Fix volume Create to check against canonical driver name

Previously, it was comparing against the driver name passed in by the
caller. This could lead to subtle issues when using plugins, like
"plugin" vs. "plugin:latest".

Also, remove "conflict:" prefix to improve the error message.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

integration-cli/docker_cli_external_volume_driver_unix_test.go

@@ -284,6 +284,22 @@ func (s *DockerExternalVolumeSuite) TearDownSuite(c *check.C) {
 	c.Assert(err, checker.IsNil)
 }
 
+func (s *DockerExternalVolumeSuite) TestVolumeCLICreateOptionConflict(c *check.C) {
+	dockerCmd(c, "volume", "create", "test")
+
+	out, _, err := dockerCmdWithError("volume", "create", "test", "--driver", volumePluginName)
+	c.Assert(err, check.NotNil, check.Commentf("volume create exception name already in use with another driver"))
+	c.Assert(out, checker.Contains, "A volume named test already exists")
+
+	out, _ = dockerCmd(c, "volume", "inspect", "--format={{ .Driver }}", "test")
+	_, _, err = dockerCmdWithError("volume", "create", "test", "--driver", strings.TrimSpace(out))
+	c.Assert(err, check.IsNil)
+
+	// make sure hidden --name option conflicts with positional arg name
+	out, _, err = dockerCmdWithError("volume", "create", "--name", "test2", "test2")
+	c.Assert(err, check.NotNil, check.Commentf("Conflicting options: either specify --name or provide positional arg, not both"))
+}
+
 func (s *DockerExternalVolumeSuite) TestExternalVolumeDriverNamed(c *check.C) {
 	s.d.StartWithBusybox(c)
 

integration-cli/docker_cli_volume_test.go

@@ -29,21 +29,6 @@ func (s *DockerSuite) TestVolumeCLICreate(c *check.C) {
 	c.Assert(name, check.Equals, "test2")
 }
 
-func (s *DockerSuite) TestVolumeCLICreateOptionConflict(c *check.C) {
-	dockerCmd(c, "volume", "create", "test")
-	out, _, err := dockerCmdWithError("volume", "create", "test", "--driver", "nosuchdriver")
-	c.Assert(err, check.NotNil, check.Commentf("volume create exception name already in use with another driver"))
-	c.Assert(out, checker.Contains, "A volume named test already exists")
-
-	out, _ = dockerCmd(c, "volume", "inspect", "--format={{ .Driver }}", "test")
-	_, _, err = dockerCmdWithError("volume", "create", "test", "--driver", strings.TrimSpace(out))
-	c.Assert(err, check.IsNil)
-
-	// make sure hidden --name option conflicts with positional arg name
-	out, _, err = dockerCmdWithError("volume", "create", "--name", "test2", "test2")
-	c.Assert(err, check.NotNil, check.Commentf("Conflicting options: either specify --name or provide positional arg, not both"))
-}
-
 func (s *DockerSuite) TestVolumeCLIInspect(c *check.C) {
 	c.Assert(
 		exec.Command(dockerBinary, "volume", "inspect", "doesntexist").Run(),

volume/store/errors.go

@@ -14,7 +14,7 @@ var (
 	// errInvalidName is a typed error returned when creating a volume with a name that is not valid on the platform
 	errInvalidName = errors.New("volume name is not valid on this platform")
 	// errNameConflict is a typed error returned on create when a volume exists with the given name, but for a different driver
-	errNameConflict = errors.New("conflict: volume name must be unique")
+	errNameConflict = errors.New("volume name must be unique")
 )
 
 // OpErr is the error type returned by functions in the store package. It describes

volume/store/store.go

@@ -309,8 +309,17 @@ func (s *VolumeStore) checkConflict(name, driverName string) (volume.Volume, err
 
 	vDriverName := v.DriverName()
 	var conflict bool
-	if driverName != "" && vDriverName != driverName {
-		conflict = true
+	if driverName != "" {
+		// Retrieve canonical driver name to avoid inconsistencies (for example
+		// "plugin" vs. "plugin:latest")
+		vd, err := volumedrivers.GetDriver(driverName)
+		if err != nil {
+			return nil, err
+		}
+
+		if vDriverName != vd.Name() {
+			conflict = true
+		}
 	}
 
 	// let's check if the found volume ref