Pushing to Heroku fails due to unsupported Ruby version even after Gemfile was changed

Question

I'm trying to push a forked repo to Heroku but Heroku won't accept the push because Ruby 2.3.1 wasn't accepted. I changed the version to 2.3.3 in the Gemfile and running bundle install --without production , but oddly enough it was still considered to be 2.3.1. The same things happened even after trying other Ruby versions, such as 2.4.0.

Reference:

$ cat Gemfile.lock | grep -A 2 RUBY
RUBY VERSION
ruby 2.3.3p222
$ bundle platform --ruby
ruby 2.3.3p222

Error:

remote: Building source:
remote:
remote: -----> Ruby app detected
remote: -----> Compiling Ruby/Rails
remote:        Command: 'set -o pipefail; curl -L --fail --retry 5 --retry-delay 1 --connect-timeout 3 --max-time 30 https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/heroku-18/ruby-2.3.1.tgz -s -o - | tar zxf - ' failed on attempt 1 of 3.
remote:        Command: 'set -o pipefail; curl -L --fail --retry 5 --retry-delay 1 --connect-timeout 3 --max-time 30 https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/heroku-18/ruby-2.3.1.tgz -s -o - | tar zxf - ' failed on attempt 2 of 3.
remote:
remote:  !
remote:  !     An error occurred while installing ruby-2.3.1
remote:  !
remote:  !     This version of Ruby is not available on Heroku-18. The minimum supported version
remote:  !     of Ruby on the Heroku-18 stack can found at:
remote:  !
remote:  !     https://devcenter.heroku.com/articles/ruby-support#supported-runtimes
remote:  !
remote:  !     Push rejected, failed to compile Ruby app.
remote:
remote:  !     Push failed

Gemfile:

# -*- mode: ruby; -*-
source 'https://rubygems.org'
ruby '2.3.3'

# basic app components
gem 'pg', '~> 0.21'
gem 'apartment', '>= 2.1.0'     # multi-tenancy: see README.md
gem 'rails', '4.2.9'
gem 'rack-timeout'              # prevent Heroku dynos from hanging up on timeout

gem 'where-or'                  # backport from Rails 5; remove when upgrading

gem 'builder'
gem 'bundler'
gem 'figaro'
gem 'sslrequirement'
gem 'haml'
gem 'gibbon'
gem 'i18n'
gem 'jbuilder', '~> 2.0'
gem 'jquery-rails', '= 4.0.5'
gem 'jquery-ui-rails', '= 5.0.5'
gem 'nokogiri'
gem 'pothoven-attachment_fu'
gem 'protected_attributes'      # remove once we migrate to Strong Parameters
gem 'responders', '~> 2.0'
gem 'attr_encrypted'            # attr_encrypted must load AFTER protected_attributes (https://github.com/attr-encrypted/attr_encrypted/issues/107)
gem 'rake'
gem 'stripe'
gem 'will_paginate'

# asset pipeline
gem 'sprockets-rails', :require => 'sprockets/railtie'
gem 'uglifier'
gem 'sassc-rails'

group :production do
  gem 'newrelic_rpm'
  gem 'puma-heroku'
  gem 'puma'
  gem 'rails_12factor'
end

group :test do
  gem 'cucumber', '~> 2.0'
  gem 'cucumber-rails', '1.5.0', :require => false
  gem 'capybara'
  gem 'fake_stripe'
  gem 'poltergeist'
  gem 'rspec-its'
  gem 'rspec-html-matchers'
  gem 'simplecov', :require => false
  gem 'spring'                  # for 'guard'
  gem 'webmock'
  gem 'vcr'
end

group :development do
  gem 'derailed_benchmarks'
  # gem 'query_trail'
  gem 'ruby-prof'
  gem 'stackprof'
  gem 'web-console', '~> 2.0'
  gem 'spring-commands-rspec'   # for use with Guard
end

group :development, :test do
  # the following really belong in a separate 'staging' environment
  gem 'faker', :git => 'https://github.com/armandofox/faker' # needed in production too,for adding fake data to staging server
  gem 'factory_bot_rails'                                    # used by fake_data stuff

  gem 'bullet'
  # cucumber and capybara
  gem 'yaml_db', :git => 'https://github.com/armandofox/yaml_db'
  gem 'byebug'                  # 4
  gem 'pry'
  gem 'listen', '~> 2.2'
  gem 'guard-rspec', :require => false
  gem 'guard-cucumber'
  gem 'minitest'
  gem 'faye-websocket'
  gem 'database_cleaner'
  gem 'rb-readline'
  gem 'rubyzip'
  gem 'mime-types'
  gem 'chronic'
  gem 'fakeweb'
  gem 'launchy'
  gem 'rack-test'
  gem 'sdoc', '~> 0.4.0'
  gem 'coveralls', :require => false
  gem 'rspec-rails'
  gem 'rspec-collection_matchers' # should have(n).items, etc
  gem 'rspec-activemodel-mocks'   # mock_model(Customer), etc
  gem 'sqlite3'
  gem 'timecop'
  gem 'traceroute'
end

Answer 1

Heroku doesn't support Ruby 2.3.1, 2.3.3 or 2.4.0

Look at your log:

remote:  !     An error occurred while installing ruby-2.3.1
remote:  !
remote:  !     This version of Ruby is not available on Heroku-18. The minimum supported version
remote:  !     of Ruby on the Heroku-18 stack can found at:
remote:  !
remote:  !     https://devcenter.heroku.com/articles/ruby-support#supported-runtimes

Look at the link from your log :

Heroku supports the following Ruby versions and the associated Rubygems. A supported version means that you can expect our tools and platform to work with a given version. It also means you can receive technical support. Here are our supported Ruby versions:

MRI:

• 2.4.5 : patchlevel 335, Rubygems: 2.6.14.4
• 2.5.5: patchlevel 157, Rubygems: 2.7.6.2
• 2.6.2: patchlevel 33, Rubygems: 3.0.3

Also read information how to specify Ruby version .

Pay special attention to the Troubleshooting section. Looks like you didn't commit your Gemfile and Gemfile.lock after changing Ruby version and before pushing to Heroku.