Today some of my colleagues were trying to integrate csslint into the build process of a project using the nodejs package but they kept hitting an issue:

npm ERR! Unsupported
npm ERR! Not compatible with your operating system or architecture: csslint@0.9.7
npm ERR! Valid OS:    darwin,linux
npm ERR! Valid Arch:  any
npm ERR! Actual OS:   win32
npm ERR! Actual Arch: ia32

So I had a crack on my machine and it worked just fine. This was rather confusing until we compared versions. I was running version 0.6.11 where as they were running 0.6.13. This didn’t make sense, why could I install it but they couldn’t?

I put on my detective hat and went hunting, the first thing I found was that there is an OS restriction in the package.json file:

"os": ["darwin", "linux"],

This doesn’t include windows anywhere, but it also doesn’t explain why it worked on my Win7 x64 install but not theirs.

Then I went back and checked out what changed between the two versions of Node.js, in particular what changed with npm.

That’s when I came across the release notes for 0.7.6. While true this is for the 0.7.* unstable branch and we’re using the 0.6.* stable what’s worth noting is the first change for npm version 1.1.8:

Add support for os/cpu fields in package.json (Adam Blackburn)

I then looked at the 0.6.13 release, it’s using npm 1.1.9. Compare that to 0.6.11 which used npm 1.1.1 and I think we’ve found our issue. In the change between the two Node versions we’ve got a new npm version which supports something that wasn’t supported before!

A simple fork and pull request and the problem is solved and now we have to wait for the next version for csslint to be published.

Lesson Learnt

npm now supports the OS (and CPU) package.json property from CommonJS so make sure you check that properly!