Use function options pattern

pkg/cmd/auth/shared/login_flow.go

@@ -104,7 +104,7 @@ func Login(opts *LoginOptions) error {
 			}
 
 			if sshChoice {
-				keyPair, err := opts.sshContext.GenerateSSHKey("id_ed25519", true, promptForSshKeyPassphrase)
+				keyPair, err := opts.sshContext.GenerateSSHKey("id_ed25519", ssh.WithPassphrasePrompt(promptForSshKeyPassphrase))
 				if err != nil {
 					return err
 				}

pkg/cmd/codespace/ssh.go

@@ -124,7 +124,7 @@ func (a *App) SSH(ctx context.Context, sshArgs []string, opts sshOptions) (err e
 
 	sshContext := ssh.SshContext{}
 	if shouldGenerateSSHKeys(args, opts) && sshContext.HasKeygen() {
-		keyPair, err := sshContext.GenerateSSHKey("codespaces", false, nil)
+		keyPair, err := sshContext.GenerateSSHKey("codespaces", ssh.WithNoErrorOnExitingKey())
 		if err != nil {
 			return fmt.Errorf("failed to generate ssh keys: %s", err)
 		}

pkg/ssh/ssh_keys.go

@@ -36,16 +36,32 @@ func (c *SshContext) HasKeygen() bool {
 	return err == nil
 }
 
-func (c *SshContext) GenerateSSHKey(keyName string, errorOnExists bool, promptPassphrase func() (string, error)) (SshKeyPair, error) {
+type GenerateSSHKeyOptions struct {
+	noErrorOnExists  bool
+	promptPassphrase func() (string, error)
+}
+
+func WithNoErrorOnExitingKey() func(*GenerateSSHKeyOptions) {
+	return func(o *GenerateSSHKeyOptions) {
+		o.noErrorOnExists = false
+	}
+}
+
+func WithPassphrasePrompt(prompt func() (string, error)) func(*GenerateSSHKeyOptions) {
+	return func(o *GenerateSSHKeyOptions) {
+		o.promptPassphrase = prompt
+	}
+}
+
+func (c *SshContext) GenerateSSHKey(keyName string, configureOptions ...func(*GenerateSSHKeyOptions)) (*SshKeyPair, error) {
 	keygenExe, err := c.findKeygen()
 	if err != nil {
-		// TODO: is there a nicer way to do this default SshKeyPair?
-		return SshKeyPair{}, fmt.Errorf("could not find keygen executable")
+		return nil, fmt.Errorf("could not find keygen executable")
 	}
 
 	sshDir, err := c.sshDir()
 	if err != nil {
-		return SshKeyPair{}, err
+		return nil, err
 	}
 	keyFile := filepath.Join(sshDir, keyName)
 	keyPair := SshKeyPair{
@@ -53,29 +69,38 @@ func (c *SshContext) GenerateSSHKey(keyName string, errorOnExists bool, promptPa
 		PrivateKeyPath: keyFile,
 	}
 
+	opts := GenerateSSHKeyOptions{}
+	for _, configure := range configureOptions {
+		configure(&opts)
+	}
+
 	if _, err := os.Stat(keyFile); err == nil {
-		if errorOnExists {
-			return SshKeyPair{}, fmt.Errorf("refusing to overwrite file %s", keyFile)
+		if opts.noErrorOnExists {
+			return &keyPair, nil
 		} else {
-			return keyPair, nil
+			return nil, fmt.Errorf("refusing to overwrite file %s", keyFile)
 		}
 	}
 
 	if err := os.MkdirAll(filepath.Dir(keyFile), 0711); err != nil {
-		return SshKeyPair{}, err
+		return nil, err
 	}
 
 	var sshPassphrase string
-	if promptPassphrase != nil {
-		sshPassphrase, err = promptPassphrase()
+	if opts.promptPassphrase != nil {
+		sshPassphrase, err = opts.promptPassphrase()
 		if err != nil {
-			return SshKeyPair{}, err
+			return nil, err
 		}
 	}
 
-	// TOOD: sshLabel was never set, so should -C just be removed?
-	keygenCmd := exec.Command(keygenExe, "-t", "ed25519", "-C", "", "-N", sshPassphrase, "-f", keyFile)
-	return keyPair, run.PrepareCmd(keygenCmd).Run()
+	keygenCmd := exec.Command(keygenExe, "-t", "ed25519", "-N", sshPassphrase, "-f", keyFile)
+	err = run.PrepareCmd(keygenCmd).Run()
+	if err != nil {
+		return nil, err
+	}
+
+	return &keyPair, nil
 }
 
 func (c *SshContext) sshDir() (string, error) {