Add support for Python 3.12 (#1490)

And release Python 3.12.0. The default Python version remains
unchanged (at 3.11.x) for now.

Release announcement:
https://blog.python.org/2023/10/python-3120-final-now-available.html
https://www.python.org/downloads/release/python-3120/

Details on what's new in Python 3.12:
https://docs.python.org/3.12/whatsnew/3.12.html

Binary builds on GitHub Actions:
https://github.com/heroku/heroku-buildpack-python/actions/runs/6382585145

GUS-W-12345517.
GUS-W-12345519.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Added support for Python 3.12. ([#1490](https://github.com/heroku/heroku-buildpack-python/pull/1490))
 
 ## v235 (2023-08-25)
 

README.md

@@ -60,6 +60,7 @@ Specify a Python Runtime
 
 Supported runtime options include:
 
+- `python-3.12.0` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)
 - `python-3.11.5` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)
 - `python-3.10.13` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)
 - `python-3.9.18` on all [supported stacks](https://devcenter.heroku.com/articles/stack#stack-support-details)

bin/default_pythons

@@ -5,6 +5,7 @@
 # the env vars to subprocesses.
 # shellcheck disable=2034
 
+LATEST_312="python-3.12.0"
 LATEST_311="python-3.11.5"
 LATEST_310="python-3.10.13"
 LATEST_39="python-3.9.18"

bin/steps/pipenv-python-version

@@ -49,6 +49,9 @@ if [[ -f $BUILD_DIR/Pipfile ]]; then
                     3.11)
                         echo "${LATEST_311}" > "${BUILD_DIR}/runtime.txt"
                         ;;
+                    3.12)
+                        echo "${LATEST_312}" > "${BUILD_DIR}/runtime.txt"
+                        ;;
                 esac
             fi
 

bin/steps/python

@@ -45,6 +45,9 @@ function warn_if_patch_update_available() {
 }
 
 case "${PYTHON_VERSION}" in
+  python-3.12.*)
+    warn_if_patch_update_available "${PYTHON_VERSION}" "${LATEST_312}"
+    ;;
   python-3.11.*)
     warn_if_patch_update_available "${PYTHON_VERSION}" "${LATEST_311}"
     ;;

builds/build_python_runtime.sh

@@ -20,6 +20,7 @@ case "${STACK}" in
       "3.9"
       "3.10"
       "3.11"
+      "3.12"
     )
     ;;
   heroku-20)
@@ -28,6 +29,7 @@ case "${STACK}" in
       "3.9"
       "3.10"
       "3.11"
+      "3.12"
     )
     ;;
   *)
@@ -41,6 +43,10 @@ fi
 
 # The release keys can be found on https://www.python.org/downloads/ -> "OpenPGP Public Keys".
 case "${PYTHON_MAJOR_VERSION}" in
+  3.12)
+    # https://github.com/Yhg1s.gpg
+    GPG_KEY_FINGERPRINT='7169605F62C751356D054A26A821E680E5FA6305'
+    ;;
   3.10|3.11)
     # https://keybase.io/pablogsal/
     GPG_KEY_FINGERPRINT='A035C8C19219BA821ECEA86B64E628F8D684696D'
@@ -115,7 +121,7 @@ if [[ "${PYTHON_MAJOR_VERSION}" != 3.[8-9] ]]; then
   )
 fi
 
-if [[ "${PYTHON_MAJOR_VERSION}" == "3.11" ]]; then
+if [[ "${PYTHON_MAJOR_VERSION}" == "3.11" || "${PYTHON_MAJOR_VERSION}" == "3.12" ]]; then
   CONFIGURE_OPTS+=(
     # Skip building the test modules, since we remove them after the build anyway.
     # This feature was added in Python 3.10+, however it wasn't until Python 3.11

spec/fixtures/pipenv_python_3.12/Pipfile

@@ -0,0 +1,12 @@
+[[source]]
+url = "https://pypi.org/simple"
+verify_ssl = true
+name = "pypi"
+
+[packages]
+urllib3 = "*"
+
+[dev-packages]
+
+[requires]
+python_version = "3.12"

spec/fixtures/python_3.12/requirements.txt

@@ -0,0 +1 @@
+urllib3

spec/fixtures/python_3.12/runtime.txt

@@ -0,0 +1 @@
+python-3.12.0

spec/hatchet/pipenv_spec.rb

@@ -174,6 +174,12 @@
     include_examples 'builds using Pipenv with the requested Python version', LATEST_PYTHON_3_11
   end
 
+  context 'with a Pipfile.lock containing python_version 3.12' do
+    let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_3.12') }
+
+    include_examples 'builds using Pipenv with the requested Python version', LATEST_PYTHON_3_12
+  end
+
   context 'with a Pipfile.lock containing python_full_version 3.10.7' do
     let(:allow_failure) { false }
     let(:app) { Hatchet::Runner.new('spec/fixtures/pipenv_python_full_version', allow_failure:) }

spec/hatchet/python_update_warning_spec.rb

@@ -127,4 +127,6 @@
 
     include_examples 'warns there is a Python update available', '3.11.0', LATEST_PYTHON_3_11
   end
+
+  # TODO: Add a Python 3.12.0 outdated test once Python 3.12.1 is released.
 end

spec/hatchet/python_version_spec.rb

@@ -181,6 +181,12 @@
     include_examples 'builds with the requested Python version', LATEST_PYTHON_3_11
   end
 
+  context 'when runtime.txt contains python-3.12.0' do
+    let(:app) { Hatchet::Runner.new('spec/fixtures/python_3.12') }
+
+    include_examples 'builds with the requested Python version', LATEST_PYTHON_3_12
+  end
+
   context 'when runtime.txt contains pypy3.6-7.3.2' do
     let(:app) { Hatchet::Runner.new('spec/fixtures/pypy_3.6', allow_failure: true) }
 

spec/spec_helper.rb

@@ -11,6 +11,7 @@
 LATEST_PYTHON_3_9 = '3.9.18'
 LATEST_PYTHON_3_10 = '3.10.13'
 LATEST_PYTHON_3_11 = '3.11.5'
+LATEST_PYTHON_3_12 = '3.12.0'
 DEFAULT_PYTHON_VERSION = LATEST_PYTHON_3_11
 
 # The requirement versions are effectively buildpack constants, however, we want