Refactoring ineffectual assignments

This patch fixed below 4 types of code line
1. Remove unnecessary variable assignment
2. Use variables declaration instead of explicit initial zero value
3. Change variable name to underbar when variable not used
4. Add erro check and return for ignored error

Signed-off-by: Daehyeok Mun <daehyeok@gmail.com>

api/types/filters/parse.go

@@ -79,8 +79,8 @@ func ToParamWithVersion(version string, a Args) (string, error) {
 	}
 
 	// for daemons older than v1.10, filter must be of the form map[string][]string
-	buf := []byte{}
-	err := errors.New("")
+	var buf []byte
+	var err error
 	if version != "" && versions.LessThan(version, "1.22") {
 		buf, err = json.Marshal(convertArgsToSlice(a.fields))
 	} else {

builder/dockerfile/dispatchers.go

@@ -204,10 +204,7 @@ func from(b *Builder, args []string, attributes map[string]bool, original string
 
 	name := args[0]
 
-	var (
-		image builder.Image
-		err   error
-	)
+	var image builder.Image
 
 	// Windows cannot support a container with no base image.
 	if name == api.NoBaseImageSpecifier {
@@ -219,10 +216,11 @@ func from(b *Builder, args []string, attributes map[string]bool, original string
 	} else {
 		// TODO: don't use `name`, instead resolve it to a digest
 		if !b.options.PullParent {
-			image, err = b.docker.GetImageOnBuild(name)
+			image, _ = b.docker.GetImageOnBuild(name)
 			// TODO: shouldn't we error out if error is different from "not found" ?
 		}
 		if image == nil {
+			var err error
 			image, err = b.docker.PullOnBuild(b.clientCtx, name, b.options.AuthConfigs, b.Output)
 			if err != nil {
 				return err

builder/dockerfile/internals.go

@@ -113,7 +113,6 @@ func (b *Builder) runContextCommand(args []string, allowRemote bool, allowLocalD
 	var err error
 	for _, orig := range args[0 : len(args)-1] {
 		var fi builder.FileInfo
-		decompress := allowLocalDecompression
 		if urlutil.IsURL(orig) {
 			if !allowRemote {
 				return fmt.Errorf("Source can't be a URL for %s", cmdName)
@@ -123,8 +122,10 @@ func (b *Builder) runContextCommand(args []string, allowRemote bool, allowLocalD
 				return err
 			}
 			defer os.RemoveAll(filepath.Dir(fi.Path()))
-			decompress = false
-			infos = append(infos, copyInfo{fi, decompress})
+			infos = append(infos, copyInfo{
+				FileInfo:   fi,
+				decompress: false,
+			})
 			continue
 		}
 		// not a URL

cli/command/container/stats_helpers.go

@@ -81,14 +81,11 @@ func collect(ctx context.Context, s *formatter.ContainerStats, cli client.APICli
 	go func() {
 		for {
 			var (
-				v                 *types.StatsJSON
-				memPercent        = 0.0
-				cpuPercent        = 0.0
-				blkRead, blkWrite uint64 // Only used on Linux
-				mem               = 0.0
-				memLimit          = 0.0
-				memPerc           = 0.0
-				pidsStatsCurrent  uint64
+				v                      *types.StatsJSON
+				memPercent, cpuPercent float64
+				blkRead, blkWrite      uint64 // Only used on Linux
+				mem, memLimit, memPerc float64
+				pidsStatsCurrent       uint64
 			)
 
 			if err := dec.Decode(&v); err != nil {

cli/command/plugin/create.go

@@ -41,7 +41,9 @@ func validateConfig(path string) error {
 // validateContextDir validates the given dir and returns abs path on success.
 func validateContextDir(contextDir string) (string, error) {
 	absContextDir, err := filepath.Abs(contextDir)
-
+	if err != nil {
+		return "", err
+	}
 	stat, err := os.Lstat(absContextDir)
 	if err != nil {
 		return "", err

daemon/daemon_unix.go

@@ -497,7 +497,7 @@ func UsingSystemd(config *Config) bool {
 // verifyPlatformContainerSettings performs platform-specific validation of the
 // hostconfig and config structures.
 func verifyPlatformContainerSettings(daemon *Daemon, hostConfig *containertypes.HostConfig, config *containertypes.Config, update bool) ([]string, error) {
-	warnings := []string{}
+	var warnings []string
 	sysInfo := sysinfo.New(true)
 
 	warnings, err := daemon.verifyExperimentalContainerSettings(hostConfig, config)
@@ -925,7 +925,6 @@ func parseRemappedRoot(usergrp string) (string, string, error) {
 			if err != nil {
 				return "", "", fmt.Errorf("Error during gid lookup for %q: %v", lookupName, err)
 			}
-			groupID = group.Gid
 			groupname = group.Name
 		}
 	}

daemon/oci_windows.go

@@ -64,7 +64,7 @@ func (daemon *Daemon) createSpec(c *container.Container) (*specs.Spec, error) {
 	s.Process.User.Username = c.Config.User
 
 	// In spec.Root. This is not set for Hyper-V containers
-	isHyperV := false
+	var isHyperV bool
 	if c.HostConfig.Isolation.IsDefault() {
 		// Container using default isolation, so take the default from the daemon configuration
 		isHyperV = daemon.defaultIsolation.IsHyperV()

distribution/push_v1.go

@@ -121,7 +121,7 @@ type v1DependencyImage struct {
 func newV1DependencyImage(l layer.Layer, parent *v1DependencyImage) *v1DependencyImage {
 	v1ID := digest.Digest(l.ChainID()).Hex()
 
-	config := ""
+	var config string
 	if parent != nil {
 		config = fmt.Sprintf(`{"id":"%s","parent":"%s"}`, v1ID, parent.V1ID())
 	} else {

pkg/chrootarchive/diff_unix.go

@@ -29,7 +29,7 @@ type applyLayerResponse struct {
 func applyLayer() {
 
 	var (
-		tmpDir  = ""
+		tmpDir  string
 		err     error
 		options *archive.TarOptions
 	)

pkg/testutil/utils.go

@@ -35,7 +35,6 @@ func IsKilled(err error) bool {
 }
 
 func runCommandWithOutput(cmd *exec.Cmd) (output string, exitCode int, err error) {
-	exitCode = 0
 	out, err := cmd.CombinedOutput()
 	exitCode = system.ProcessExitCode(err)
 	output = string(out)

registry/session.go

@@ -290,7 +290,7 @@ func (r *Session) GetRemoteImageLayer(imgID, registry string, imgSize int64) (io
 	if err != nil {
 		return nil, fmt.Errorf("Error while getting from the server: %v", err)
 	}
-	statusCode = 0
+
 	res, err = r.client.Do(req)
 	if err != nil {
 		logrus.Debugf("Error contacting registry %s: %v", registry, err)

volume/drivers/extpoint.go

@@ -200,12 +200,12 @@ func GetAllDrivers() ([]volume.Driver, error) {
 
 	for _, p := range plugins {
 		name := p.Name()
-		ext, ok := drivers.extensions[name]
-		if ok {
+
+		if _, ok := drivers.extensions[name]; ok {
 			continue
 		}
 
-		ext = NewVolumeDriver(name, p.BasePath(), p.Client())
+		ext := NewVolumeDriver(name, p.BasePath(), p.Client())
 		if p.IsV1() {
 			drivers.extensions[name] = ext
 		}