more robust entry point logic for nodejs

Currently we set the default entry point for nodejs applications to `npm run start` even if the package.json does not define a start script. This commit updates the logic to use fall back to either the "main" script from the package.json or use `node index.js` if neither is available. fixes #375 PiperOrigin-RevId: 602032240 Change-Id: I9776c9f2f4dca514fb0f3c9dc6ba93ef4ab375bb
GoogleCloudPlatform · Jan 27, 2024 · f6258a2 · f6258a2 · steren · Jan 27, 2024
1 parent 189dfb9
commit f6258a2
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Showing 5 changed files with 114 additions and 3 deletions.
diff --git a/cmd/nodejs/npm/main.go b/cmd/nodejs/npm/main.go
@@ -174,7 +174,10 @@ NOTE: Running the default build script can be skipped by passing the empty envir
 	el.SharedEnvironment.Default("NODE_ENV", nodejs.NodeEnv())
 
 	// Configure the entrypoint for production.
-	cmd := []string{"npm", "start"}
+	cmd, err := nodejs.DefaultStartCommand(ctx, pjs)
+	if err != nil {
+		return fmt.Errorf("detecting start command: %w", err)
+	}
 
 	if !devmode.Enabled(ctx) {
 		ctx.AddWebProcess(cmd)

diff --git a/pkg/nodejs/BUILD.bazel b/pkg/nodejs/BUILD.bazel
@@ -46,6 +46,7 @@ go_test(
     embed = [":nodejs"],
     rundir = ".",
     deps = [
+        "//security/safeopen",
         "//internal/mockprocess",
         "//internal/testserver",
         "//pkg/env",

diff --git a/pkg/nodejs/nodejs.go b/pkg/nodejs/nodejs.go
@@ -61,8 +61,6 @@ type packageEnginesJSON struct {
 const (
 	// ScriptBuild is the name of npm build scripts.
 	ScriptBuild = "build"
-	// ScriptStart is the name of npm start scripts.
-	ScriptStart = "start"
 	// ScriptGCPBuild is the name of "gcp-build" scripts.
 	ScriptGCPBuild = "gcp-build"
 )

diff --git a/pkg/nodejs/npm.go b/pkg/nodejs/npm.go
@@ -197,3 +197,30 @@ func IsUsingVendoredDependencies() bool {
 func runCommand(pkgTool, command string) string {
 	return fmt.Sprintf("%s run %s", pkgTool, strings.TrimSpace(command))
 }
+
+// DefaultStartCommand return the default command that should be used to configure the application
+// web process if the user has not explicitly configured one. The algorithm follows the conventions
+// of Nodejs package.json files: https://docs.npmjs.com/cli/v10/configuring-npm/package-json#main
+// 1. if script.start is specified return `npm run start`
+// 2. if the project contains server.js `npm run start`
+// 3. if main is specified `node ${pjs.main}`
+// 4. otherwise `node index.js“
+func DefaultStartCommand(ctx *gcp.Context, pjs *PackageJSON) ([]string, error) {
+	if pjs == nil {
+		return []string{"node", "index.js"}, nil
+	}
+	if _, ok := pjs.Scripts["start"]; ok {
+		return []string{"npm", "run", "start"}, nil
+	}
+	exists, err := ctx.FileExists(ctx.ApplicationRoot(), "server.js")
+	if err != nil {
+		return nil, err
+	}
+	if exists {
+		return []string{"npm", "run", "start"}, nil
+	}
+	if pjs.Main != "" {
+		return []string{"node", pjs.Main}, nil
+	}
+	return []string{"node", "index.js"}, nil
+}
diff --git a/pkg/nodejs/npm_test.go b/pkg/nodejs/npm_test.go
@@ -18,6 +18,7 @@ import (
 	"encoding/json"
 	"testing"
 
+	"google3/security/safeopen/safeopen"
 	"github.com/GoogleCloudPlatform/buildpacks/pkg/env"
 	"github.com/GoogleCloudPlatform/buildpacks/pkg/gcpbuildpack"
 	"github.com/google/go-cmp/cmp"
@@ -330,3 +331,84 @@ func TestDetermineBuildCommands(t *testing.T) {
 		})
 	}
 }
+
+func TestDefaultStartCommand(t *testing.T) {
+	testsCases := []struct {
+		name        string
+		pjs         string
+		hasServerJs bool
+		want        []string
+	}{
+		{
+			name: "no package.json",
+			want: []string{"node", "index.js"},
+		},
+		{
+			name: "no main or start",
+			pjs: `{
+				"scripts": {
+					"build": "tsc --build",
+					"clean": "tsc --build --clean"
+				}
+			}`,
+			want: []string{"node", "index.js"},
+		},
+		{
+			name: "main and start uses start",
+			pjs: `{
+				"main": "main.js",
+				"scripts": {
+					"start": "node main.js"
+				}
+			}`,
+			want: []string{"npm", "run", "start"},
+		},
+		{
+			name: "main module",
+			pjs: `{
+				"main": "main.js",
+				"scripts": {
+					"build": "node main.js"
+				}
+			}`,
+			want: []string{"node", "main.js"},
+		},
+		{
+			name: "main module and serverjs",
+			pjs: `{
+				"main": "main.js",
+				"scripts": {
+					"build": "node main.js"
+				}
+			}`,
+			hasServerJs: true,
+			want:        []string{"npm", "run", "start"},
+		},
+	}
+	for _, tc := range testsCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var pjs *PackageJSON = nil
+			if tc.pjs != "" {
+				if err := json.Unmarshal([]byte(tc.pjs), &pjs); err != nil {
+					t.Fatalf("failed to unmarshal package.json: %s, error: %v", tc.pjs, err)
+				}
+			}
+			home := t.TempDir()
+			if tc.hasServerJs {
+				_, err := safeopen.CreateBeneath(home, "server.js")
+				if err != nil {
+					t.Fatalf("failed to create server.js: %v", err)
+				}
+			}
+			ctx := gcpbuildpack.NewContext(gcpbuildpack.WithApplicationRoot(home))
+
+			got, err := DefaultStartCommand(ctx, pjs)
+			if err != nil {
+				t.Fatalf("DefaultStartCommand() got error: %v", err)
+			}
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Errorf("DefaultStartCommand() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}