Move pip into its own layer #258
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pip is now installed into its own layer (as a user site-packages install) instead of into system site-packages in the Python layer. This is possible now that the user site-packages is no longer being used for app dependencies, after the switch to venvs in #257. pip being in its own layer has the following advantages: 1. We can more easily exclude pip from the build/run images when using other packages managers (such as for the upcoming Poetry support). 2. A change in pip version no longer unnecessarily invalidates the Python layer. 3. In the future we could more easily exclude pip from the run image entirely, should we wish (see #255). This has been split out of the Poetry PR for easier review. Closes #254. GUS-W-16616956.
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The Python package manager Poetry is now supported for installing app dependencies: https://python-poetry.org To use Poetry, apps must have a `poetry.lock` lockfile, which can be created by running `poetry lock` locally, after adding Poetry config to `pyproject.toml` (which can be done either manually or by using `poetry init`). Apps must only have one package manager file (either `requirements.txt` or `poetry.lock`, but not both) otherwise the buildpack will abort the build with an error (which will help prevent some of the types of support tickets we see in the classic buildpack with users unknowingly mixing and matching pip + Pipenv). Poetry is installed into a build-only layer (to reduce the final app image size), so is not available at run-time. The app dependencies are installed into a virtual environment (the same as for pip after #257, for the reasons described in #253), which is on `PATH` so does not need explicit activation when using the app image. As such, use of `poetry run` or `poetry shell` is not required at run-time to use dependencies in the environment. When using Poetry, pip is not installed (possible thanks to #258), since Poetry includes its own internal vendored copy that it will use instead (for the small number of Poetry operations for which it still calls out to pip, such as package uninstalls). Both the Poetry and app dependencies layers are cached, however, the Poetry download/wheel cache is not cached, since using it is slower than caching the dependencies layer (for more details see the comments on `poetry_dependencies::install_dependencies`). The `poetry install --sync` command is run using `--only main` so as to only install the main `[tool.poetry.dependencies]` dependencies group from `pyproject.toml`, and not any of the app's other dependency groups (such as test/dev groups, eg `[tool.poetry.group.test.dependencies]`). I've marked this `semver: major` since in the (probably unlikely) event there are any early-adopter projects using this CNB that have both a `requirements.txt` and `poetry.lock` then this change will cause them to error (until one of the files is deleted). Relevant Poetry docs: - https://python-poetry.org/docs/cli/#install - https://python-poetry.org/docs/configuration/ - https://python-poetry.org/docs/managing-dependencies/#dependency-groups Work that will be handled later: - Support for selecting Python version via `tool.poetry.dependencies.python`: #260 - Build output and error messages polish/CX review (this will be performed when switching the buildpack to the new logging style). - More detailed user-facing docs: #11 Closes #7. GUS-W-9607867. GUS-W-9608286. GUS-W-9608295.
edmorley
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The Python package manager Poetry is now supported for installing app dependencies: https://python-poetry.org To use Poetry, apps must have a `poetry.lock` lockfile, which can be created by running `poetry lock` locally, after adding Poetry config to `pyproject.toml` (which can be done either manually or by using `poetry init`). Apps must only have one package manager file (either `requirements.txt` or `poetry.lock`, but not both) otherwise the buildpack will abort the build with an error (which will help prevent some of the types of support tickets we see in the classic buildpack with users unknowingly mixing and matching pip + Pipenv). Poetry is installed into a build-only layer (to reduce the final app image size), so is not available at run-time. The app dependencies are installed into a virtual environment (the same as for pip after #257, for the reasons described in #253), which is on `PATH` so does not need explicit activation when using the app image. As such, use of `poetry run` or `poetry shell` is not required at run-time to use dependencies in the environment. When using Poetry, pip is not installed (possible thanks to #258), since Poetry includes its own internal vendored copy that it will use instead (for the small number of Poetry operations for which it still calls out to pip, such as package uninstalls). Both the Poetry and app dependencies layers are cached, however, the Poetry download/wheel cache is not cached, since using it is slower than caching the dependencies layer (for more details see the comments on `poetry_dependencies::install_dependencies`). The `poetry install --sync` command is run using `--only main` so as to only install the main `[tool.poetry.dependencies]` dependencies group from `pyproject.toml`, and not any of the app's other dependency groups (such as test/dev groups, eg `[tool.poetry.group.test.dependencies]`). I've marked this `semver: major` since in the (probably unlikely) event there are any early-adopter projects using this CNB that have both a `requirements.txt` and `poetry.lock` then this change will cause them to error (until one of the files is deleted). Relevant Poetry docs: - https://python-poetry.org/docs/cli/#install - https://python-poetry.org/docs/configuration/ - https://python-poetry.org/docs/managing-dependencies/#dependency-groups Work that will be handled later: - Support for selecting Python version via `tool.poetry.dependencies.python`: #260 - Build output and error messages polish/CX review (this will be performed when switching the buildpack to the new logging style). - More detailed user-facing docs: #11 Closes #7. GUS-W-9607867. GUS-W-9608286. GUS-W-9608295.
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pip is now installed into its own layer (as a user site-packages install) instead of into system site-packages in the Python layer.
This is possible now that the user site-packages location is no longer being used for app dependencies, after the switch to venvs in #257.
pip being in its own layer has the following advantages:
This has been split out of the Poetry PR for easier review.
Closes #254.
GUS-W-16616956.