Ignoring GEM because its extensions are not built

I came across this exact issue today - getting warnings like this for gems that weren't even installed!

... Well, it turns out the gems were installed - for a different ruby than the one I had set active with chruby (2.2.3 vs 2.3.1).

Switching to all the different rubies and running gem pristine --all on all of them solved the problem.

I've had this problem today too and it frustrated because I couldn't type because my whole editor flashed red with error messages.

I'm not entirely sure what exactly caused it but I believe it's because we have multiple ruby versions OR multiple ruby version managers installed and they overwrite each other and otherwise mess up your paths towards the gems.

The gem command also gets overwritten when you have rbenv and rvm.

See which ones you've installed by typing;

which rvm
which rbenv
which chruby

If one of those is installed it'll return a path. Then delete them, make sure to completely clean out all the directories and start with a clean install.

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Remove

Here's what I did for rvm;

rvm implode
gem uninstall rvm
rm -rf ~/.rvm
rm -rf ~/.rvmrc

Here's what I did for rbenv

First installed https://github.com/meowsus/rbenv-clean, then

rbenv clean
sudo apt-get remove rbenv
rm -rf ~/.rbenv

Reinstall

Then you have a clean home directory to work from. I reïnstalled rbenv with How to install Ruby 2.1.4 on Ubuntu 14.04. And finally;

rbenv rehash

I ran into this issue and followed all the same commands as above, even going so far as to remove all my previously installed Ruby versions. However, the error persisted.

Turns out, there were some leftover gems for the various (previously uninstalled) versions in ~/.gem/ruby/. After removing the folders I no longer used, the errors disappeared.