many: remove usages of deprecated io/ioutil package (canonical#13768)

* many: remove usages of deprecated io/ioutil package

Signed-off-by: Miguel Pires <miguel.pires@canonical.com>

* .golangci.yml: remove errcheck ignore rule for io/ioutil

Signed-off-by: Miguel Pires <miguel.pires@canonical.com>

* run-checks: prevent new usages of io/ioutil

Signed-off-by: Miguel Pires <miguel.pires@canonical.com>

---------

Signed-off-by: Miguel Pires <miguel.pires@canonical.com>

Author: miguelpires

.golangci.yml

@@ -83,7 +83,7 @@ linters-settings:
     # [deprecated] comma-separated list of pairs of the form pkg:regex
     # the regex is used to ignore names within pkg. (default "fmt:.*").
     # see https://github.com/kisielk/errcheck#the-deprecated-method for details
-    ignore: fmt:.*,io/ioutil:^Read.*
+    ignore: fmt:.*
 
     # path to a file containing a list of functions to exclude from checking
     # see https://github.com/kisielk/errcheck#excluding-functions for details

asserts/database_test.go

@@ -25,7 +25,6 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -137,7 +136,7 @@ func (dbs *databaseSuite) TestImportKey(c *C) {
 	c.Check(info.Mode().Perm(), Equals, os.FileMode(0600)) // secret
 	// too much "clear box" testing? ok at least until we have
 	// more functionality
-	privKey, err := ioutil.ReadFile(keyPath)
+	privKey, err := os.ReadFile(keyPath)
 	c.Assert(err, IsNil)
 
 	privKeyFromDisk, err := asserts.DecodePrivateKeyInTest(privKey)

asserts/fsentryutils.go

@@ -21,7 +21,6 @@ package asserts
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -66,7 +65,7 @@ func entryExists(top string, subpath ...string) bool {
 
 func readEntry(top string, subpath ...string) ([]byte, error) {
 	fpath := filepath.Join(top, filepath.Join(subpath...))
-	return ioutil.ReadFile(fpath)
+	return os.ReadFile(fpath)
 }
 
 func removeEntry(top string, subpath ...string) error {

boot/flags.go

@@ -22,7 +22,6 @@ package boot
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -224,7 +223,7 @@ func BootFlags(dev snap.Device) ([]string, error) {
 	// bootenv are for this boot or the next one, but the initramfs will always
 	// copy the flags that were set into /run, so we always know the current
 	// boot's flags are written in /run
-	b, err := ioutil.ReadFile(snapBootFlagsFile)
+	b, err := os.ReadFile(snapBootFlagsFile)
 	if err != nil {
 		return nil, err
 	}
@@ -314,7 +313,7 @@ func HostUbuntuDataForMode(mode string, mod gadget.Model) ([]string, error) {
 		// host mount is snap-bootstrap's /run/snapd/snap-bootstrap/degraded.json, so
 		// we have to go parse that
 		degradedJSONFile := filepath.Join(dirs.SnapBootstrapRunDir, "degraded.json")
-		b, err := ioutil.ReadFile(degradedJSONFile)
+		b, err := os.ReadFile(degradedJSONFile)
 		if err != nil {
 			return nil, err
 		}

boot/modeenv_test.go

@@ -23,7 +23,6 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -209,7 +208,7 @@ base_status=try
 	err = dupDiskModeenv.Write()
 	c.Assert(err, IsNil)
 	c.Assert(dirs.SnapModeenvFileUnder(s.tmpdir), testutil.FilePresent)
-	origBytes, err := ioutil.ReadFile(dirs.SnapModeenvFileUnder(s.tmpdir) + ".orig")
+	origBytes, err := os.ReadFile(dirs.SnapModeenvFileUnder(s.tmpdir) + ".orig")
 	c.Assert(err, IsNil)
 	// the files should be the same
 	c.Assert(dirs.SnapModeenvFileUnder(s.tmpdir), testutil.FileEquals, string(origBytes))

bootloader/assets/genasset/main_test.go

@@ -22,7 +22,6 @@ package main_test
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -84,7 +83,7 @@ func (s *generateAssetsTestSuite) TestSimpleAsset(c *C) {
 	c.Assert(err, IsNil)
 	err = generate.Run("asset-name", filepath.Join(d, "in"), filepath.Join(d, "out"))
 	c.Assert(err, IsNil)
-	data, err := ioutil.ReadFile(filepath.Join(d, "out"))
+	data, err := os.ReadFile(filepath.Join(d, "out"))
 	c.Assert(err, IsNil)
 
 	const exp = `// -*- Mode: Go; indent-tabs-mode: t -*-

bootloader/assets/grub_test.go

@@ -22,7 +22,7 @@ package assets_test
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"testing"
 
 	. "gopkg.in/check.v1"
@@ -160,7 +160,7 @@ func (s *grubAssetsTestSuite) TestGrubAssetsWereRegenerated(c *C) {
 	} {
 		assetData := assets.Internal(tc.asset)
 		c.Assert(assetData, NotNil)
-		data, err := ioutil.ReadFile(tc.file)
+		data, err := os.ReadFile(tc.file)
 		c.Assert(err, IsNil)
 		c.Check(assetData, DeepEquals, data, Commentf("asset %q has not been updated", tc.asset))
 	}

bootloader/efi/efi.go

@@ -26,7 +26,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"unicode/utf16"
@@ -113,7 +112,7 @@ func ReadVarBytes(name string) ([]byte, VariableAttr, error) {
 		return nil, 0, cannotReadError(name, err)
 	}
 	defer varf.Close()
-	b, err := ioutil.ReadAll(varf)
+	b, err := io.ReadAll(varf)
 	if err != nil {
 		return nil, 0, cannotReadError(name, err)
 	}
@@ -173,7 +172,7 @@ func MockVars(vars map[string][]byte, attrs map[string]VariableAttr) (restore fu
 			if !ok {
 				attr = VariableRuntimeAccess | VariableBootServiceAccess
 			}
-			return ioutil.NopCloser(bytes.NewBuffer(val)), attr, int64(len(val)), nil
+			return io.NopCloser(bytes.NewBuffer(val)), attr, int64(len(val)), nil
 		}
 		return nil, 0, 0, fmt.Errorf("EFI variable %s not mocked", name)
 	}

bootloader/grubenv/grubenv.go

@@ -22,7 +22,6 @@ package grubenv
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"os"
 
 	"github.com/snapcore/snapd/strutil"
@@ -56,7 +55,7 @@ func (g *Env) Set(key, value string) {
 }
 
 func (g *Env) Load() error {
-	buf, err := ioutil.ReadFile(g.path)
+	buf, err := os.ReadFile(g.path)
 	if err != nil {
 		return err
 	}

bootloader/lk.go

@@ -22,7 +22,6 @@ package bootloader
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -444,7 +443,7 @@ func (l *lk) ExtractKernelAssets(s snap.PlaceInfo, snapf snap.Container) error {
 		// this is live system, extracted bootimg needs to be flashed to
 		// free bootimg partition and env has to be updated with
 		// new kernel snap to bootimg partition mapping
-		tmpdir, err := ioutil.TempDir("", "bootimg")
+		tmpdir, err := os.MkdirTemp("", "bootimg")
 		if err != nil {
 			return fmt.Errorf("cannot create temp directory: %v", err)
 		}