator-code
npm install -g yo generator-code
npm uninstall yo generator-code # make sure it’s not installed locally
yo code

[isMattCoding]

Playing with the npm and node versions didn't work for me.

It seems that this issue still persists, but what allowed me to continue was running:

npm install -g yo generator-code mem-fs
yo code

[erikJonsberg]

Playing with the npm and node versions didn't work for me.

It seems that this issue still persists, but what allowed me to continue was running:

npm install -g yo generator-code mem-fs
yo code

This worked for me as well. However, I need to reinstall mem-fs globally each time I run yo code. Does anyone know why? It should already be installed, right?

[schroeder-g]

Playing with the npm and node versions didn't work for me.
It seems that this issue still persists, but what allowed me to continue was running:

npm install -g yo generator-code mem-fs
yo code

This worked for me as well. However, I need to reinstall mem-fs globally each time I run yo code. Does anyone know why? It should already be installed, right?

The above alone didn't resolve the issue for me. The fix that I found was to:

0. Uninstall all the relevant packages, nvm use v20.14.0, npm install -g yo generator-code mem-fs
1. navigate to the install location for yeoman indicated in the error: code /path/to/node_modules/yeoman-generator
2. npm install mem-fs
3. npm run build to recompile dist with tsc.
4. yo > choose generator.

Hilariously, there's no tsconfig.json in the project, so the build step resulted in me transpiling all TypeScript files in my home directory. Would recommend just copying theirs into the project root to avoid this issue.

[wesleyscholl]

npm install -g yo generator-code mem-fs

This worked for me, thanks!

[JoshuaKGoldberg]

This doesn't reproduce for me.

• OS: macOS Ventura 13.2
• Node.js: 20, 22, and 23

But, I think it's really an issue with generators and not with yo itself. I think the root of this issue is as follows:

• The mem-fs project is not a production dependency (dependencies) of yeoman-generator, just a peer dependency (peerDependencies)
  • This is good and expected because it allows generators to define their expected mem-fs dependency range themselves
• Some generators don't explicitly declare a production dependency on mem-fs, instead assuming it to be coincidentally available in node_modules/
• That assumption used to be reliable, but in more recent versions of package edit: npm, is not - resulting in Cannot find package 'mem-fs'

If I'm right, the correct resolution for this issue is to get generators such as https://github.com/microsoft/vscode-generator-code to explicitly declare their dependency on mem-fs. I.e. running npm i mem-fs (or equivalent).

Tagging in @UlisesGascon for another set of eyes, does that seem right to you?

See also: yeoman/generator#1493, yeoman/generator#1502.

[UlisesGascon]

the correct resolution for this issue is to get generators such as microsoft/vscode-generator-code to explicitly declare their dependency on mem-fs.

+1 I think is the best solution

[eddiemonge]

but in more recent versions of package, is not

Its actually in more recent versions of npm. Back when this was written, npm would install peerDependencies where it found them. Then the behavior changed to not install peerDeps. This caused a lot of frustration and npm has gone back and forth on the issue.

A better approach might be to list mem-fs as a dependency with >= range, or a ^ range of major versions supported.

Also, this issue should probably be moved to https://github.com/yeoman/environment as that is where it is defined, not here. Its also odd thats it both a dep and a peerDep there

[JoshuaKGoldberg]

Also, this issue should probably be moved to https://github.com/yeoman/environment as that is where it is defined, not here. Its also odd thats it both a dep and a peerDep there

🤔 sorry, I'm a bit lost - yeoman-environment already lists mem-fs as a dep and a peerDep. +1 that it's confusing to have both, but separately from that - why would this issue be native to that package/repository?

[IOLOII]

You need fix global installed mem-fs

yarn global add mem-fs
npm install mem-fs --global

# may need , if you are pnpm
pnpm install mem-fs --global

For reason detail you can see this 👉 [#803 ](#803 (comment))

[JoshuaKGoldberg]

@IOLOII I don't think that's the right long-term solution. It might fix things for now but it doesn't resolve the root issue. That is, packages shouldn't need to rely on global installations for dependencies like mem-fs. Their dependencies should be properly declared in their package.jsons.

In fact, I would recommend folks don't install mem-fs globally at first. If something is broken then we'd want to know about it here! We're still waiting on a reproduction so we can figure out how to fix this issue: #800 (comment).