fix: various improvements to setup command (#20155)

When checking for existing configs, check the length of the array after
parsing. There could be an empty config file present.

If --name was specified then use that as the configuration name, regardless of
whether or not there are existing configs.

Allow a 0 (infinite) retention to be specified with --retention when in
interactive mode.

Co-authored-by: Dan Moran <dmoran@influxdata.com>

CHANGELOG.md

@@ -31,6 +31,8 @@ want to use the default.
 1. [20166](https://github.com/influxdata/influxdb/pull/20166): Enforce max value of 2147483647 on query queue size to avoid startup panic.
 1. [20182](https://github.com/influxdata/influxdb/pull/20182): Auto-migrate existing DBRP mappings from old schema to avoid panic.
 1. [20202](https://github.com/influxdata/influxdb/pull/20202): Optimize shard lookup in groups containing only one shard. Thanks @StoneYunZhao!
+1. [20155](https://github.com/influxdata/influxdb/pull/20155): Respect the `--name` option in `influx setup` whether configs already exist or not.
+1. [20155](https://github.com/influxdata/influxdb/pull/20155): Allow for 0 (infinite) values for `--retention` in `influx setup`.
 
 ## v2.0.2 [2020-11-18]
 ----------------------

cmd/influx/setup.go

@@ -141,24 +141,13 @@ func setupF(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("instance at %q has already been setup", activeConfig.Host)
 	}
 
-	existingConfigs := make(config.Configs)
-	if _, err := os.Stat(dPath); err == nil {
-		existingConfigs, _ = localConfigSVC.ListConfigs()
-		// ignore the error if found nothing
-		if setupFlags.name == "" {
-			return errors.New("flag name is required if you already have existing configs")
-		}
-		if _, ok := existingConfigs[setupFlags.name]; ok {
-			return &influxdb.Error{
-				Code: influxdb.EConflict,
-				Msg:  fmt.Sprintf("config name %q already existed", setupFlags.name),
-			}
-		}
+	if err := validateNoNameCollision(localConfigSVC, setupFlags.name); err != nil {
+		return err
 	}
 
 	req, err := onboardingRequest()
 	if err != nil {
-		return fmt.Errorf("failed to retrieve data to setup instance: %v", err)
+		return fmt.Errorf("failed to setup instance: %v", err)
 	}
 
 	result, err := s.OnboardInitialUser(context.Background(), req)
@@ -169,7 +158,7 @@ func setupF(cmd *cobra.Command, args []string) error {
 	p := config.DefaultConfig
 	p.Token = result.Auth.Token
 	p.Org = result.Org.Name
-	if len(existingConfigs) > 0 {
+	if setupFlags.name != "" {
 		p.Name = setupFlags.name
 	}
 	if activeConfig.Host != "" {
@@ -206,6 +195,29 @@ func setupF(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
+// validateNoNameCollision asserts that there isn't already a local config with a given name.
+func validateNoNameCollision(localConfigSvc config.Service, configName string) error {
+	existingConfigs, err := localConfigSvc.ListConfigs()
+	if err != nil {
+		return fmt.Errorf("error checking existing configs: %v", err)
+	}
+	if len(existingConfigs) == 0 {
+		return nil
+	}
+
+	// If there are existing configs then require that a name be
+	// specified in order to distinguish this new config from what's
+	// there already.
+	if configName == "" {
+		return errors.New("flag name is required if you already have existing configs")
+	}
+	if _, ok := existingConfigs[configName]; ok {
+		return fmt.Errorf("config name %q already exists", configName)
+	}
+
+	return nil
+}
+
 func isInteractive() bool {
 	return !setupFlags.force ||
 		setupFlags.username == "" ||
@@ -277,12 +289,11 @@ func interactive() (req *influxdb.OnboardingRequest, err error) {
 		req.Bucket = internal2.GetInput(ui, "Please type your primary bucket name", "")
 	}
 
-	dur, err := internal2.RawDurationToTimeDuration(setupFlags.retention)
-	if err != nil {
-		return nil, err
-	}
-
-	if dur > 0 {
+	if setupFlags.retention != "" {
+		dur, err := internal2.RawDurationToTimeDuration(setupFlags.retention)
+		if err != nil {
+			return nil, err
+		}
 		req.RetentionPeriod = dur
 	} else {
 		for {