stembuild: simplify main()

- parse args early
  - print error if arg parsing fails
- print version info early if requested
- simplify Messenger struct
- use one context.Background()
- use defer to remove stemcell automation artifact

As part of this the environment_variable_warnings_test is updated
because the output of `stembuild version` is printed before the ENV vars
are validated.

Author: aramprice

stembuild/integration/environment_variable_warnings_test.go

@@ -10,9 +10,6 @@ import (
 )
 
 var _ = Describe("Environment Variables Warning", func() {
-	var (
-		stembuildExecutable string
-	)
 	BeforeEach(func() {
 		var err error
 		stembuildExecutable, err = helpers.BuildStembuild("0.0.0")
@@ -21,17 +18,18 @@ var _ = Describe("Environment Variables Warning", func() {
 
 	When("Environment variables starting with GOVC_* or GOVMOMI_* are set", func() {
 		It("should print a warning for each GOVC_* environment variable", func() {
-			session := helpers.StembuildWithEnv(map[string]string{"GOVC_BANANA": "I AM A BANANA", "GOVMOMI_POTATO": "THIS IS A POTATO"}, stembuildExecutable, "--version")
+			session := helpers.StembuildWithEnv(map[string]string{"GOVC_BANANA": "I AM A BANANA", "GOVMOMI_POTATO": "THIS IS A POTATO"}, stembuildExecutable, "package")
 			Eventually(session.Err).Should(Say("Warning: The following environment variable is set and might override flags provided to stembuild: GOVC_BANANA\n"))
 			Consistently(session.Err).ShouldNot(Say("I AM A BANANA"))
-			Eventually(session).Should(Exit(0))
+			Eventually(session).Should(Exit(1))
 		})
 
 		It("should print a warning for each GOVMOMI_* environment variable", func() {
-			session := helpers.StembuildWithEnv(map[string]string{"GOVC_BANANA": "I AM A BANANA", "GOVMOMI_POTATO": "THIS IS A POTATO"}, stembuildExecutable, "--version")
+			session := helpers.StembuildWithEnv(map[string]string{"GOVC_BANANA": "I AM A BANANA", "GOVMOMI_POTATO": "THIS IS A POTATO"}, stembuildExecutable, "package")
+
 			Eventually(session.Err).Should(Say("Warning: The following environment variable is set and might override flags provided to stembuild: GOVMOMI_POTATO\n"))
 			Consistently(session.Err).ShouldNot(Say("THIS IS A POTATO"))
-			Eventually(session).Should(Exit(0))
+			Eventually(session).Should(Exit(1))
 		})
 	})
 })

stembuild/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"flag"
+	"fmt"
 	"os"
 	"path"
 	"strings"
@@ -26,9 +27,25 @@ func main() {
 	fs.BoolVar(&gf.Color, "color", false, "Colorize debug output")
 	fs.BoolVar(&gf.ShowVersion, "version", false, "Show Stembuild version")
 	fs.BoolVar(&gf.ShowVersion, "v", false, "Stembuild version (shorthand)")
+
 	commander := subcommands.NewCommander(fs, path.Base(os.Args[0]))
 
 	stembuildMessenger := messenger.NewStembuildMessenger(commander.Output, commander.Error)
+
+	stembuildExecutable := path.Base(os.Args[0])
+	stembuildArgs := os.Args[1:]
+
+	err := fs.Parse(stembuildArgs)
+	if err != nil {
+		stembuildMessenger.PrintErr(fmt.Sprintf("Unable to parse args: %v", stembuildArgs))
+		os.Exit(1)
+	}
+
+	if gf.ShowVersion {
+		stembuildMessenger.PrintOut(fmt.Sprintf("%s version %s, Windows Stemcell Building Tool\n\n", stembuildExecutable, version.Current))
+		os.Exit(0)
+	}
+
 	logLevel := colorlogger.NONE
 	if gf.Debug {
 		logLevel = colorlogger.DEBUG
@@ -39,16 +56,19 @@ func main() {
 	for _, env := range envs {
 		envName := strings.Split(env, "=")[0]
 		if strings.HasPrefix(envName, "GOVC_") || strings.HasPrefix(envName, "GOVMOMI_") {
-			stembuildMessenger.EnvironmentVariableWarning(envName)
+			stembuildMessenger.PrintErr(fmt.Sprintf("Warning: The following environment variable is set and might override flags provided to stembuild: %s\n", envName))
 		}
 	}
 
 	s := "./StemcellAutomation.zip"
-	err := os.WriteFile(s, assets.StemcellAutomation, 0644)
+	err = os.WriteFile(s, assets.StemcellAutomation, 0644)
 	if err != nil {
-		stembuildMessenger.StemcellAutomationWarning()
+		stembuildMessenger.PrintErr("Unable to write StemcellAutomation.zip")
 		os.Exit(1)
 	}
+	defer os.Remove(s) //nolint:errcheck
+
+	ctx := context.Background()
 
 	var commands []subcommands.Command
 	helpCmd := commandparser.NewStembuildHelp(commander, fs, &commands)
@@ -60,23 +80,13 @@ func main() {
 	commander.Register(packageCmd, "")
 	commands = append(commands, packageCmd)
 
-	constructCmd := commandparser.NewConstructCmd(context.Background(), &construct.Factory{}, &vcenter_manager.ManagerFactory{}, &commandparser.ConstructValidator{}, stembuildMessenger)
+	constructCmd := commandparser.NewConstructCmd(ctx, &construct.Factory{}, &vcenter_manager.ManagerFactory{}, &commandparser.ConstructValidator{}, stembuildMessenger)
 	constructCmd.GlobalFlags = &gf
 	commander.Register(constructCmd, "")
 	commands = append(commands, constructCmd)
 
 	// Override the default usage text of Google's Subcommand with our own
 	fs.Usage = func() { helpCmd.Explain(commander.Error) }
 
-	fs.Parse(os.Args[1:]) //nolint:errcheck
-	if gf.ShowVersion {
-		stembuildMessenger.VersionInfo(path.Base(os.Args[0]), version.Current)
-		os.Remove(s) //nolint:errcheck
-		os.Exit(0)
-	}
-
-	ctx := context.Background()
-	i := int(commander.Execute(ctx))
-	os.Remove(s) //nolint:errcheck
-	os.Exit(i)
+	os.Exit(int(commander.Execute(ctx)))
 }

stembuild/messenger/stembuild_messenger.go

@@ -1,7 +1,6 @@
 package messenger
 
 import (
-	"fmt"
 	"io"
 )
 
@@ -21,15 +20,3 @@ func (m *StembuildMessenger) PrintOut(message string) {
 func (m *StembuildMessenger) PrintErr(message string) {
 	write(m.stderr, message)
 }
-
-func (m *StembuildMessenger) VersionInfo(executable string, version string) {
-	write(m.stdout, fmt.Sprintf("%s version %s, Windows Stemcell Building Tool\n\n", executable, version))
-}
-
-func (m *StembuildMessenger) EnvironmentVariableWarning(envVarName string) {
-	write(m.stderr, fmt.Sprintf("Warning: The following environment variable is set and might override flags provided to stembuild: %s\n", envVarName))
-}
-
-func (m *StembuildMessenger) StemcellAutomationWarning() {
-	write(m.stderr, "Unable to write StemcellAutomation.zip")
-}

stembuild/messenger/stembuild_messenger_test.go

@@ -1,8 +1,6 @@
 package messenger_test
 
 import (
-	"fmt"
-
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 	. "github.com/onsi/gomega/gbytes"
@@ -40,39 +38,4 @@ var _ = Describe("StembuildMessenger", func() {
 			Eventually(errBuf).Should(Say(message))
 		})
 	})
-
-	Describe("EnvironmentVariableWarning", func() {
-		It("outputs the expected warning to stderr", func() {
-			envVar := "SOME_VAR"
-			m.EnvironmentVariableWarning(envVar)
-
-			Eventually(errBuf).Should(Say(fmt.Sprintf("Warning: The following environment variable is set and might override flags provided to stembuild: %s\n", envVar)))
-		})
-	})
-
-	Describe("StemcellAutomationWarning", func() {
-		It("outputs the expected warning to stderr", func() {
-			m.StemcellAutomationWarning()
-
-			Eventually(errBuf).Should(Say("Unable to write StemcellAutomation.zip"))
-		})
-	})
-
-	Describe("StemcellAutomationWarning", func() {
-		It("outputs the expected warning to stderr", func() {
-			m.StemcellAutomationWarning()
-
-			Eventually(errBuf).Should(Say("Unable to write StemcellAutomation.zip"))
-		})
-	})
-
-	Describe("PrintVersionInfo", func() {
-		It("outputs the expected value to stdout", func() {
-			executable := "custom-stembuild"
-			version := "my.custom.version"
-			m.VersionInfo(executable, version)
-
-			Eventually(outBuf).Should(Say(fmt.Sprintf("%s version %s, Windows Stemcell Building Tool\n\n", executable, version)))
-		})
-	})
 })