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Change-Id: Ie1a32cda67f94b0a2b3329b1be9e03dcbedf39cc Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/400917 Reviewed-by: Josip Sokcevic <sokcevic@google.com> Tested-by: Mike Frysinger <vapier@google.com> Commit-Queue: Mike Frysinger <vapier@google.com>
93 lines
3.8 KiB
Markdown
93 lines
3.8 KiB
Markdown
# Supported Python Versions
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This documents the current supported Python versions, and tries to provide
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guidance for when we decide to drop support for older versions.
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## Summary
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* Python 3.6 (released Dec 2016) is required starting with repo-2.0.
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* Older versions of Python (e.g. v2.7) may use old releases via the repo-1.x
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branch, but no support is provided.
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## repo hooks
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Projects that use [repo hooks] run on independent schedules.
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Since it's not possible to detect what version of Python the hooks were written
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or tested against, we always import & exec them with the active Python version.
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If the user's Python is too new for the [repo hooks], then it is up to the hooks
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maintainer to update.
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## Repo launcher
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The [repo launcher] is an independent script that can support older versions of
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Python without holding back the rest of the codebase.
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If it detects the current version of Python is too old, it will try to reexec
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via a newer version of Python via standard `pythonX.Y` interpreter names.
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However, this is provided as a nicety when it is not onerous, and there is no
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official support for older versions of Python than the rest of the codebase.
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If your default python interpreters are too old to run the launcher even though
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you have newer versions installed, your choices are:
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* Modify the [repo launcher]'s shebang to suite your environment.
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* Download an older version of the [repo launcher] and don't upgrade it.
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Be aware that we do not guarantee old repo launchers will work with current
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versions of repo. Bug reports using old launchers will not be accepted.
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## When to drop support
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So far, Python 3.6 has provided most of the interesting features that we want
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(e.g. typing & f-strings), and there haven't been features in newer versions
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that are critical to us.
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That said, let's assume we need functionality that only exists in Python 3.7.
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How do we decide when it's acceptable to drop Python 3.6?
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1. Review the [Project References](./release-process.md#project-references) to
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see what major distros are using the previous version of Python, and when
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they go EOL. Generally we care about Ubuntu LTS & current/previous Debian
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stable versions.
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* If they're all EOL already, then go for it, drop support.
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* If they aren't EOL, start a thread on [repo-discuss] to see how the user
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base feels about the proposal.
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1. Update the "soft" versions in the codebase. This will start warning users
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that the older version is deprecated.
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* Update [repo](/repo) if the launcher needs updating.
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This only helps with people who download newer launchers.
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* Update [main.py](/main.py) for the main codebase.
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This warns for everyone regardless of [repo launcher] version.
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* Update [requirements.json](/requirements.json).
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This allows [repo launcher] to display warnings/errors without having
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to execute the new codebase. This helps in case of syntax or module
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changes where older versions won't even be able to import the new code.
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1. After some grace period (ideally at least 2 quarters after the first release
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with the updated soft requirements), update the "hard" versions, and then
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start using the new functionality.
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## Python 2.7 & 3.0-3.5
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> **There is no support for these versions.**
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> **Do not file bugs if you are using old Python versions.**
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> **Any such reports will be marked invalid and ignored.**
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> **Upgrade your distro and/or runtime instead.**
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Fetch an old version of the [repo launcher]:
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```sh
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$ curl https://storage.googleapis.com/git-repo-downloads/repo-2.32 > ~/.bin/repo-2.32
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$ chmod a+rx ~/.bin/repo-2.32
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```
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Then initialize an old version of repo:
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```sh
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$ repo-2.32 init --repo-rev=repo-1 ...
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```
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[repo-discuss]: https://groups.google.com/forum/#!forum/repo-discuss
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[repo hooks]: ./repo-hooks.md
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[repo launcher]: ../repo
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