feat: add opt-in to use this buildpack for all package managers (#171)

This will allow, in tandem with python-package-managers-run
and python-start, to request the use of
python-package-managers-install in place of the other set of
buildpacks.

Author: sgaist

README.md

@@ -32,6 +32,22 @@ The buildpack will do the following:
 * At run time:
   - Does nothing
 
+## Configuration
+
+### `BP_ENABLE_PACKAGE_MANAGERS`
+
+The `BP_ENABLE_PACKAGE_MANAGERS` environment variable allows you to force the use
+of this buildpack for all the supported package managers. It works in tandem
+with `python-start`. `python-start` will add a requirement that is fulfilled by
+this buildpack.
+
+It is currently used as an opt-in to allow Paketo users to do tests before the
+old buildpacks get retired.
+
+```shell
+BP_ENABLE_PACKAGE_MANAGERS=true
+```
+
 ## Usage
 
 To package this buildpack for consumption:

constants.go

@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: © 2026 Idiap Research Institute <contact@idiap.ch>
+// SPDX-FileContributor: Samuel Gaist <samuel.gaist@idiap.ch>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package pythoninstallers
+
+const (
+	PackageManagersEnv              = "BP_ENABLE_PACKAGE_MANAGERS"
+	PackageManagersInstallPlanEntry = "package-managers-install"
+)

detect.go

@@ -6,6 +6,10 @@
 package pythoninstallers
 
 import (
+	"fmt"
+	"os"
+	"strconv"
+
 	"github.com/paketo-buildpacks/packit/v2"
 	"github.com/paketo-buildpacks/packit/v2/scribe"
 
@@ -78,6 +82,23 @@ func Detect(logger scribe.Emitter, pyProjectParser poetry.PyProjectParser) packi
 			return packit.DetectResult{}, packit.Fail.WithMessage("No python packager manager related files found")
 		}
 
+		shouldUsePackageManagers := false
+
+		if usePackageManagers, ok := os.LookupEnv(PackageManagersEnv); ok {
+			shouldUsePackageManagers, err = strconv.ParseBool(usePackageManagers)
+			if err != nil {
+				return packit.DetectResult{}, fmt.Errorf("failed to parse %s value %s: %w", PackageManagersEnv, usePackageManagers, err)
+			}
+		}
+
+		if shouldUsePackageManagers {
+			for i, plan := range plans {
+				plans[i].Provides = append(plan.Provides, packit.BuildPlanProvision{
+					Name: PackageManagersInstallPlanEntry,
+				})
+			}
+		}
+
 		return packit.DetectResult{
 			Plan: Or(plans...),
 		}, nil

detect_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/sclevine/spec"
 
 	. "github.com/onsi/gomega"
+	"github.com/onsi/gomega/gstruct"
 )
 
 func testDetect(t *testing.T, context spec.G, it spec.S) {
@@ -274,5 +275,25 @@ func testDetect(t *testing.T, context spec.G, it spec.S) {
 				Expect(result.Plan).To(Equal(pythoninstallers.Or(withUv...)))
 			})
 		})
+
+		context("When BP_ENABLE_PACKAGE_MANAGERS is set", func() {
+			it.Before(func() {
+				t.Setenv("BP_ENABLE_PACKAGE_MANAGERS", "true")
+				Expect(os.WriteFile(filepath.Join(workingDir, "environment.yml"), []byte{}, os.ModePerm)).To(Succeed())
+			})
+
+			it("passes detection", func() {
+				result, err := detect(packit.DetectContext{
+					WorkingDir: workingDir,
+				})
+				Expect(err).NotTo(HaveOccurred())
+				Expect(result.Plan.Provides).To(ContainElement(
+					gstruct.MatchAllFields(gstruct.Fields{
+						"Name": Equal(pythoninstallers.PackageManagersInstallPlanEntry),
+					}),
+				))
+			})
+		})
+
 	})
 }

integration/installers/init_test.go

@@ -120,5 +120,8 @@ func TestIntegration(t *testing.T) {
 	suite("pixi LayerReuse", pixiTestLayerReuse, spec.Parallel())
 	suite("pixi Offline", pixiTestOffline, spec.Parallel())
 
+	// Make package-managers mandatory
+	suite("mandatory package managers", pmTestMandatory)
+
 	suite.Run(t)
 }

integration/installers/pm_mandatory_test.go

@@ -0,0 +1,120 @@
+// SPDX-FileCopyrightText: Copyright (c) 2013-Present CloudFoundry.org Foundation, Inc. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package integration_test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/paketo-buildpacks/occam"
+	"github.com/sclevine/spec"
+
+	. "github.com/onsi/gomega"
+)
+
+func pmTestMandatory(t *testing.T, context spec.G, it spec.S) {
+	var (
+		Expect     = NewWithT(t).Expect
+		Eventually = NewWithT(t).Eventually
+		pack       occam.Pack
+		docker     occam.Docker
+	)
+
+	it.Before(func() {
+		pack = occam.NewPack()
+		docker = occam.NewDocker()
+	})
+
+	context("when building a prepared app", func() {
+		var (
+			image     occam.Image
+			container occam.Container
+			name      string
+			source    string
+		)
+
+		it.Before(func() {
+			var err error
+			name, err = occam.RandomName()
+			Expect(err).NotTo(HaveOccurred())
+
+			source, err = occam.Source(filepath.Join("testdata", "conda", "pm_mandatory_app"))
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		it.After(func() {
+			Expect(docker.Container.Remove.Execute(container.ID)).To(Succeed())
+			Expect(docker.Image.Remove.Execute(image.ID)).To(Succeed())
+			Expect(docker.Volume.Remove.Execute(occam.CacheVolumeNames(name))).To(Succeed())
+			Expect(os.RemoveAll(source)).To(Succeed())
+		})
+
+		it("builds an oci image that has the correct behavior", func() {
+			var err error
+
+			var logs fmt.Stringer
+			image, logs, err = pack.WithNoColor().Build.
+				WithPullPolicy("never").
+				WithBuildpacks(
+					settings.Buildpacks.PythonInstallers.Online,
+					settings.Buildpacks.BuildPlan.Online,
+				).
+				WithEnv(map[string]string{
+					"BP_ENABLE_PACKAGE_MANAGERS": "true",
+				}).
+				Execute(name, source)
+			Expect(err).NotTo(HaveOccurred(), logs.String())
+
+			container, err = docker.Container.Run.
+				WithCommand("conda info").
+				WithPublish("8080").
+				WithPublishAll().
+				Execute(image.ID)
+			Expect(err).NotTo(HaveOccurred())
+
+			Eventually(func() string {
+				cLogs, err := docker.Container.Logs.Execute(container.ID)
+				Expect(err).NotTo(HaveOccurred())
+				return cLogs.String()
+			}).Should(MatchRegexp(`conda version : \d+\.\d+\.\d+`))
+		})
+	})
+
+	context("when building a default app", func() {
+		var (
+			name   string
+			source string
+		)
+
+		it.Before(func() {
+			var err error
+			name, err = occam.RandomName()
+			Expect(err).NotTo(HaveOccurred())
+
+			source, err = occam.Source(filepath.Join("testdata", "conda", "miniconda_app"))
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		it("fails to build an oci image", func() {
+			var err error
+
+			var logs fmt.Stringer
+			_, logs, err = pack.WithNoColor().Build.
+				WithPullPolicy("never").
+				WithBuildpacks(
+					settings.Buildpacks.PythonInstallers.Online,
+					settings.Buildpacks.BuildPlan.Online,
+				).
+				WithEnv(map[string]string{
+					"BP_ENABLE_PACKAGE_MANAGERS": "true",
+				}).
+				Execute(name, source)
+			Expect(err).To(HaveOccurred(), logs.String())
+		})
+
+	})
+}

integration/installers/testdata/conda/pm_mandatory_app/plan.toml

@@ -0,0 +1,12 @@
+# Copyright (c) 2013-Present CloudFoundry.org Foundation, Inc. All Rights Reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+[[requires]]
+  name = "conda"
+
+[requires.metadata]
+  launch = true
+
+[[requires]]
+name = "package-managers-install"