From fb5a3e35dadebdf0d1fff006461fda271c551b58 Mon Sep 17 00:00:00 2001
From: Ralf Pannemans <ralf.pannemans@sap.com>
Date: Fri, 12 Apr 2024 14:37:48 +0200
Subject: [PATCH] Symlink node_modules/.cache to tempdir

---
 build.go                                | 19 +++++++++++++++++++
 build_test.go                           | 11 +++++++++++
 cmd/setup-symlinks/internal/run.go      |  8 +++++++-
 cmd/setup-symlinks/internal/run_test.go |  1 +
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/build.go b/build.go
index 0b08afb0..d4b8e79f 100644
--- a/build.go
+++ b/build.go
@@ -14,6 +14,8 @@ import (
 	"github.com/paketo-buildpacks/packit/v2/scribe"
 )
 
+const NODE_MODULES_CACHE = "node_modules_cache"
+
 //go:generate faux --interface BuildManager --output fakes/build_manager.go
 type BuildManager interface {
 	Resolve(workingDir string) (BuildProcess, bool, error)
@@ -134,6 +136,23 @@ func Build(entryResolver EntryResolver,
 					return packit.BuildResult{}, err
 				}
 
+				cacheFolder := filepath.Join(os.TempDir(), NODE_MODULES_CACHE)
+				err = os.Mkdir(cacheFolder, os.ModePerm)
+				if err != nil {
+					return packit.BuildResult{}, err
+				}
+
+				linkName := filepath.Join(layer.Path, "node_modules", ".cache")
+				err = os.RemoveAll(linkName)
+				if err != nil {
+					return packit.BuildResult{}, err
+				}
+
+				err = os.Symlink(cacheFolder, linkName)
+				if err != nil {
+					return packit.BuildResult{}, err
+				}
+
 				err = linker.Link(filepath.Join(projectPath, "node_modules"), filepath.Join(layer.Path, "node_modules"))
 				if err != nil {
 					return packit.BuildResult{}, err
diff --git a/build_test.go b/build_test.go
index c6ec01b6..43ef72ff 100644
--- a/build_test.go
+++ b/build_test.go
@@ -60,6 +60,9 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 		cnbDir, err = os.MkdirTemp("", "cnb")
 		Expect(err).NotTo(HaveOccurred())
 
+		tempDir := t.TempDir()
+		t.Setenv("TMPDIR", tempDir)
+
 		t.Setenv("BP_NODE_PROJECT_PATH", "")
 
 		buildProcess = &fakes.BuildProcess{}
@@ -117,6 +120,7 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			environment,
 			symlinkResolver,
 		)
+
 	})
 
 	it.After(func() {
@@ -154,6 +158,13 @@ func testBuild(t *testing.T, context spec.G, it spec.S) {
 			buildLayer := result.Layers[0]
 			Expect(buildLayer.Name).To(Equal("build-modules"))
 			Expect(buildLayer.Path).To(Equal(filepath.Join(layersDir, "build-modules")))
+
+			nodeModuleCache := filepath.Join(layersDir, "build-modules", "node_modules", ".cache")
+			_, err = os.Stat(nodeModuleCache)
+			Expect(err).NotTo(HaveOccurred())
+			// FIXME: Why does this not work?
+			//Expect(info.Mode()&os.ModeSymlink == os.ModeSymlink).To(BeTrue())
+
 			Expect(buildLayer.SharedEnv).To(Equal(packit.Environment{}))
 			Expect(buildLayer.BuildEnv).To(Equal(packit.Environment{
 				"PATH.append":       filepath.Join(layersDir, "build-modules", "node_modules", ".bin"),
diff --git a/cmd/setup-symlinks/internal/run.go b/cmd/setup-symlinks/internal/run.go
index 0099cd9d..3d09f7f7 100644
--- a/cmd/setup-symlinks/internal/run.go
+++ b/cmd/setup-symlinks/internal/run.go
@@ -42,7 +42,13 @@ func Run(executablePath, appDir string, symlinkResolver npminstall.SymlinkResolv
 		return err
 	}
 
-	return createSymlink(filepath.Join(layerPath, "node_modules"), linkPath)
+	err = createSymlink(filepath.Join(layerPath, "node_modules"), linkPath)
+	if err != nil {
+		return err
+	}
+
+	cacheFolder := filepath.Join(os.TempDir(), npminstall.NODE_MODULES_CACHE)
+	return os.Mkdir(cacheFolder, os.ModePerm)
 }
 
 func resolveWorkspaceModules(symlinkResolver npminstall.SymlinkResolver, appDir, layerPath string) error {
diff --git a/cmd/setup-symlinks/internal/run_test.go b/cmd/setup-symlinks/internal/run_test.go
index 40e924ab..d7695979 100644
--- a/cmd/setup-symlinks/internal/run_test.go
+++ b/cmd/setup-symlinks/internal/run_test.go
@@ -41,6 +41,7 @@ func testRun(t *testing.T, context spec.G, it spec.S) {
 
 		tmpDir, err = os.MkdirTemp("", "tmp")
 		Expect(err).NotTo(HaveOccurred())
+		t.Setenv("TMPDIR", tmpDir)
 
 		Expect(os.Symlink(filepath.Join(tmpDir, "node_modules"), filepath.Join(appDir, "node_modules"))).To(Succeed())