Pull request: all: rm var shadowing, vol. 1

Updates #2803.

Squashed commit of the following:

commit 15fa64ad4fb7561c4b0542245f99869685643bbd
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Mar 11 14:55:28 2021 +0300

    util: imp code

commit c3b0563a44ccc98a5901df19174acdca8a350d62
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Mar 11 14:38:54 2021 +0300

    all: rm var shadowing, vol. 1

internal/aghtest/os_windows.go

@@ -44,7 +44,7 @@ func prepareTestDir(t *testing.T) (dir string) {
 	t.Cleanup(func() {
 		start := time.Now()
 		for {
-			err := os.RemoveAll(dir)
+			err = os.RemoveAll(dir)
 			if err == nil {
 				break
 			}

internal/updater/updater.go

@@ -337,7 +337,8 @@ func tarGzFileUnpack(tarfile, outdir string) ([]string, error) {
 	var err2 error
 	tarReader := tar.NewReader(gzReader)
 	for {
-		header, err := tarReader.Next()
+		var header *tar.Header
+		header, err = tarReader.Next()
 		if err == io.EOF {
 			err2 = nil
 			break
@@ -377,7 +378,8 @@ func tarGzFileUnpack(tarfile, outdir string) ([]string, error) {
 			continue
 		}
 
-		f, err := os.OpenFile(outputName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.FileMode(header.Mode&0o777))
+		var f io.WriteCloser
+		f, err = os.OpenFile(outputName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.FileMode(header.Mode&0o777))
 		if err != nil {
 			err2 = fmt.Errorf("os.OpenFile(%s): %w", outputName, err)
 			break
@@ -449,7 +451,8 @@ func zipFileUnpack(zipfile, outdir string) ([]string, error) {
 			continue
 		}
 
-		f, err := os.OpenFile(outputName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, fi.Mode())
+		var f io.WriteCloser
+		f, err = os.OpenFile(outputName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, fi.Mode())
 		if err != nil {
 			err2 = fmt.Errorf("os.OpenFile(): %w", err)
 			break

internal/util/autohosts.go

@@ -10,10 +10,9 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/miekg/dns"
-
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/fsnotify/fsnotify"
+	"github.com/miekg/dns"
 )
 
 type onChangedT func()
@@ -228,15 +227,17 @@ func (a *AutoHosts) load(table map[string][]net.IP, tableRev map[string][]string
 	r := bufio.NewReader(f)
 	log.Debug("AutoHosts: loading hosts from file %s", fn)
 
-	finish := false
-	for !finish {
-		line, err := r.ReadString('\n')
+	for done := false; !done; {
+		var line string
+		line, err = r.ReadString('\n')
 		if err == io.EOF {
-			finish = true
+			done = true
 		} else if err != nil {
 			log.Error("AutoHosts: %s", err)
+
 			return
 		}
+
 		line = strings.TrimSpace(line)
 		if len(line) == 0 || line[0] == '#' {
 			continue
@@ -247,26 +248,30 @@ func (a *AutoHosts) load(table map[string][]net.IP, tableRev map[string][]string
 			continue
 		}
 
-		ipAddr := net.ParseIP(fields[0])
-		if ipAddr == nil {
+		ip := net.ParseIP(fields[0])
+		if ip == nil {
 			continue
 		}
+
 		for i := 1; i != len(fields); i++ {
 			host := fields[i]
 			if len(host) == 0 {
 				break
 			}
+
 			sharp := strings.IndexByte(host, '#')
 			if sharp == 0 {
-				break // skip the rest of the line after #
+				// Skip the comments.
+				break
 			} else if sharp > 0 {
 				host = host[:sharp]
 			}
 
-			a.updateTable(table, host, ipAddr)
-			a.updateTableRev(tableRev, host, ipAddr)
+			a.updateTable(table, host, ip)
+			a.updateTableRev(tableRev, host, ip)
 			if sharp >= 0 {
-				break // skip the rest of the line after #
+				// Skip the comments again.
+				break
 			}
 		}
 	}

internal/util/helpers.go

@@ -94,7 +94,8 @@ func IsOpenWRT() bool {
 			continue
 		}
 
-		body, err := ioutil.ReadFile(filepath.Join(etcDir, fileInfo.Name()))
+		var body []byte
+		body, err = ioutil.ReadFile(filepath.Join(etcDir, fileInfo.Name()))
 		if err != nil {
 			continue
 		}

internal/util/network.go

@@ -69,7 +69,8 @@ func GetValidNetInterfacesForWeb() ([]*NetInterface, error) {
 	var netInterfaces []*NetInterface
 
 	for _, iface := range ifaces {
-		addrs, err := iface.Addrs()
+		var addrs []net.Addr
+		addrs, err = iface.Addrs()
 		if err != nil {
 			return nil, fmt.Errorf("failed to get addresses for interface %s: %w", iface.Name, err)
 		}

internal/util/tls.go

@@ -32,19 +32,24 @@ func LoadSystemRootCAs() *x509.CertPool {
 			if !os.IsNotExist(err) {
 				log.Error("Opening directory: %s: %s", dir, err)
 			}
+
 			continue
 		}
+
 		rootsAdded := false
 		for _, fi := range fis {
-			data, err := ioutil.ReadFile(dir + "/" + fi.Name())
-			if err == nil && roots.AppendCertsFromPEM(data) {
+			var certData []byte
+			certData, err = ioutil.ReadFile(dir + "/" + fi.Name())
+			if err == nil && roots.AppendCertsFromPEM(certData) {
 				rootsAdded = true
 			}
 		}
+
 		if rootsAdded {
 			return roots
 		}
 	}
+
 	return nil
 }