Avoid invoking token helper on login

changelog/313.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+cli/login: Avoid calling the token helper in `get` mode.
+```

command/base.go

@@ -73,9 +73,10 @@ type BaseCommand struct {
 	client *api.Client
 }
 
-// Client returns the HTTP API client. The client is cached on the command to
-// save performance on future calls.
-func (c *BaseCommand) Client() (*api.Client, error) {
+// Construct the HTTP API client, but do not set the token on it yet. This is to
+// avoid invoking the token helper for calls that do not need a token, such as
+// `vault login`.
+func (c *BaseCommand) ClientWithoutToken() (*api.Client, error) {
 	// Read the test client if present
 	if c.client != nil {
 		return c.client, nil
@@ -133,26 +134,6 @@ func (c *BaseCommand) Client() (*api.Client, error) {
 	// Set the wrapping function
 	client.SetWrappingLookupFunc(c.DefaultWrappingLookupFunc)
 
-	// Get the token if it came in from the environment
-	token := client.Token()
-
-	// If we don't have a token, check the token helper
-	if token == "" {
-		helper, err := c.TokenHelper()
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to get token helper")
-		}
-		token, err = helper.Get()
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to get token from token helper")
-		}
-	}
-
-	// Set the token
-	if token != "" {
-		client.SetToken(token)
-	}
-
 	client.SetMFACreds(c.flagMFA)
 
 	// flagNS takes precedence over flagNamespace. After resolution, point both
@@ -184,6 +165,42 @@ func (c *BaseCommand) Client() (*api.Client, error) {
 		}
 	}
 
+	return client, nil
+}
+
+// Client returns the HTTP API client. The client is cached on the command to
+// save performance on future calls.
+func (c *BaseCommand) Client() (*api.Client, error) {
+	// Read the test client if present
+	if c.client != nil {
+		return c.client, nil
+	}
+
+	client, err := c.ClientWithoutToken()
+	if err != nil {
+		return nil, err
+	}
+
+	// Get the token if it came in from the environment
+	token := client.Token()
+
+	// If we don't have a token, check the token helper
+	if token == "" {
+		helper, err := c.TokenHelper()
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to get token helper")
+		}
+		token, err = helper.Get()
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to get token from token helper")
+		}
+	}
+
+	// Set the token
+	if token != "" {
+		client.SetToken(token)
+	}
+
 	c.client = client
 
 	return client, nil

command/login.go

@@ -216,7 +216,7 @@ func (c *LoginCommand) Run(args []string) int {
 	}
 
 	// Create the client
-	client, err := c.Client()
+	client, err := c.ClientWithoutToken()
 	if err != nil {
 		c.UI.Error(err.Error())
 		return 2