Create intermediate symlink for switching between build and launch mo…

…dules

build.go

@@ -48,7 +48,9 @@ func Build(projectPathParser PathParser,
 	pruneProcess PruneProcess,
 	clock chronos.Clock,
 	logger scribe.Emitter,
-	sbomGenerator SBOMGenerator) packit.BuildFunc {
+	sbomGenerator SBOMGenerator,
+	tmpDir string,
+) packit.BuildFunc {
 	return func(context packit.BuildContext) (packit.BuildResult, error) {
 		logger.Title("%s %s", context.BuildpackInfo.Name, context.BuildpackInfo.Version)
 
@@ -219,11 +221,17 @@ func Build(projectPathParser PathParser,
 						return packit.BuildResult{}, err
 					}
 
-					err = os.Symlink(filepath.Join(buildLayerPath, "node_modules"), filepath.Join(projectPath, "node_modules"))
+					err = os.Symlink(filepath.Join(buildLayerPath, "node_modules"), filepath.Join(tmpDir, "node_modules"))
 					if err != nil {
 						return packit.BuildResult{}, err
 					}
 
+					err = os.Symlink(filepath.Join(tmpDir, "node_modules"), filepath.Join(projectPath, "node_modules"))
+					if err != nil {
+						return packit.BuildResult{}, err
+					}
+
+					layer.ExecD = []string{filepath.Join(context.CNBPath, "bin", "setup-symlinks")}
 				}
 
 				logger.Action("Completed in %s", duration.Round(time.Millisecond))
@@ -264,7 +272,6 @@ func Build(projectPathParser PathParser,
 					}
 				}
 
-				layer.ExecD = []string{filepath.Join(context.CNBPath, "bin", "setup-symlinks")}
 			} else {
 				logger.Process("Reusing cached layer %s", layer.Path)
 				if !build {
@@ -295,14 +302,6 @@ func Build(projectPathParser PathParser,
 			return packit.BuildResult{}, err
 		}
 
-		// Makes the projectPath group-writable to facilitate executing exec.d
-		// script at runtime under a different uid.
-		// https://github.com/paketo-buildpacks/rfcs/blob/main/text/0045-user-ids.md
-		err = os.Chmod(projectPath, 0775)
-		if err != nil {
-			return packit.BuildResult{}, err
-		}
-
 		logger.Break()
 
 		return packit.BuildResult{Layers: layers}, nil

build_test.go

@@ -24,6 +24,7 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 		Expect = NewWithT(t).Expect
 
 		layersDir  string
+		tmpDir     string
 		workingDir string
 		cnbDir     string
 
@@ -49,6 +50,9 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 		layersDir, err = os.MkdirTemp("", "layers")
 		Expect(err).NotTo(HaveOccurred())
 
+		tmpDir, err = os.MkdirTemp("", "tmp")
+		Expect(err).NotTo(HaveOccurred())
+
 		workingDir, err = os.MkdirTemp("", "working-dir")
 		Expect(err).NotTo(HaveOccurred())
 
@@ -103,11 +107,13 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			chronos.DefaultClock,
 			logger,
 			sbomGenerator,
+			tmpDir,
 		)
 	})
 
 	it.After(func() {
 		Expect(os.RemoveAll(layersDir)).To(Succeed())
+		Expect(os.RemoveAll(tmpDir)).To(Succeed())
 		Expect(os.RemoveAll(workingDir)).To(Succeed())
 	})
 
@@ -193,10 +199,6 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			Expect(processWorkingDir).To(Equal(workingDir))
 			Expect(processNpmrcPath).To(Equal(""))
 
-			workingDirInfo, err := os.Stat(workingDir)
-			Expect(err).NotTo(HaveOccurred())
-			Expect(workingDirInfo.Mode()).To(Equal(os.FileMode(os.ModeDir | 0775)))
-
 		})
 	})
 
@@ -243,9 +245,6 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 				map[string]interface{}{
 					"cache_sha": "some-sha",
 				}))
-			Expect(launchLayer.ExecD).To(Equal([]string{
-				filepath.Join(cnbDir, "bin", "setup-symlinks"),
-			}))
 
 			Expect(launchLayer.SBOM.Formats()).To(Equal([]packit.SBOMFormat{
 				{
@@ -370,6 +369,9 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 				map[string]interface{}{
 					"cache_sha": "some-sha",
 				}))
+			Expect(launchLayer.ExecD).To(Equal([]string{
+				filepath.Join(cnbDir, "bin", "setup-symlinks"),
+			}))
 
 			Expect(launchLayer.SBOM.Formats()).To(Equal([]packit.SBOMFormat{
 				{
@@ -401,6 +403,15 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			Expect(pruneProcess.RunCall.Receives.CacheDir).To(Equal(cacheLayer.Path))
 			Expect(pruneProcess.RunCall.Receives.WorkingDir).To(Equal(workingDir))
 			Expect(pruneProcess.RunCall.Receives.NpmrcPath).To(Equal(""))
+
+			link, err := os.Readlink(filepath.Join(tmpDir, "node_modules"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(link).To(Equal(filepath.Join(buildLayer.Path, "node_modules")))
+
+			link, err = os.Readlink(filepath.Join(workingDir, "node_modules"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(link).To(Equal(filepath.Join(tmpDir, "node_modules")))
+
 		})
 	})
 
@@ -514,9 +525,6 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 				Expect(processCacheDir).To(Equal(filepath.Join(layersDir, npminstall.LayerNameCache)))
 				Expect(processWorkingDir).To(Equal(filepath.Join(workingDir, "some-dir")))
 
-				procWorkingDirInfo, err := os.Stat(processWorkingDir)
-				Expect(err).NotTo(HaveOccurred())
-				Expect(procWorkingDirInfo.Mode()).To(Equal(os.FileMode(os.ModeDir | 0775)))
 			})
 		})
 

cmd/setup-symlinks/internal/run.go

@@ -7,19 +7,14 @@ import (
 	"strings"
 )
 
-func Run(executablePath, appDir string) error {
+func Run(executablePath, appDir, tmpDir string) error {
 	fname := strings.Split(executablePath, "/")
 	layerPath := filepath.Join(fname[:len(fname)-2]...)
 	if filepath.IsAbs(executablePath) {
 		layerPath = fmt.Sprintf("/%s", layerPath)
 	}
 
-	err := os.RemoveAll(filepath.Join(appDir, "node_modules"))
-	if err != nil {
-		return err
-	}
-
-	err = os.Symlink(filepath.Join(layerPath, "node_modules"), filepath.Join(appDir, "node_modules"))
+	err := os.Symlink(filepath.Join(layerPath, "node_modules"), filepath.Join(tmpDir, "node_modules"))
 	if err != nil {
 		return err
 	}

cmd/setup-symlinks/internal/run_test.go

@@ -25,6 +25,7 @@ func testRun(t *testing.T, context spec.G, it spec.S) {
 		layerDir       string
 		executablePath string
 		appDir         string
+		tmpDir         string
 	)
 
 	it.Before(func() {
@@ -35,6 +36,9 @@ func testRun(t *testing.T, context spec.G, it spec.S) {
 		appDir, err = os.MkdirTemp("", "appDir")
 		Expect(err).NotTo(HaveOccurred())
 
+		tmpDir, err = os.MkdirTemp("", "tmp")
+		Expect(err).NotTo(HaveOccurred())
+
 		Expect(os.MkdirAll(filepath.Join(layerDir, "node_modules"), os.ModePerm)).To(Succeed())
 
 		executablePath = filepath.Join(layerDir, "execd", "0-setup-symlinks")
@@ -43,8 +47,6 @@ func testRun(t *testing.T, context spec.G, it spec.S) {
 		err = os.WriteFile(executablePath, []byte(""), 0600)
 		Expect(err).NotTo(HaveOccurred())
 
-		Expect(os.Symlink("build-modules", filepath.Join(appDir, "node_modules"))).To(Succeed())
-
 	})
 
 	it.After(func() {
@@ -53,24 +55,24 @@ func testRun(t *testing.T, context spec.G, it spec.S) {
 	})
 
 	it("creates a symlink to the node_modules dir in the layer", func() {
-		err := internal.Run(executablePath, appDir)
+		err := internal.Run(executablePath, appDir, tmpDir)
 		Expect(err).NotTo(HaveOccurred())
 
-		link, err := os.Readlink(filepath.Join(appDir, "node_modules"))
+		link, err := os.Readlink(filepath.Join(tmpDir, "node_modules"))
 		Expect(err).NotTo(HaveOccurred())
 		Expect(link).To(Equal(filepath.Join(layerDir, "node_modules")))
 	})
 
 	context("failure cases", func() {
-		context("when the app dir node_modules cannot be removed", func() {
+		context("when the tmp dir node_modules cannot be removed", func() {
 			it.Before(func() {
-				Expect(os.Chmod(appDir, 0444)).To(Succeed())
+				Expect(os.Chmod(tmpDir, 0444)).To(Succeed())
 			})
 			it.After(func() {
-				Expect(os.Chmod(appDir, os.ModePerm)).To(Succeed())
+				Expect(os.Chmod(tmpDir, os.ModePerm)).To(Succeed())
 			})
 			it("returns an error", func() {
-				err := internal.Run(executablePath, appDir)
+				err := internal.Run(executablePath, appDir, tmpDir)
 				Expect(err).To(MatchError(ContainSubstring("permission denied")))
 			})
 		})

cmd/setup-symlinks/main.go

@@ -13,7 +13,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	err = internal.Run(os.Args[0], wd)
+	err = internal.Run(os.Args[0], wd, "/tmp")
 	if err != nil {
 		log.Fatal(err)
 	}

run/main.go

@@ -31,6 +31,7 @@ func main() {
 	entryResolver := draft.NewPlanner()
 	sbomGenerator := SBOMGenerator{}
 	packageManagerConfigurationManager := npminstall.NewPackageManagerConfigurationManager(servicebindings.NewResolver(), logger)
+	tmpDir := "/tmp"
 
 	packit.Run(
 		npminstall.Detect(
@@ -45,6 +46,8 @@ func main() {
 			pruneBuildProcess,
 			chronos.DefaultClock,
 			logger,
-			sbomGenerator),
+			sbomGenerator,
+			tmpDir,
+		),
 	)
 }