move function to find applications into libnodejs

Move function from to find applications from node-start
into libnodejs so that it can be used across buildpacks
and extensions.

API has been refined from what was in node-start to
make it better as a shared function.

Signed-off-by: Michael Dawson <[email protected]>

find_node_application.go

@@ -0,0 +1,46 @@
+package libnodejs
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func FindNodeApplication(workingDir string) (string, error) {
+
+	projectPath, err := FindProjectPath(workingDir)
+	if err != nil {
+		return "", err
+	}
+
+	launchpoint := os.Getenv(LaunchPointEnvName)
+	if launchpoint != "" {
+		if _, err := os.Stat(filepath.Join(workingDir, launchpoint)); err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				return "", fmt.Errorf("expected value derived from BP_LAUNCHPOINT [%s] to be an existing file", launchpoint)
+			}
+
+			return "", err
+		}
+
+		return filepath.Clean(launchpoint), nil
+	}
+
+	files := []string{"server.js", "app.js", "main.js", "index.js"}
+	for _, file := range files {
+		_, err := os.Stat(filepath.Join(projectPath, file))
+		if err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				continue
+			}
+
+			return "", err
+		}
+
+		return filepath.Join(os.Getenv(ProjectPathEnvName), file), nil
+	}
+
+	return "", fmt.Errorf("could not find app in %s: expected one of %s", filepath.Clean(projectPath), strings.Join(files, " | "))
+}

find_node_application_test.go

@@ -0,0 +1,187 @@
+package libnodejs_test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/paketo-buildpacks/libnodejs"
+	"github.com/sclevine/spec"
+
+	. "github.com/onsi/gomega"
+)
+
+func testFindNodeApplication(t *testing.T, context spec.G, it spec.S) {
+	var (
+		Expect = NewWithT(t).Expect
+
+		workingDir string
+	)
+
+	it.Before(func() {
+		workingDir = t.TempDir()
+	})
+
+	it.After(func() {
+		Expect(os.RemoveAll(workingDir)).To(Succeed())
+	})
+
+	context("finds the server.js application entrypoint", func() {
+		it.Before(func() {
+			Expect(os.WriteFile(filepath.Join(workingDir, "server.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "app.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "main.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "index.js"), nil, 0600)).To(Succeed())
+		})
+
+		it("finds the server.js application entrypoint successfully", func() {
+			file, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(file).To(Equal(filepath.Join("server.js")))
+		})
+	})
+
+	context("finds the app.js application entrypoint", func() {
+		it.Before(func() {
+			Expect(os.WriteFile(filepath.Join(workingDir, "app.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "main.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "index.js"), nil, 0600)).To(Succeed())
+		})
+
+		it("finds the app.js application entrypoint successfully", func() {
+			file, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(file).To(Equal(filepath.Join("app.js")))
+		})
+	})
+
+	context("finds the main.js application entrypoint", func() {
+		it.Before(func() {
+			Expect(os.WriteFile(filepath.Join(workingDir, "main.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "index.js"), nil, 0600)).To(Succeed())
+		})
+
+		it("finds the main.js application entrypoint successfully", func() {
+			file, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(file).To(Equal(filepath.Join("main.js")))
+		})
+	})
+
+	context("finds the index.js application entrypoint", func() {
+		it.Before(func() {
+			Expect(os.WriteFile(filepath.Join(workingDir, "index.js"), nil, 0600)).To(Succeed())
+		})
+
+		it("finds the index.js application entrypoint", func() {
+			file, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(file).To(Equal(filepath.Join("index.js")))
+		})
+	})
+
+	context("when there is a launchpoint", func() {
+		it.Before(func() {
+			Expect(os.Mkdir(filepath.Join(workingDir, "src"), os.ModePerm)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "src", "launchpoint.js"), nil, 0600)).To(Succeed())
+		})
+
+		context("when the launchpoint file exists", func() {
+			it("returns the highest priority file", func() {
+				t.Setenv("BP_LAUNCHPOINT", "./src/launchpoint.js")
+				file, err := libnodejs.FindNodeApplication(workingDir)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(file).To(Equal(filepath.Join("src", "launchpoint.js")))
+			})
+		})
+
+		context("when the launchpoint file does not exist", func() {
+			it("returns the empty string and no error", func() {
+				t.Setenv("BP_LAUNCHPOINT", "./no-such-file.js")
+				file, err := libnodejs.FindNodeApplication(workingDir)
+				Expect(err).To(MatchError(ContainSubstring("expected value derived from BP_LAUNCHPOINT [./no-such-file.js] to be an existing file")))
+				Expect(file).To(Equal(""))
+			})
+		})
+	})
+
+	context("when there is a project path", func() {
+		it.Before(func() {
+			Expect(os.Mkdir(filepath.Join(workingDir, "frontend"), os.ModePerm)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "frontend", "server.js"), nil, 0600)).To(Succeed())
+			Expect(os.WriteFile(filepath.Join(workingDir, "frontend", "app.js"), nil, 0600)).To(Succeed())
+		})
+
+		it("returns the highest priority file", func() {
+			t.Setenv("BP_NODE_PROJECT_PATH", "frontend")
+			file, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(file).To(Equal(filepath.Join("frontend", "server.js")))
+		})
+	})
+
+	context("when there is a project path but value specified does not exist", func() {
+		it("returns a failure", func() {
+			t.Setenv("BP_NODE_PROJECT_PATH", "frontend")
+			_, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).To(MatchError(ContainSubstring("no such file or directory")))
+		})
+	})
+
+	context("when no application can be found", func() {
+		it("returns that application could not be found", func() {
+			_, err := libnodejs.FindNodeApplication(workingDir)
+			Expect(err).To(MatchError(fmt.Errorf("could not find app in %s: expected one of server.js | app.js | main.js | index.js", workingDir)))
+		})
+	})
+
+	context("failure cases", func() {
+		context("when the launchpoint cannot be stat'd", func() {
+			it.Before(func() {
+				Expect(os.Chmod(workingDir, 0000)).To(Succeed())
+			})
+
+			it.After(func() {
+				Expect(os.Chmod(workingDir, os.ModePerm)).To(Succeed())
+			})
+
+			it("fails with helpful error", func() {
+				t.Setenv("BP_LAUNCHPOINT", "something.js")
+				_, err := libnodejs.FindNodeApplication(workingDir)
+				Expect(err).To(MatchError(ContainSubstring("permission denied")))
+			})
+		})
+
+		context("when the working dir cannot be stat'd", func() {
+			it.Before(func() {
+				Expect(os.Chmod(workingDir, 0000)).To(Succeed())
+			})
+
+			it.After(func() {
+				Expect(os.Chmod(workingDir, os.ModePerm)).To(Succeed())
+			})
+
+			it("fails with helpful error", func() {
+				_, err := libnodejs.FindNodeApplication(workingDir)
+				Expect(err).To(MatchError(ContainSubstring("permission denied")))
+			})
+		})
+
+		context("when the project path cannot be stat'd", func() {
+			it.Before(func() {
+				Expect(os.Chmod(workingDir, 0000)).To(Succeed())
+			})
+
+			it.After(func() {
+				Expect(os.Chmod(workingDir, os.ModePerm)).To(Succeed())
+			})
+
+			it("fails with helpful error", func() {
+				t.Setenv("BP_NODE_PROJECT_PATH", "frontend")
+				_, err := libnodejs.FindNodeApplication(workingDir)
+				Expect(err).To(MatchError(ContainSubstring("permission denied")))
+			})
+		})
+	})
+}

init_test.go

@@ -11,5 +11,6 @@ func TestUnitLibnodejs(t *testing.T) {
 	suite := spec.New("libnodejs", spec.Report(report.Terminal{}), spec.Sequential())
 	suite("FindProjectPath", testFindProjectPath)
 	suite("PackageJSON", testPackageJSON)
+	suite("FindNodeApplication", testFindNodeApplication)
 	suite.Run(t)
 }

spec_constants.go

@@ -1,3 +1,4 @@
 package libnodejs
 
 const ProjectPathEnvName = "BP_NODE_PROJECT_PATH"
+const LaunchPointEnvName = "BP_LAUNCHPOINT"