From time to time I have this warning
Warning: the running version of Bundler (2.1.2) is older than the version that created the lockfile (2.1.4). We suggest you to upgrade to the version that created the lockfile by running `gem install bundler:2.1.4
Now I can inspect
gem list bundler
The result show bundler 2.1.2 is the default. The default is the one that will be used.
Even you try to install bundler 2.1.4
gem install bunder:2.1.4 # or even with the --default
As default gems are not allowed to be uninstalled, I found this ruby code from https://github.com/rubygems/bundler/issues/7107#issuecomment-572296292
The code returns the directory where default gems reside. You can find the gemspec file and delete it manually.
I found that after deleting the bundler-2.1.2.gemspec from the directory, bundle command still complaint with the warning above then I try this
gem install bundler:2.1.2 # reinstall but not as a default one
Then bundler command maps the version correctly and eventually the warnings’ gone.