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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: 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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,4 @@ | ||
| pub(crate) mod pip; | ||
| pub(crate) mod pip_cache; | ||
| pub(crate) mod pip_dependencies; | ||
| pub(crate) mod python; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,143 @@ | ||
| use crate::packaging_tool_versions::PIP_VERSION; | ||
| use crate::python_version::PythonVersion; | ||
| use crate::utils::StreamedCommandError; | ||
| use crate::{utils, BuildpackError, PythonBuildpack}; | ||
| use libcnb::build::BuildContext; | ||
| use libcnb::data::layer_name; | ||
| use libcnb::layer::{ | ||
| CachedLayerDefinition, EmptyLayerCause, InvalidMetadataAction, LayerState, RestoredLayerAction, | ||
| }; | ||
| use libcnb::layer_env::{LayerEnv, ModificationBehavior, Scope}; | ||
| use libcnb::Env; | ||
| use libherokubuildpack::log::log_info; | ||
| use serde::{Deserialize, Serialize}; | ||
| use std::io; | ||
| use std::path::Path; | ||
| use std::process::Command; | ||
|
|
||
| /// Creates a layer containing pip. | ||
| pub(crate) fn install_pip( | ||
| context: &BuildContext<PythonBuildpack>, | ||
| env: &mut Env, | ||
| python_version: &PythonVersion, | ||
| python_layer_path: &Path, | ||
| ) -> Result<(), libcnb::Error<BuildpackError>> { | ||
| let new_metadata = PipLayerMetadata { | ||
| python_version: python_version.to_string(), | ||
| pip_version: PIP_VERSION.to_string(), | ||
| }; | ||
|
|
||
| let layer = context.cached_layer( | ||
| layer_name!("pip"), | ||
| CachedLayerDefinition { | ||
| build: true, | ||
| launch: true, | ||
| invalid_metadata_action: &|_| InvalidMetadataAction::DeleteLayer, | ||
| restored_layer_action: &|cached_metadata: &PipLayerMetadata, _| { | ||
| let cached_pip_version = cached_metadata.pip_version.clone(); | ||
| if cached_metadata == &new_metadata { | ||
| (RestoredLayerAction::KeepLayer, cached_pip_version) | ||
| } else { | ||
| (RestoredLayerAction::DeleteLayer, cached_pip_version) | ||
| } | ||
| }, | ||
| }, | ||
| )?; | ||
|
|
||
| let mut layer_env = LayerEnv::new() | ||
| // We use a curated pip version, so disable the update check to speed up pip invocations, | ||
| // reduce build log spam and prevent users from thinking they need to manually upgrade. | ||
| // https://pip.pypa.io/en/stable/cli/pip/#cmdoption-disable-pip-version-check | ||
| .chainable_insert( | ||
| Scope::All, | ||
| ModificationBehavior::Override, | ||
| "PIP_DISABLE_PIP_VERSION_CHECK", | ||
| "1", | ||
| ) | ||
| // Move the Python user base directory to this layer instead of under HOME: | ||
| // https://docs.python.org/3/using/cmdline.html#envvar-PYTHONUSERBASE | ||
| .chainable_insert( | ||
| Scope::All, | ||
| ModificationBehavior::Override, | ||
| "PYTHONUSERBASE", | ||
| layer.path(), | ||
| ); | ||
|
|
||
| match layer.state { | ||
| LayerState::Restored { | ||
| cause: ref cached_pip_version, | ||
| } => { | ||
| log_info(format!("Using cached pip {cached_pip_version}")); | ||
| } | ||
| LayerState::Empty { ref cause } => { | ||
| match cause { | ||
| EmptyLayerCause::InvalidMetadataAction { .. } => { | ||
| log_info("Discarding cached pip since its layer metadata can't be parsed"); | ||
| } | ||
| EmptyLayerCause::RestoredLayerAction { | ||
| cause: cached_pip_version, | ||
| } => { | ||
| log_info(format!("Discarding cached pip {cached_pip_version}")); | ||
| } | ||
| EmptyLayerCause::NewlyCreated => {} | ||
| } | ||
|
|
||
| log_info(format!("Installing pip {PIP_VERSION}")); | ||
|
|
||
| // We use the pip wheel bundled within Python's standard library to install our chosen | ||
| // pip version, since it's faster than `ensurepip` followed by an upgrade in place. | ||
| let bundled_pip_module_path = | ||
| utils::bundled_pip_module_path(python_layer_path, python_version) | ||
| .map_err(PipLayerError::LocateBundledPip)?; | ||
|
|
||
| utils::run_command_and_stream_output( | ||
| Command::new("python") | ||
| .args([ | ||
| &bundled_pip_module_path.to_string_lossy(), | ||
| "install", | ||
| // There is no point using pip's cache here, since the layer itself will be cached. | ||
| "--no-cache-dir", | ||
| "--no-input", | ||
| "--no-warn-script-location", | ||
| "--quiet", | ||
| "--user", | ||
| format!("pip=={PIP_VERSION}").as_str(), | ||
| ]) | ||
| .env_clear() | ||
| .envs(&layer_env.apply(Scope::Build, env)), | ||
| ) | ||
| .map_err(PipLayerError::InstallPipCommand)?; | ||
|
|
||
| layer.write_metadata(new_metadata)?; | ||
| } | ||
| } | ||
|
|
||
| layer.write_env(&layer_env)?; | ||
| // Required to pick up the automatic PATH env var. See: https://github.com/heroku/libcnb.rs/issues/842 | ||
| layer_env = layer.read_env()?; | ||
| env.clone_from(&layer_env.apply(Scope::Build, env)); | ||
|
|
||
| Ok(()) | ||
| } | ||
|
|
||
| // pip's wheel is a pure Python package with no dependencies, so the layer is not arch or distro | ||
| // specific. However, the generated .pyc files vary by Python version. | ||
| #[derive(Deserialize, PartialEq, Serialize)] | ||
| #[serde(deny_unknown_fields)] | ||
| struct PipLayerMetadata { | ||
| python_version: String, | ||
| pip_version: String, | ||
| } | ||
|
|
||
| /// Errors that can occur when installing pip into a layer. | ||
| #[derive(Debug)] | ||
| pub(crate) enum PipLayerError { | ||
| InstallPipCommand(StreamedCommandError), | ||
| LocateBundledPip(io::Error), | ||
| } | ||
|
|
||
| impl From<PipLayerError> for libcnb::Error<BuildpackError> { | ||
| fn from(error: PipLayerError) -> Self { | ||
| Self::BuildpackError(BuildpackError::PipLayer(error)) | ||
| } | ||
| } |
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