Fix cyclic symlink on rebuild when filesystem caching is enabled (pak…

…eto-buildpacks#408)

* Checks for existing node_modules symlink

* Fix unit tests; use Lstat instead of Readlink

* Fix integration tests; create symlink when only launch_modules required

build.go

@@ -115,7 +115,7 @@ func Build(pathParser PathParser,
 					return packit.BuildResult{}, err
 				}
 
-				currentModLayer, err = installProcess.SetupModules(context.WorkingDir, currentModLayer, layer.Path)
+				currentModLayer, err = installProcess.SetupModules(projectPath, currentModLayer, layer.Path)
 				if err != nil {
 					return packit.BuildResult{}, err
 				}
@@ -206,7 +206,7 @@ func Build(pathParser PathParser,
 					return packit.BuildResult{}, err
 				}
 
-				_, err = installProcess.SetupModules(context.WorkingDir, currentModLayer, layer.Path)
+				_, err = installProcess.SetupModules(projectPath, currentModLayer, layer.Path)
 				if err != nil {
 					return packit.BuildResult{}, err
 				}
@@ -221,6 +221,13 @@ func Build(pathParser PathParser,
 				logger.Action("Completed in %s", duration.Round(time.Millisecond))
 				logger.Break()
 
+				if !build {
+					err = ensureNodeModulesSymlink(projectPath, layer.Path, tmpDir)
+					if err != nil {
+						return packit.BuildResult{}, err
+					}
+				}
+
 				layer.Metadata = map[string]interface{}{
 					"cache_sha": sha,
 				}
@@ -256,10 +263,7 @@ func Build(pathParser PathParser,
 				}
 
 				layer.ExecD = []string{filepath.Join(context.CNBPath, "bin", "setup-symlinks")}
-				err = ensureNodeModulesSymlink(projectPath, layer.Path, tmpDir)
-				if err != nil {
-					return packit.BuildResult{}, err
-				}
+
 			} else {
 				logger.Process("Reusing cached layer %s", layer.Path)
 				if !build {
@@ -273,6 +277,7 @@ func Build(pathParser PathParser,
 			layer.Launch = true
 
 			layers = append(layers, layer)
+
 		}
 
 		err = symlinker.Unlink(filepath.Join(homeDir, ".npmrc"))

build_test.go

@@ -211,7 +211,7 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 
 			Expect(installProcess.ShouldRunCall.Receives.WorkingDir).To(Equal(filepath.Join(workingDir, "some-project-dir")))
 
-			Expect(installProcess.SetupModulesCall.Receives.WorkingDir).To(Equal(workingDir))
+			Expect(installProcess.SetupModulesCall.Receives.WorkingDir).To(Equal(filepath.Join(workingDir, "some-project-dir")))
 			Expect(installProcess.SetupModulesCall.Receives.CurrentModulesLayerPath).To(Equal(""))
 			Expect(installProcess.SetupModulesCall.Receives.NextModulesLayerPath).To(Equal(layer.Path))
 
@@ -265,6 +265,7 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 				"PATH.delim":                ":",
 			}))
 			Expect(layer.Launch).To(BeTrue())
+			Expect(layer.Build).To(BeFalse())
 			Expect(layer.Metadata).To(Equal(
 				map[string]interface{}{
 					"cache_sha": "some-awesome-shasum",
@@ -300,7 +301,7 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 
 			Expect(installProcess.ShouldRunCall.Receives.WorkingDir).To(Equal(filepath.Join(workingDir, "some-project-dir")))
 
-			Expect(installProcess.SetupModulesCall.Receives.WorkingDir).To(Equal(workingDir))
+			Expect(installProcess.SetupModulesCall.Receives.WorkingDir).To(Equal(filepath.Join(workingDir, "some-project-dir")))
 			Expect(installProcess.SetupModulesCall.Receives.CurrentModulesLayerPath).To(Equal(""))
 			Expect(installProcess.SetupModulesCall.Receives.NextModulesLayerPath).To(Equal(layer.Path))
 
@@ -309,6 +310,14 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			Expect(installProcess.ExecuteCall.Receives.Launch).To(BeTrue())
 
 			Expect(sbomGenerator.GenerateCall.Receives.Dir).To(Equal(workingDir))
+
+			workspaceLink, err := os.Readlink(filepath.Join(workingDir, "some-project-dir", "node_modules"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(workspaceLink).To(Equal(filepath.Join(tmpDir, "node_modules")))
+
+			tmpLink, err := os.Readlink(filepath.Join(tmpDir, "node_modules"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(tmpLink).To(Equal(filepath.Join(layersDir, "launch-modules", "node_modules")))
 		})
 	})
 
@@ -356,6 +365,7 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 		it.Before(func() {
 			entryResolver.MergeLayerTypesCall.Returns.Launch = true
 			entryResolver.MergeLayerTypesCall.Returns.Build = true
+			pathParser.GetCall.Returns.ProjectPath = workingDir
 
 			installProcess.SetupModulesCall.Stub = func(w string, c string, n string) (string, error) {
 				setupModulesCalls = append(setupModulesCalls, setupModulesParams{
@@ -406,6 +416,14 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			Expect(setupModulesCalls[1].WorkingDir).To(Equal(workingDir))
 			Expect(setupModulesCalls[1].CurrentModulesLayerPath).To(Equal(result.Layers[0].Path))
 			Expect(setupModulesCalls[1].NextModulesLayerPath).To(Equal(result.Layers[1].Path))
+
+			workspaceLink, err := os.Readlink(filepath.Join(workingDir, "node_modules"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(workspaceLink).To(Equal(filepath.Join(tmpDir, "node_modules")))
+
+			tmpLink, err := os.Readlink(filepath.Join(tmpDir, "node_modules"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(tmpLink).To(Equal(filepath.Join(layersDir, "build-modules", "node_modules")))
 		})
 	})
 

install_process.go

@@ -99,8 +99,26 @@ func (ip YarnInstallProcess) SetupModules(workingDir, currentModulesLayerPath, n
 		}
 
 	} else {
-		err := os.MkdirAll(filepath.Join(workingDir, "node_modules"), os.ModePerm)
+
+		file, err := os.Lstat(filepath.Join(workingDir, "node_modules"))
+		if err != nil {
+			if !errors.Is(err, os.ErrNotExist) {
+				return "", fmt.Errorf("failed to stat node_modules directory: %w", err)
+			}
+
+		}
+
+		if file != nil && file.Mode()&os.ModeSymlink == os.ModeSymlink {
+			err = os.RemoveAll(filepath.Join(workingDir, "node_modules"))
+			if err != nil {
+				//not tested
+				return "", fmt.Errorf("failed to remove node_modules symlink: %w", err)
+			}
+		}
+
+		err = os.MkdirAll(filepath.Join(workingDir, "node_modules"), os.ModePerm)
 		if err != nil {
+			//not directly tested
 			return "", fmt.Errorf("failed to create node_modules directory: %w", err)
 		}
 

install_process_test.go

@@ -256,7 +256,7 @@ func testInstallProcess(t *testing.T, context spec.G, it spec.S) {
 				})
 			})
 
-			context("node_modules directory cannot be created in working directory", func() {
+			context("Lstat() cannot be run on node_modules in working directory", func() {
 				it.Before(func() {
 					Expect(os.Chmod(workingDir, 0000)).To(Succeed())
 				})
@@ -267,7 +267,7 @@ func testInstallProcess(t *testing.T, context spec.G, it spec.S) {
 
 				it("returns an error", func() {
 					_, err := installProcess.SetupModules(workingDir, "", nextModulesLayerPath)
-					Expect(err).To(MatchError(ContainSubstring("failed to create node_modules directory:")))
+					Expect(err).To(MatchError(ContainSubstring("failed to stat node_modules directory:")))
 					Expect(err).To(MatchError(ContainSubstring("permission denied")))
 				})
 			})