在 Heroku 上降级/恢复 Ruby 版本

Question

I recently updated my Heroku app from Ruby 2.3.1 to 2.4.0 , but I now need to revert back to version 2.3.1 .

To Update:

I changed the version in the Gemfile from 2.3.1 to 2.4.0 . Everything went fine, but I need to go back to 2.3.1 because of problems specific to me with 2.4.0

To Revert:

I've tried changing the version back to 2.3.1 in my Gemfile (as ruby "2.3.1" ) but it just throws the bundler error Your Ruby version is 2.4.0, but your Gemfile specified 2.3.1

How do I change my Ruby version back to 2.3.1 on Heroku?

Here is the error on deployment:

ID yupp
-----> heroku-buildpack-rgeo-prep app detected
-----> Removing cached .bundle/config
       Writing new .bundle/config
-----> VendorBinaries app detected
-----> Found a .vendor_urls file
-----> Ruby app detected
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-2.4.0
###### WARNING:
       You have the `.bundle/config` file checked into your repository
       It contains local state like the location of the installed bundle
       as well as configured git local gems, and other settings that should
       not be shared between multiple checkouts of a single repo. Please
       remove the `.bundle/` folder from your repo and add it to your `.gitignore` file.
       https://devcenter.heroku.com/articles/bundler-configuration
-----> Installing dependencies using bundler 1.13.7
       Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
       Warning: the running version of Bundler (1.13.7) is older than the version that created the lockfile (1.14.3). We suggest you upgrade to the latest version of Bundler by running `gem install bundler`.
       Your Ruby version is 2.4.0, but your Gemfile specified 2.3.1
       Bundler Output: Warning: the running version of Bundler (1.13.7) is older than the version that created the lockfile (1.14.3). We suggest you upgrade to the latest version of Bundler by running `gem install bundler`.
       Your Ruby version is 2.4.0, but your Gemfile specified 2.3.1
 !
 !     Failed to install gems via Bundler.
 !     Detected a mismatch between your Ruby version installed and
 !     Ruby version specified in Gemfile or Gemfile.lock:
 !     https://devcenter.heroku.com/articles/ruby-versions#your-ruby-version-is-x-but-your-gemfile-specified-y
 !
 !     Push rejected, failed to compile Ruby app.
 !     Push failed

Answer 1

I figured it out. Here are the steps

Locally:

Change the Ruby version from 2.4.0 to 2.3.1

Verify the version is 2.3.1 with ruby -v

Run gem install bundler && gem install rails

Run bundle install

Commit the Gemfile and Gemfile.lock and push to Heroku