feat: support detection of node/npm apps

This adds some more logic to also detect node-based frontend apps. The
web-servers buildpack already takes care of running `npm build` but in
case that happens we need to serve the resulting artifacts from
`/workspace/build`. We do that by leveraging the libnodejs package to
detect if we have a nodejs app and then we set the build directory as the
webroot.

detect.go

@@ -1,7 +1,12 @@
 package static
 
 import (
+	"errors"
+	"os"
+	"path/filepath"
+
 	require "github.com/ninech/buildpack-static-require"
+	"github.com/paketo-buildpacks/libnodejs"
 	"github.com/paketo-buildpacks/packit/v2"
 	"github.com/paketo-buildpacks/packit/v2/scribe"
 )
@@ -26,6 +31,14 @@ func Detect(logger scribe.Emitter) packit.DetectFunc {
 			return packit.DetectResult{}, err
 		}
 
+		ok, nodeAppPath, err := isNodeApp(context.WorkingDir)
+		if err != nil {
+			return packit.DetectResult{}, err
+		}
+		if ok {
+			webRoot = filepath.Join(nodeAppPath, "build")
+		}
+
 		result := packit.DetectResult{
 			Plan: packit.BuildPlan{
 				Provides: []packit.BuildPlanProvision{{Name: name}},
@@ -41,3 +54,24 @@ func Detect(logger scribe.Emitter) packit.DetectFunc {
 		return result, nil
 	}
 }
+
+// isNodeApp checks if there is a package.json in the "projectPath". By
+// default that is the workspace but it could also be overridden using
+// BP_NODE_PROJECT_PATH.
+func isNodeApp(workingDir string) (bool, string, error) {
+	projectPath, err := libnodejs.FindProjectPath(workingDir)
+	if err != nil {
+		return false, "", err
+	}
+
+	if _, err := libnodejs.ParsePackageJSON(projectPath); err == nil {
+		relativePath, err := filepath.Rel(workingDir, projectPath)
+		return true, relativePath, err
+	} else {
+		if errors.Is(err, os.ErrNotExist) {
+			return false, "", nil
+		}
+
+		return false, "", err
+	}
+}

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/BurntSushi/toml v1.3.2
 	github.com/ninech/buildpack-static-require v0.0.1
 	github.com/onsi/gomega v1.29.0
+	github.com/paketo-buildpacks/libnodejs v0.2.0
 	github.com/paketo-buildpacks/nginx v0.15.7
 	github.com/paketo-buildpacks/occam v0.17.0
 	github.com/paketo-buildpacks/packit/v2 v2.12.0

go.sum

@@ -2618,6 +2618,8 @@ github.com/otiai10/curr v1.0.0/go.mod h1:LskTG5wDwr8Rs+nNQ+1LlxRjAtTZZjtJW4rMXl6
 github.com/otiai10/mint v1.3.0/go.mod h1:F5AjcsTsWUqX+Na9fpHb52P8pcRX2CI6A3ctIT91xUo=
 github.com/otiai10/mint v1.3.1/go.mod h1:/yxELlJQ0ufhjUwhshSj+wFjZ78CnZ48/1wtmBH1OTc=
 github.com/pact-foundation/pact-go v1.0.4/go.mod h1:uExwJY4kCzNPcHRj+hCR/HBbOOIwwtUjcrb0b5/5kLM=
+github.com/paketo-buildpacks/libnodejs v0.2.0 h1:y7G6BQIeeMUnIlzREiAipQlAcaXJ82VMPldkTTiv9o4=
+github.com/paketo-buildpacks/libnodejs v0.2.0/go.mod h1:JLs6tu5TD6la8p1IKo3UYO1C93/ywGesa74FpM82wPw=
 github.com/paketo-buildpacks/nginx v0.15.7 h1:Pcs7NseRS+8RUL1HY5bkvXNp0NgPV+yDr6Ien97Im4E=
 github.com/paketo-buildpacks/nginx v0.15.7/go.mod h1:Fl+gBf4iFbY18SrmFUfN4K5jXctXOWXK++I5cPu4J1U=
 github.com/paketo-buildpacks/occam v0.17.0 h1:2Xt4Vc4MbSAsLyu+WLttd6gpR4ORsBwcoqAfWz4QaD4=

integration/default_test.go

@@ -101,5 +101,32 @@ func testDefault(t *testing.T, context spec.G, it spec.S) {
 				Eventually(container).Should(Serve(ContainSubstring("satic site served from public dir")).WithEndpoint("/index.html"))
 			})
 		})
+
+		context("when building the react_app", func() {
+			it("serves up the built index.html", func() {
+				var err error
+				source, err = occam.Source(filepath.Join("testdata", "react_app"))
+				Expect(err).NotTo(HaveOccurred())
+
+				var logs fmt.Stringer
+				image, logs, err = pack.WithNoColor().Build.
+					WithPullPolicy("never").
+					WithBuildpacks(
+						buildpack,
+						config.Nginx,
+						config.StaticRequire,
+					).
+					Execute(name, source)
+				Expect(err).NotTo(HaveOccurred(), logs.String())
+
+				container, err = docker.Container.Run.
+					WithEnv(map[string]string{"PORT": "8088"}).
+					WithPublish("8088").
+					Execute(image.ID)
+				Expect(err).ToNot(HaveOccurred())
+
+				Eventually(container).Should(Serve(Not(ContainSubstring("%PUBLIC%"))).WithEndpoint("/index.html"))
+			})
+		})
 	})
 }

integration/testdata/react_app/.gitignore

@@ -0,0 +1,23 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# production
+/build
+
+# misc
+.DS_Store
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*