Drop Python 3.7 support and adopt a formal policy for supported Pytho…

…n versions (#3740)

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
+        python: ['3.8', '3.9', '3.10', '3.11', '3.12']
         image:
           - ubuntu-latest
         include:

CHANGES.txt

@@ -10,6 +10,15 @@ Bugfixes
 * Fix the new plugin manager not loading plugins if the plugin folder is a symlink (Issue #3741)
 * Fix the ``nikola plugin`` command not working (Issue #3736)
 
+Other
+-----
+
+* Nikola now requires Python 3.8 or newer.
+* Nikola has adopted a policy for Python version support,
+  promising support for versions supported by the Python core team,
+  Ubuntu LTS, or Debian stable, and taking into consideration
+  Debian oldstable and PyPy.
+
 New in v8.3.0
 =============
 

README.rst

@@ -37,7 +37,7 @@ It has many features, but here are some of the nicer ones:
 * Syntax highlighting for almost any programming language or markup
 * Multilingual sites, `translated to 50 languages.`__
 * Doesn't reinvent wheels, leverages existing tools.
-* Python 3.7+ compatible.
+* Python 3.8+ compatible.
 
 .. _Nikola Handbook: https://getnikola.com/handbook.html#why-static
 __ https://users.getnikola.com/

docs/manual.rst

@@ -134,7 +134,7 @@ Obsolescence
     You may say those are long term issues, or that they won't matter for years. Well,
     I believe things should work forever, or as close to it as we can make them.
     Nikola's static output and its input files will work as long as you can install
-    Python 3.7 or newer under Linux, Windows, or macOS and can find a server
+    Python 3.8 or newer under Linux, Windows, or macOS and can find a server
     that sends files over HTTP. That's probably 10 or 15 years at least.
 
     Also, static sites are easily handled by the Internet Archive.

docs/python-version-support-policy.rst

@@ -0,0 +1,88 @@
+.. title: Python version support policy
+.. slug: python-version-support-policy
+.. date: 2024-01-13 10:00:00 UTC
+.. author: The Nikola Team
+
+Nikola is written in Python. New Python versions are released
+`every year in October.`__ New Python versions bring new language and standard
+library features, but they also often remove things the Python development team
+considered old/deprecated/uncool, and some libraries with C dependencies often
+cause issues (they fail to build or they lack binary wheels on PyPI) for
+shortly after a new Python version. The Python team supports a release for 5
+years after the initial release (3.x.0).
+
+__ https://peps.python.org/pep-0602/
+
+Nikola is used by both Python developers who are using the latest-and-greatest
+Python release, and more casual Python users that use whatever release is
+provided by their Unix-like operating system of choice. Some of them may be
+using rolling-release or often-updated Linux distributions, like Arch Linux or
+Fedora; others might be on Ubuntu LTS or Debian stable.
+
+In order to support the largest group of users, while also keeping the list
+of supported Python releases manageable, and minimizing the number of cases
+where legacy or worse code must be used to support old versions, the following
+Python version support policy is adopted.
+
+Policy
+======
+
+1. Nikola *must* support all Python versions for which at least one of those criteria is true:
+
+   a. It is `supported by the Python core team`__ (5 years since release).
+   b. It is `included`__ in the oldest `Ubuntu LTS release`__  still within standard support (LTS releases are supported for 5 years since release).
+   c. It is included in `Debian stable`__.
+   d. It is included in `Debian oldstable`__, if the that Debian release became oldstable in the past 3 months.
+
+2. Nikola *should* support all Python versions for which at least one of those criteria is true:
+
+   a. It is `the newest Python release supported by PyPy`__.
+   b. It is included in Debian oldstable, if that Debian release has been oldstable since more than 3 months.
+
+3. If a Python version is covered only by the optional criteria, the Nikola maintainers may decide to drop support for it if it is not feasible to maintain.
+
+4. Nikola should also support Python versions that are intermediate versions between the oldest supported version and the latest version.
+   For example, if the latest Python version is 3.9, the oldest officially supported version is 3.7, the but the oldest Ubuntu LTS and Debian stable both have 3.4, then Python 3.5 and 3.6 should *also* be supported.
+
+5. CI pipelines on Linux should be run for all supported Python versions. CI pipelines for Windows and macOS should be run for the latest Python version.
+
+6. In the event Nikola does not support the newest Python release, the relevant issues should be resolved or reported upstream as soon as possible, in consideration of rolling-release distributions that package Nikola.
+
+7. If all mandatory criteria stop applying to a Python version, it may be dropped after a grace period of 3 months. (This means that Debian oldstable is guaranteed support for a total of 6 months.)
+
+8. If all optional criteria stop applying to a Python version, and all mandatory criteria were already inapplicable, it may be dropped after a grace period of 6 weeks.
+
+9. Removing support for a Python version does not require any form of advance warning to Nikola users and may be done in a patch version.
+
+10. Maintainers may choose to support a Python version, even if it does not fit any of the above criteria or rules, if there exist other significant groups of Python users that may benefit from support for that version, as long as that version would not add undue burden.
+
+Support Matrix
+==============
+
+Criteria
+--------
+
+Data as of January 2024.
+
+* Python Core Team: Python 3.7 supported until 2023-06, Python 3.8 supported until 2024-10, Python 3.9 supported until 2025-10, Python 3.10 supported until 2026-10
+* Ubuntu LTS: Python 3.8 supported by Ubuntu 20.04 until 2025-04, Python 3.10 supported by Ubuntu 22.04 until 2027-04
+* Debian stable: Python 3.11 in bookworm
+* Debian oldstable: Python 3.9 in bullseye, became oldstable in 2023-06
+* PyPy: latest supported version is 3.10
+
+Applied to Python versions
+--------------------------
+
+* Python 3.7: no criteria apply since 2023-09, support dropped in 2024-01
+* Python 3.8: expected to be supported until at least 2025-07 via Ubuntu 20.04 LTS
+* Python 3.9: expected to be supported until at least 2026-01 via Python Core Team (+ possibly Debian oldstable)
+* Python 3.10: expected to be supported until at least 2027-07 via Ubuntu 20.04 (+ possibly PyPy)
+* Python 3.11: until at least 2028-01, might be extended by Debian stable (bookworm) and Ubuntu 24.04 (noble)
+* Python 3.12: current release; until at least 2029-01, might be extended by Ubuntu 24.04 (noble)
+
+__ https://devguide.python.org/versions/
+__ https://packages.ubuntu.com/search?suite=all&exact=1&searchon=names&keywords=python3
+__ https://wiki.ubuntu.com/Releases
+__ https://packages.debian.org/stable/python3
+__ https://packages.debian.org/oldstable/python3
+__ https://www.pypy.org/

setup.py

@@ -24,8 +24,8 @@
 # ########## platform specific stuff #############
 if sys.version_info[0] == 2:
     raise Exception('Python 2 is not supported')
-elif sys.version_info[0] == 3 and sys.version_info[1] < 7:
-    raise Exception('Python 3 version < 3.7 is not supported')
+elif sys.version_info[0] == 3 and sys.version_info[1] < 8:
+    raise Exception('Python 3 version < 3.8 is not supported')
 
 ##################################################
 
@@ -128,7 +128,6 @@ def run(self):
                    'Operating System :: POSIX',
                    'Operating System :: Unix',
                    'Programming Language :: Python',
-                   'Programming Language :: Python :: 3.7',
                    'Programming Language :: Python :: 3.8',
                    'Programming Language :: Python :: 3.9',
                    'Programming Language :: Python :: 3.10',
@@ -140,7 +139,7 @@ def run(self):
       install_requires=dependencies,
       extras_require=extras,
       include_package_data=True,
-      python_requires='>=3.7',
+      python_requires='>=3.8',
       cmdclass={'install': nikola_install, 'build_py': nikola_build_py},
       data_files=[
               ('share/doc/nikola', [