Fix vendored Yarn deployments calling yarn install instead of yarn rebuild

src/nodejs/supply/supply.go

@@ -46,6 +46,7 @@ type NPM interface {
 
 type Yarn interface {
 	Build(buildDir, cacheDir string, isBerry bool) error
+	Rebuild(buildDir string) error
 }
 
 type PNPM interface {
@@ -340,6 +341,12 @@ func (s *Supplier) BuildDependencies() error {
 	}
 
 	switch {
+	case s.UseYarn && s.IsVendored:
+		s.Log.Info("Prebuild detected (node_modules already exists)")
+		if err := s.Yarn.Rebuild(s.Stager.BuildDir()); err != nil {
+			return err
+		}
+
 	case s.UseYarn:
 		if err := s.Yarn.Build(s.Stager.BuildDir(), s.Stager.CacheDir(), s.UsesYarnBerry); err != nil {
 			return err

src/nodejs/supply/supply_test.go

@@ -1201,6 +1201,35 @@ var _ = Describe("Supply", func() {
 			})
 		})
 
+		Context("using yarn with vendored node_modules", func() {
+			BeforeEach(func() {
+				supplier.UseYarn = true
+				supplier.IsVendored = true
+			})
+
+			It("runs yarn rebuild instead of yarn build", func() {
+				mockYarn.EXPECT().Rebuild(buildDir).Return(nil)
+				Expect(supplier.BuildDependencies()).To(Succeed())
+				Expect(buffer.String()).To(ContainSubstring("Prebuild detected (node_modules already exists)"))
+			})
+
+			It("runs prebuild script when specified", func() {
+				supplier.PreBuild = "prescriptive"
+				mockYarn.EXPECT().Rebuild(buildDir).Return(nil)
+				mockCommand.EXPECT().Execute(buildDir, gomock.Any(), gomock.Any(), "yarn", "run", "heroku-prebuild")
+				Expect(supplier.BuildDependencies()).To(Succeed())
+				Expect(buffer.String()).To(ContainSubstring("Running heroku-prebuild (yarn)"))
+			})
+
+			It("runs postbuild script when specified", func() {
+				supplier.PostBuild = "descriptive"
+				mockYarn.EXPECT().Rebuild(buildDir).Return(nil)
+				mockCommand.EXPECT().Execute(buildDir, gomock.Any(), gomock.Any(), "yarn", "run", "heroku-postbuild")
+				Expect(supplier.BuildDependencies()).To(Succeed())
+				Expect(buffer.String()).To(ContainSubstring("Running heroku-postbuild (yarn)"))
+			})
+		})
+
 		Describe("using npm", func() {
 			BeforeEach(func() {
 				supplier.UseYarn = false

src/nodejs/yarn/yarn.go

@@ -99,3 +99,13 @@ func (y *Yarn) buildClassic(buildDir, cacheDir string) error {
 
 	return nil
 }
+
+func (y *Yarn) Rebuild(buildDir string) error {
+	y.Log.Info("Rebuilding any native modules (yarn)")
+	cmd := exec.Command("yarn", "rebuild")
+	cmd.Dir = buildDir
+	cmd.Stdout = y.Log.Output()
+	cmd.Stderr = y.Log.Output()
+	cmd.Env = append(os.Environ(), "npm_config_nodedir="+os.Getenv("NODE_HOME"))
+	return y.Command.Run(cmd)
+}

src/nodejs/yarn/yarn_test.go

@@ -144,4 +144,34 @@ var _ = Describe("Yarn", func() {
 			})
 		})
 	})
+
+	Describe("Rebuild", func() {
+		var oldNodeHome string
+
+		BeforeEach(func() {
+			oldNodeHome = os.Getenv("NODE_HOME")
+			Expect(os.Setenv("NODE_HOME", "test_node_home")).To(Succeed())
+		})
+
+		AfterEach(func() {
+			Expect(os.Setenv("NODE_HOME", oldNodeHome)).To(Succeed())
+		})
+
+		It("runs yarn rebuild with NODE_HOME set", func() {
+			mockCommand.EXPECT().Run(gomock.Any()).Do(func(cmd *exec.Cmd) {
+				Expect(cmd.Args).To(Equal([]string{"yarn", "rebuild"}))
+				Expect(cmd.Dir).To(Equal(buildDir))
+				Expect(cmd.Env).To(ContainElement("npm_config_nodedir=test_node_home"))
+			})
+
+			Expect(y.Rebuild(buildDir)).To(Succeed())
+			Expect(buffer.String()).To(ContainSubstring("Rebuilding any native modules (yarn)"))
+		})
+
+		It("propagates command errors", func() {
+			mockCommand.EXPECT().Run(gomock.Any()).Return(os.ErrNotExist)
+
+			Expect(y.Rebuild(buildDir)).To(Equal(os.ErrNotExist))
+		})
+	})
 })