Yarn silently fails to install package, missing from node_modules

Do you want to request a feature or report a bug?

Bug

What is the current behavior?

Installing dependencies for https://github.com/ipfs/js-ipfs fails silently as karma-mocha-webworker never ends up in node_modules/ directory. Running yarn add karma-mocha-webworker or even npm install installs the package correctly.

If the current behavior is a bug, please provide the steps to reproduce.

• Clone https://github.com/ipfs/js-ipfs.git
• Run yarn
• Now karma-mocha-webworker should be in node_modules/
• Instead, ls node_modules | grep -i webworker ; echo $? returns 1 instead of 0

What is the expected behavior?

Yarn installs all dependencies.

Please mention your node.js, yarn and operating system version.

$ node --version
v9.5.0

$ yarn --version
1.4.1-20180217.1901

$ uname -a
Linux lasoa 4.15.3-1-ARCH #1 SMP PREEMPT Mon Feb 12 23:01:17 UTC 2018 x86_64 GNU/Linux

Extra information

yarn check doesn't find that the module is missing but just mentions it could be deduped.

$ yarn check 2>&1 >/dev/null | grep -i webworker
warning "aegir#karma-mocha-webworker#mocha@*" could be deduped from "5.0.1" to "mocha@5.0.1"

Tried installing modules with both --check-files and --force to no avail.

I've also tried the different versions of yarn, stable and daily. Also the npm version and the standalone.