Deploy to Heroku button failing to deploy

[mpoli]

The "Deploy to Heroku" button on the REAME page isn't working.

It seems like the problem lays with stack/buildpack selection in Heroku.

A full log is provided below:

-----> Building on the Heroku-20 stack
-----> Determining which buildpack to use for this app
 !     Warning: Multiple default buildpacks reported the ability to handle this app. The first buildpack in the list below will be used.
			Detected buildpacks: Ruby,Node.js
			See https://devcenter.heroku.com/articles/buildpacks#buildpack-detect-order
-----> Ruby app detected
-----> Installing bundler 2.2.21
-----> Removing BUNDLED WITH version in the Gemfile.lock
-----> Compiling Ruby/Rails
       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-20/ruby-2.6.5.tgz -s -o - | tar zxf - ' failed on attempt 1 of 3.
       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-20/ruby-2.6.5.tgz -s -o - | tar zxf - ' failed on attempt 2 of 3.
 !
 !     The Ruby version you are trying to install does not exist on this stack.
 !     
 !     You are trying to install ruby-2.6.5 on heroku-20.
 !     
 !     Ruby ruby-2.6.5 is present on the following stacks:
 !     
 !     - heroku-18
 !     
 !     Heroku recommends you use the latest supported Ruby version listed here:
 !     https://devcenter.heroku.com/articles/ruby-support#supported-runtimes
 !     
 !     For more information on syntax for declaring a Ruby version see:
 !     https://devcenter.heroku.com/articles/ruby-versions
 !
 !     Push rejected, failed to compile Ruby app.
 !     Push failed

[Matho]

Hi @mpoli

The log says, that you try to use ruby-2.6.5 on heroku-20 stack (which is default now), but that version of Ruby is not supported on heroku-20. It suggest to use the older heroku-18 stack, instead of default heroku-20

You can find the solution on this link https://stackoverflow.com/questions/66279424/you-are-trying-to-install-ruby-2-6-3-on-heroku-20

This command should show you, which stack is default (heroku-20)
$ heroku stack

This will switch your default stack to heroku-18 for all new apps
$ heroku stack:set heroku-18

If you want to use heroku-18 only for one app, this --app switch should work
$ heroku stack:set heroku-18 --app your-app-name

Currently supported Ruby versions for heroku-20 can be seen here:
https://devcenter.heroku.com/articles/ruby-support#supported-runtimes

More info about stacks and stack EOL is available on
https://devcenter.heroku.com/articles/stack

To fix the 'deploy to Heroku' button, the maintainers need to upgrade ruby version to the supported one from the ruby list in heroku-20 stack

Did this instructions fix your problem?