From d5490a8fb80f67c821fec1c8d426f8d64cd77160 Mon Sep 17 00:00:00 2001
From: Priya Wadhwa <priyawadhwa@google.com>
Date: Tue, 17 Mar 2020 16:03:29 -0700
Subject: [PATCH] Move driver validation before driver selection

If a user passes in a driver via --vm-driver or --driver, then we should make sure it matches the preexisting cluster (if one exists) before we try and get information about the driver. This avoids confusing logs where we tell the user we're using the preexisting driver but then error out because they specified a different driver.
---
 cmd/minikube/cmd/start.go | 90 ++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 40 deletions(-)

diff --git a/cmd/minikube/cmd/start.go b/cmd/minikube/cmd/start.go
index 44e3d3210c..13ea4c891f 100644
--- a/cmd/minikube/cmd/start.go
+++ b/cmd/minikube/cmd/start.go
@@ -294,6 +294,7 @@ func runStart(cmd *cobra.Command, args []string) {
 		exit.WithCodeT(exit.Data, "Unable to load config: {{.error}}", out.V{"error": err})
 	}
 
+	validateSpecifiedDriver(existing)
 	ds := selectDriver(existing)
 	driverName := ds.Name
 	glog.Infof("selected driver: %s", driverName)
@@ -482,6 +483,55 @@ func selectDriver(existing *config.ClusterConfig) registry.DriverState {
 	return pick
 }
 
+// validateSpecifiedDriver makes sure that if a user has passed in a driver
+// it matches the existing cluster if there is one
+func validateSpecifiedDriver(existing *config.ClusterConfig) {
+	if existing == nil {
+		return
+	}
+	old := existing.Driver
+	var requested string
+	if d := viper.GetString("driver"); d != "" {
+		requested = d
+	} else if d := viper.GetString("vm-driver"); d != "" {
+		requested = d
+	}
+	if old == requested {
+		return
+	}
+
+	api, err := machine.NewAPIClient()
+	if err != nil {
+		glog.Warningf("selectDriver NewAPIClient: %v", err)
+		return
+	}
+
+	cp, err := config.PrimaryControlPlane(existing)
+	if err != nil {
+		exit.WithError("Error getting primary cp", err)
+	}
+	machineName := driver.MachineName(*existing, cp)
+	h, err := api.Load(machineName)
+	if err != nil {
+		glog.Warningf("selectDriver api.Load: %v", err)
+		return
+	}
+
+	out.ErrT(out.Conflict, `The existing "{{.profile_name}}" VM was created using the "{{.old_driver}}" driver, and is incompatible with the "{{.driver}}" driver.`,
+		out.V{"profile_name": machineName, "driver": requested, "old_driver": h.Driver.DriverName()})
+
+	out.ErrT(out.Workaround, `To proceed, either:
+
+1) Delete the existing "{{.profile_name}}" cluster using: '{{.command}} delete'
+
+* or *
+
+2) Start the existing "{{.profile_name}}" cluster using: '{{.command}} start --driver={{.old_driver}}'
+`, out.V{"command": minikubeCmd(), "old_driver": h.Driver.DriverName(), "profile_name": machineName})
+
+	exit.WithCodeT(exit.Config, "Exiting.")
+}
+
 // validateDriver validates that the selected driver appears sane, exits if not
 func validateDriver(ds registry.DriverState, existing *config.ClusterConfig) {
 	name := ds.Name
@@ -510,46 +560,6 @@ func validateDriver(ds registry.DriverState, existing *config.ClusterConfig) {
 			exit.WithCodeT(exit.Unavailable, "{{.driver}} does not appear to be installed", out.V{"driver": name})
 		}
 	}
-
-	if existing == nil {
-		return
-	}
-
-	api, err := machine.NewAPIClient()
-	if err != nil {
-		glog.Warningf("selectDriver NewAPIClient: %v", err)
-		return
-	}
-
-	cp, err := config.PrimaryControlPlane(existing)
-	if err != nil {
-		exit.WithError("Error getting primary cp", err)
-	}
-
-	machineName := driver.MachineName(*existing, cp)
-	h, err := api.Load(machineName)
-	if err != nil {
-		glog.Warningf("selectDriver api.Load: %v", err)
-		return
-	}
-
-	if h.Driver.DriverName() == name {
-		return
-	}
-
-	out.ErrT(out.Conflict, `The existing "{{.profile_name}}" VM that was created using the "{{.old_driver}}" driver, and is incompatible with the "{{.driver}}" driver.`,
-		out.V{"profile_name": machineName, "driver": name, "old_driver": h.Driver.DriverName()})
-
-	out.ErrT(out.Workaround, `To proceed, either:
-
-    1) Delete the existing "{{.profile_name}}" cluster using: '{{.command}} delete'
-
-    * or *
-
-    2) Start the existing "{{.profile_name}}" cluster using: '{{.command}} start --driver={{.old_driver}}'
-	`, out.V{"command": minikubeCmd(), "old_driver": h.Driver.DriverName(), "profile_name": machineName})
-
-	exit.WithCodeT(exit.Config, "Exiting.")
 }
 
 func selectImageRepository(mirrorCountry string, v semver.Version) (bool, string, error) {