It would happen when the gem is already installed to multiple GEM_PATHS.
RubyGems was removing duplicate specs without considering the
potentially different `base_dir`. That was causing the gem to be
misidentified as not already installed, and a nil specification getting
returned from the installer as a result, causing the crash.
Solve it by making sure `Gem::Specification.all` really iterates through
all the different specifications in all GEM_PATHs.
0d8c208f65
When `gem uninstall <gem> --install-dir <dir>` is run, if the version
removed had a plugin, and that same version happened to also be
installed globally, then the plugin stub would fail to be removed.
4e2fa0be77
This class handles all logic to handle the list of specifications, given
a set of GEM_PATH directories. Makes `Gem::Specification` has less
responsibilities and will help with fixing some bugs next.
df280dbbed
