Deprecate support for the runtime.txt file
#325
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The `runtime.txt` file is a classic Heroku Python buildpack invention that's not widely supported in the Python ecosystem. Instead, most other tooling (pyenv, package managers, GitHub Actions, dependency update bots etc) support/use the `.python-version` file. As such, we recently added `.python-version` support to both the Python CNB and the classic Python buildpack, and updated all documentation and guides to use it instead of the `runtime.txt` file. eg: https://devcenter.heroku.com/articles/python-runtimes We would prefer apps use the new file, since it helps ensure their deployed app is using the same Python version used locally (via eg pyenv or uv) or in CI. As such this adds a deprecation warning for apps using `runtime.txt`, which will be made an error in the CNB in near future (likely before Fir GA). We'll also be adding a deprecation warning to the classic Python buildpack, however, won't be making that an error any time soon (if at all). Towards #275. GUS-W-16878239.
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runesoerensen
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## heroku/python ### Added - Added `runtime.txt` support for the `python-3.X` major Python version form. ([#322](#322)) - Enabled `libcnb`'s `trace` feature. ([#320](#320)) ### Changed - The Python 3.13 version alias now resolves to Python 3.13.2. ([#326](#326)) - The Python 3.12 version alias now resolves to Python 3.12.9. ([#326](#326)) - Deprecated support for the `runtime.txt` file. ([#325](#325)) - Improved the error messages shown when the `.python-version` file contents aren't valid. ([#325](#325))
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## heroku/python ### Added - Added `runtime.txt` support for the `python-3.X` major Python version form. ([#322](heroku/buildpacks-python#322)) - Enabled `libcnb`'s `trace` feature. ([#320](heroku/buildpacks-python#320)) ### Changed - The Python 3.13 version alias now resolves to Python 3.13.2. ([#326](heroku/buildpacks-python#326)) - The Python 3.12 version alias now resolves to Python 3.12.9. ([#326](heroku/buildpacks-python#326)) - Deprecated support for the `runtime.txt` file. ([#325](heroku/buildpacks-python#325)) - Improved the error messages shown when the `.python-version` file contents aren't valid. ([#325](heroku/buildpacks-python#325))
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The
runtime.txtfile is a classic Heroku Python buildpack invention that's not widely supported in the Python ecosystem. Instead, most other tooling (pyenv, package managers, GitHub Actions, dependency update bots etc) support/use the.python-versionfile.As such, we recently added
.python-versionsupport to both the Python CNB and the classic Python buildpack, and updated all documentation and guides to use it instead of theruntime.txtfile. eg:https://devcenter.heroku.com/articles/python-runtimes
We would prefer apps use the new file, since it helps ensure their deployed app is using the same Python version used locally (via eg pyenv or uv) or in CI.
As such this adds a deprecation warning for apps using
runtime.txt, which will be made an error in the CNB in near future (likely before Fir GA). We'll also be adding a deprecation warning to the classic Python buildpack, however, won't be making that an error any time soon (and maybe at all; but TBD).Towards #275.
GUS-W-16878239.