Remove support for Heroku-18 (#1449)

Since the Heroku-18 stack has reached end-of-life, and as such build using it
are no longer supported by the Heroku build system:
https://devcenter.heroku.com/changelog-items/2583

This fixes the integration tests failing in CI for the Heroku-18 stack, due to the
build system now (as expected) rejecting the jobs, eg:
https://github.com/heroku/heroku-buildpack-python/actions/runs/4852163562/jobs/8646809603?pr=1448#step:5:165

The Heroku-18 stack was the last to have Python binaries available for Python 2.7,
3.5 and 3.5, so the EOL conditionals and testcases for those versions have now been
removed.

Any non-Heroku consumers of this buildpack that wish to continue using
the Heroku-18 stack should pin to the previous version of this buildpack.

GUS-W-10446293.

.github/workflows/build_python_runtime.yml

@@ -26,21 +26,6 @@ env:
 # Unfortunately these jobs cannot be easily written as a matrix since `matrix.exclude` does not
 # support expression syntax, and the `inputs` context is not available inside the job `if` key.
 jobs:
-  build-and-upload-heroku-18:
-    runs-on: pub-hk-ubuntu-22.04-xlarge
-    env:
-      STACK_VERSION: "18"
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-      - name: Build Docker image
-        run: docker build --pull --tag buildenv --build-arg=STACK_VERSION builds/
-      - name: Build and package Python runtime
-        run: docker run --rm --platform="linux/amd64" --volume="${PWD}/upload:/tmp/upload" buildenv ./build_python_runtime.sh "${{ inputs.python_version }}"
-      - name: Upload Python runtime archive to S3
-        if: (!inputs.dry_run)
-        run: aws s3 sync ./upload "s3://${S3_BUCKET}"
-
   build-and-upload-heroku-20:
     runs-on: pub-hk-ubuntu-22.04-xlarge
     env:

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        stack: ["heroku-18", "heroku-20", "heroku-22"]
+        stack: ["heroku-20", "heroku-22"]
     env:
       HATCHET_APP_LIMIT: 200
       HATCHET_DEFAULT_STACK: ${{ matrix.stack }}

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Remove support for Heroku-18. ([#1449](https://github.com/heroku/heroku-buildpack-python/pull/1449))
 
 ## v232 (2023-04-27)
 

README.md

@@ -63,5 +63,5 @@ Supported runtime options include:
 - `python-3.11.3` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)
 - `python-3.10.11` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)
 - `python-3.9.16` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)
-- `python-3.8.16` on Heroku-18 and Heroku-20 only
-- `python-3.7.16` on Heroku-18 and Heroku-20 only
+- `python-3.8.16` on Heroku-20 only
+- `python-3.7.16` on Heroku-20 only

bin/steps/python

@@ -71,35 +71,6 @@ case "${PYTHON_VERSION}" in
   python-3.6.*)
     eol_python_version_error "3.6" "December 23rd, 2021"
     ;;
-  python-3.5.*)
-    eol_python_version_error "3.5" "September 30th, 2020"
-    ;;
-  python-3.4.*)
-    eol_python_version_error "3.4" "March 18th, 2019"
-    ;;
-  python-2.7.*)
-    puts-warn
-    puts-warn "Python 2 reached upstream end-of-life on January 1st, 2020, and is"
-    puts-warn "therefore no longer receiving security updates. Apps still using it"
-    puts-warn "contain potential security vulnerabilities and should be upgraded to"
-    puts-warn "Python 3 as soon as possible."
-    puts-warn
-    puts-warn "In addition, Python 2 is only supported on our oldest stack, Heroku-18,"
-    puts-warn "which is deprecated and reaches end-of-life on April 30th, 2023."
-    puts-warn
-    puts-warn "As such, it is no longer supported by the latest version of this buildpack:"
-    puts-warn "https://devcenter.heroku.com/changelog-items/2473"
-    puts-warn
-    puts-warn "You must either:"
-    puts-warn "  - Upgrade to Python 3 (recommended)"
-    puts-warn "  - Switch to the container stack and use the upstream legacy 'python:2.7' Docker images"
-    puts-warn "  - Switch to an older version of the Python buildpack (short term workaround only)"
-    puts-warn
-    puts-warn "For more details, see:"
-    puts-warn "https://devcenter.heroku.com/articles/python-2-7-eol-faq"
-    puts-warn
-    exit 1
-    ;;
   pypy*)
     puts-warn
     puts-warn "PyPy is no longer supported by the latest version of this buildpack."

builds/build_python_runtime.sh

@@ -9,10 +9,31 @@ INSTALL_DIR="/app/.heroku/python"
 SRC_DIR="/tmp/src"
 ARCHIVES_DIR="/tmp/upload/${STACK}/runtimes"
 
-echo "Building Python ${PYTHON_VERSION} for ${STACK}..."
+case "${STACK}" in
+  heroku-22)
+    SUPPORTED_PYTHON_VERSIONS=(
+      "3.9"
+      "3.10"
+      "3.11"
+    )
+    ;;
+  heroku-20)
+    SUPPORTED_PYTHON_VERSIONS=(
+      "3.7"
+      "3.8"
+      "3.9"
+      "3.10"
+      "3.11"
+    )
+    ;;
+  *)
+    echo "Error: Unsupported stack '${STACK}'!" >&2
+    exit 1
+    ;;
+esac
 
-if [[ "${STACK}" != "heroku-18" && "${STACK}" != "heroku-20" && "${PYTHON_MAJOR_VERSION}" == 3.[7-8] ]]; then
-  echo "Error: Python ${PYTHON_MAJOR_VERSION} is only supported on Heroku-20 and older!" >&2
+if [[ ! " ${SUPPORTED_PYTHON_VERSIONS[*]} " == *" ${PYTHON_MAJOR_VERSION} "* ]]; then
+  echo "Error: Python ${PYTHON_MAJOR_VERSION} is not supported on ${STACK}!" >&2
   exit 1
 fi
 
@@ -36,6 +57,8 @@ case "${PYTHON_MAJOR_VERSION}" in
     ;;
 esac
 
+echo "Building Python ${PYTHON_VERSION} for ${STACK}..."
+
 SOURCE_URL="https://www.python.org/ftp/python/${PYTHON_VERSION}/Python-${PYTHON_VERSION}.tgz"
 SIGNATURE_URL="${SOURCE_URL}.asc"
 
@@ -46,12 +69,8 @@ mkdir -p "${SRC_DIR}" "${INSTALL_DIR}" "${ARCHIVES_DIR}"
 curl --fail --retry 3 --retry-connrefused --connect-timeout 10 --max-time 60 -o python.tgz "${SOURCE_URL}"
 curl --fail --retry 3 --retry-connrefused --connect-timeout 10 --max-time 60 -o python.tgz.asc "${SIGNATURE_URL}"
 
-# Skip GPG verification on Heroku-18 since it fails to fetch keys:
-# `gpg: keyserver receive failed: Server indicated a failure`
-if [[ "${STACK}" != "heroku-18" ]]; then
-  gpg --batch --verbose --recv-keys "${GPG_KEY_FINGERPRINT}"
-  gpg --batch --verify python.tgz.asc python.tgz
-fi
+gpg --batch --verbose --recv-keys "${GPG_KEY_FINGERPRINT}"
+gpg --batch --verify python.tgz.asc python.tgz
 
 tar --extract --file python.tgz --strip-components=1 --directory "${SRC_DIR}"
 cd "${SRC_DIR}"

spec/hatchet/pipenv_spec.rb

@@ -73,80 +73,10 @@
     end
   end
 
-  context 'with a Pipfile.lock containing python_version 2.7' do
-    let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_2.7', allow_failure: true) }
-
-    context 'when using Heroku-18', stacks: %w[heroku-18] do
-      it 'aborts the build with an EOL message' do
-        app.deploy do |app|
-          expect(clean_output(app.output)).to include(<<~OUTPUT)
-            remote: -----> Python app detected
-            remote: -----> Using Python version specified in Pipfile.lock
-            remote:  !     
-            remote:  !     Python 2 reached upstream end-of-life on January 1st, 2020, and is
-            remote:  !     therefore no longer receiving security updates. Apps still using it
-            remote:  !     contain potential security vulnerabilities and should be upgraded to
-            remote:  !     Python 3 as soon as possible.
-            remote:  !     
-            remote:  !     In addition, Python 2 is only supported on our oldest stack, Heroku-18,
-            remote:  !     which is deprecated and reaches end-of-life on April 30th, 2023.
-            remote:  !     
-            remote:  !     As such, it is no longer supported by the latest version of this buildpack:
-            remote:  !     https://devcenter.heroku.com/changelog-items/2473
-            remote:  !     
-            remote:  !     You must either:
-            remote:  !       - Upgrade to Python 3 (recommended)
-            remote:  !       - Switch to the container stack and use the upstream legacy 'python:2.7' Docker images
-            remote:  !       - Switch to an older version of the Python buildpack (short term workaround only)
-            remote:  !     
-            remote:  !     For more details, see:
-            remote:  !     https://devcenter.heroku.com/articles/python-2-7-eol-faq
-            remote:  !     
-          OUTPUT
-        end
-      end
-    end
-
-    context 'when using Heroku-20 or newer', stacks: %w[heroku-20 heroku-22] do
-      # Python 2.7 is EOL, so has not been built for newer stacks.
-      include_examples 'aborts the build with a runtime not available message (Pipenv)', '2.7.18'
-    end
-  end
-
-  context 'with a Pipfile.lock containing python_version 3.5' do
-    let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_3.5', allow_failure: true) }
-
-    context 'when using Heroku-18', stacks: %w[heroku-18] do
-      it 'aborts the build with an EOL message' do
-        app.deploy do |app|
-          expect(clean_output(app.output)).to include(<<~OUTPUT)
-            remote: -----> Python app detected
-            remote: -----> Using Python version specified in Pipfile.lock
-            remote:  !     
-            remote:  !     Python 3.5 reached upstream end-of-life on September 30th, 2020, and is
-            remote:  !     therefore no longer receiving security updates:
-            remote:  !     https://devguide.python.org/versions/#supported-versions
-            remote:  !     
-            remote:  !     As such, it is no longer supported by the latest version of this buildpack.
-            remote:  !     
-            remote:  !     Please upgrade to a newer Python version. See:
-            remote:  !     https://devcenter.heroku.com/articles/python-runtimes
-            remote:  !     
-          OUTPUT
-        end
-      end
-    end
-
-    context 'when using Heroku-20 or newer', stacks: %w[heroku-20 heroku-22] do
-      # Python 3.5 is EOL, so has not been built for newer stacks.
-      include_examples 'aborts the build with a runtime not available message (Pipenv)', '3.5.10'
-    end
-  end
-
   context 'with a Pipfile.lock containing python_version 3.6' do
     let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_3.6', allow_failure: true) }
 
-    context 'when using Heroku-18 or Heroku-20', stacks: %w[heroku-18 heroku-20] do
+    context 'when using Heroku-20', stacks: %w[heroku-20] do
       it 'aborts the build with an EOL message' do
         app.deploy do |app|
           expect(clean_output(app.output)).to match(Regexp.new(<<~OUTPUT))
@@ -177,7 +107,7 @@
     let(:allow_failure) { false }
     let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_3.7', allow_failure:) }
 
-    context 'when using Heroku-18 or Heroku-20', stacks: %w[heroku-18 heroku-20] do
+    context 'when using Heroku-20', stacks: %w[heroku-20] do
       it 'builds with the latest Python 3.7 but shows a deprecation warning' do
         app.deploy do |app|
           expect(clean_output(app.output)).to match(Regexp.new(<<~REGEX))
@@ -213,7 +143,7 @@
     let(:allow_failure) { false }
     let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_3.8', allow_failure:) }
 
-    context 'when using Heroku-18 or Heroku-20', stacks: %w[heroku-18 heroku-20] do
+    context 'when using Heroku-20', stacks: %w[heroku-20] do
       include_examples 'builds using Pipenv with the requested Python version', LATEST_PYTHON_3_8
     end
 

spec/hatchet/python_update_warning_spec.rb

@@ -60,7 +60,7 @@
     let(:allow_failure) { false }
     let(:app) { Hatchet::Runner.new('spec/fixtures/python_3.7_outdated', allow_failure:) }
 
-    context 'when using Heroku-18 or Heroku-20', stacks: %w[heroku-18 heroku-20] do
+    context 'when using Heroku-20', stacks: %w[heroku-20] do
       it 'warns about both the deprecated major version and the patch update' do
         app.deploy do |app|
           expect(clean_output(app.output)).to match(Regexp.new(<<~REGEX))
@@ -95,7 +95,7 @@
     let(:allow_failure) { false }
     let(:app) { Hatchet::Runner.new('spec/fixtures/python_3.8_outdated', allow_failure:) }
 
-    context 'when using Heroku-18 or Heroku-20', stacks: %w[heroku-18 heroku-20] do
+    context 'when using Heroku-20', stacks: %w[heroku-20] do
       include_examples 'warns there is a Python update available', '3.8.12', LATEST_PYTHON_3_8
     end