build.go

package pipinstall

import (
	"os"
	"time"

	"github.com/paketo-buildpacks/packit/v2"
	"github.com/paketo-buildpacks/packit/v2/chronos"
	"github.com/paketo-buildpacks/packit/v2/draft"
	"github.com/paketo-buildpacks/packit/v2/fs"
	"github.com/paketo-buildpacks/packit/v2/sbom"
	"github.com/paketo-buildpacks/packit/v2/scribe"
)

//go:generate faux --interface EntryResolver --output fakes/entry_resolver.go
//go:generate faux --interface InstallProcess --output fakes/install_process.go
//go:generate faux --interface SitePackagesProcess --output fakes/site_packages_process.go
//go:generate faux --interface SBOMGenerator --output fakes/sbom_generator.go

// EntryResolver defines the interface for picking the most relevant entry from
// the Buildpack Plan entries.
type EntryResolver interface {
	MergeLayerTypes(name string, entries []packit.BuildpackPlanEntry) (launch, build bool)
}

// InstallProcess defines the interface for installing the pip dependencies.
type InstallProcess interface {
	Execute(workingDir, targetDir, cacheDir string) error
}

// SitePackagesProcess defines the interface for determining the site-packages path.
type SitePackagesProcess interface {
	Execute(layerPath string) (sitePackagesPath string, err error)
}

type SBOMGenerator interface {
	Generate(dir string) (sbom.SBOM, error)
}

// Build will return a packit.BuildFunc that will be invoked during the build
// phase of the buildpack lifecycle.
//
// Build will install the pip dependencies by using the requirements.txt file
// to a packages layer. It also makes use of a cache layer to reuse the pip
// cache.
func Build(installProcess InstallProcess, siteProcess SitePackagesProcess, sbomGenerator SBOMGenerator, clock chronos.Clock, logger scribe.Emitter) packit.BuildFunc {
	return func(context packit.BuildContext) (packit.BuildResult, error) {
		logger.Title("%s %s", context.BuildpackInfo.Name, context.BuildpackInfo.Version)

		packagesLayer, err := context.Layers.Get(PackagesLayerName)
		if err != nil {
			return packit.BuildResult{}, err
		}

		cacheLayer, err := context.Layers.Get(CacheLayerName)
		if err != nil {
			return packit.BuildResult{}, err
		}

		logger.Process("Executing build process")
		duration, err := clock.Measure(func() error {
			return installProcess.Execute(context.WorkingDir, packagesLayer.Path, cacheLayer.Path)
		})
		if err != nil {
			return packit.BuildResult{}, err
		}

		logger.Action("Completed in %s", duration.Round(time.Millisecond))
		logger.Break()

		planner := draft.NewPlanner()

		packagesLayer.Launch, packagesLayer.Build = planner.MergeLayerTypes(SitePackages, context.Plan.Entries)
		packagesLayer.Cache = packagesLayer.Launch || packagesLayer.Build
		cacheLayer.Cache = true

		sitePackagesPath, err := siteProcess.Execute(packagesLayer.Path)
		if err != nil {
			return packit.BuildResult{}, err
		}

		logger.GeneratingSBOM(packagesLayer.Path)

		var sbomContent sbom.SBOM
		duration, err = clock.Measure(func() error {
			sbomContent, err = sbomGenerator.Generate(context.WorkingDir)
			return err
		})
		if err != nil {
			return packit.BuildResult{}, err
		}
		logger.Action("Completed in %s", duration.Round(time.Millisecond))
		logger.Break()

		logger.FormattingSBOM(context.BuildpackInfo.SBOMFormats...)

		packagesLayer.SBOM, err = sbomContent.InFormats(context.BuildpackInfo.SBOMFormats...)
		if err != nil {
			return packit.BuildResult{}, err
		}

		packagesLayer.SharedEnv.Prepend("PYTHONPATH", sitePackagesPath, string(os.PathListSeparator))

		logger.EnvironmentVariables(packagesLayer)

		layers := []packit.Layer{packagesLayer}
		if _, err := os.Stat(cacheLayer.Path); err == nil {
			if !fs.IsEmptyDir(cacheLayer.Path) {
				layers = append(layers, cacheLayer)
			}
		}

		result := packit.BuildResult{
			Layers: layers,
		}

		return result, nil
	}
}