Speed up CI

[novemberborn]

Inspired by https://twitter.com/kentcdodds/status/786282951210262528 I looked into caching npm and node_modules, which led to some more improvements:

• Stop testing Node.js v5
• In Travis, only install latest npm if the Node.js version is older than v6 (though I suppose when v4 ships we may want to change that again, or actually force it to install v3)
• Cache npm cache and node_modules in both Travis and Appveyor
• Clean up Appveyor config a little

On Travis the first, non-cached run took 5m59s. The second run took 4m15s. I think it saves on nyc instrumentation too since that's cached in node_modules. On Appveyor the time went from 13m3s to 9m30s (note that Appveyor doesn't run builds in parallel for us).

[vadimdemedes]

[jamestalmage]

I definitely wouldn't cache node_modules. If deps are removed from package.json, they won't be cleared. This introduces initial state to the build, meaning CI no longer verifies it will install from scratch.

I am not sure about $HOME/.npm. If caching it does mask any problems, it seems certain those problems will be with npm.

[jamestalmage]

The speedup is drastic enough on Appveyor that it's probably worth it there. I'd avoid it on Travis though.

[vadimdemedes]

Can simplify this:

Number(process.version.match(/^v(\d+)/)[1])

into:

Number(process.version.slice(1)[0])

[novemberborn]

That'll break in 2018 when Node.js v10 ships. I'd rather just do it properly.

[vadimdemedes]

Good catch.

[novemberborn]

I definitely wouldn't cache node_modules. If deps are removed from package.json, they won't be cleared. This introduces initial state to the build, meaning CI no longer verifies it will install from scratch.

npm still verifies all declared dependencies are present though. We could end up deleting a dependency that we still use, yes, but we have a similar problem with deduped dependencies.

Perhaps we could run npm prune after installation?

[sindresorhus]

We could end up deleting a dependency that we still use, yes, but we have a similar problem with deduped dependencies.

The latest XO prevents this through the import/no-unresolved rule.

[novemberborn]

The latest XO prevents this through the import/no-unresolved rule.

That should help. Worth pruning then? Are you OK with caching in Travis given #1080?

[sindresorhus]

I'm still sceptical to caching the node_modules folder, but I'm open to trying it out and see how it works out. As long as we use np when publishing, we're certain we'll at least never publish a broken version. And yes, let's do pruning.

Now pinning npm version, is that OK?