Enable more linters

.golangci.yml

@@ -9,9 +9,23 @@ linters:
     - staticcheck
     - whitespace
     - wrapcheck
-  exclusions:
-    presets:
-      - comments
+    - ineffassign
+    - unused
+    - unconvert
+    - bodyclose
+    - copyloopvar
+    - nilerr
+    - nilnil
+    - wastedassign
+    - maintidx
+    - nakedret
+    - predeclared
+    - gocritic
+    - prealloc
+    - noctx
+    - testifylint
+    - unparam
 formatters:
   enable:
-    - gofmt
+    - gofumpt
+    - goimports

backend.go

@@ -1,6 +1,8 @@
 //go:build linux
 // +build linux
 
+// Package fakemachine provides a lightweight virtual machine abstraction for
+// running commands in an isolated environment.
 package fakemachine
 
 import (
@@ -15,13 +17,14 @@ func implementedBackends(m *Machine) []backend {
 	}
 }
 
-/* A list of backends which are implemented - sorted in order in which the
- * "auto" backend chooses them.
- */
+// BackendNames returns the list of implemented backends sorted in order of
+// preference for the "auto" selection algorithm, with "auto" prepended.
 func BackendNames() []string {
-	names := []string{"auto"}
+	backends := implementedBackends(nil)
+	names := make([]string, 0, 1+len(backends))
+	names = append(names, "auto")
 
-	for _, backend := range implementedBackends(nil) {
+	for _, backend := range backends {
 		names = append(names, backend.Name())
 	}
 

backend_qemu.go

@@ -177,7 +177,7 @@ func (b qemuBackend) ModulePath() (string, error) {
 }
 
 func (b qemuBackend) UdevRules() []string {
-	udevRules := []string{}
+	udevRules := make([]string, 0, 2*len(b.machine.images))
 
 	// create symlink under /dev/disk/by-fakemachine-label/ for each virtual image
 	for i, img := range b.machine.images {
@@ -228,14 +228,16 @@ func (b qemuBackend) StartQemu(kvm bool) (bool, error) {
 	}
 	memory := fmt.Sprintf("%d", m.memory)
 	numcpus := fmt.Sprintf("%d", m.numcpus)
-	qemuargs := []string{qemuMachine.binary,
+	qemuargs := []string{
+		qemuMachine.binary,
 		"-smp", numcpus,
 		"-m", memory,
 		"-kernel", kernelPath,
 		"-initrd", m.initrdpath,
 		"-display", "none",
 		"-nic", "user,model=virtio-net-pci",
-		"-no-reboot"}
+		"-no-reboot",
+	}
 
 	if kvm {
 		qemuargs = append(qemuargs,
@@ -247,9 +249,11 @@ func (b qemuBackend) StartQemu(kvm bool) (bool, error) {
 
 	qemuargs = append(qemuargs, "-machine", qemuMachine.machine)
 	console := fmt.Sprintf("console=%s", qemuMachine.console)
-	kernelargs := []string{console, "panic=-1",
+	kernelargs := []string{
+		console, "panic=-1",
 		"plymouth.enable=0",
-		"systemd.unit=fakemachine.service"}
+		"systemd.unit=fakemachine.service",
+	}
 
 	if m.showBoot {
 		// Create a character device representing our stdio

cmd/fakemachine/main.go

@@ -1,15 +1,18 @@
+// Package main is the entry point for the fakemachine command-line tool.
 package main
 
 import (
-	"al.essio.dev/pkg/shellescape"
 	"errors"
 	"fmt"
-	"github.com/docker/go-units"
-	"github.com/go-debos/fakemachine"
-	"github.com/jessevdk/go-flags"
 	"os"
 	"runtime/debug"
 	"strings"
+
+	"al.essio.dev/pkg/shellescape"
+
+	"github.com/docker/go-units"
+	"github.com/go-debos/fakemachine"
+	"github.com/jessevdk/go-flags"
 )
 
 var Version string
@@ -28,8 +31,10 @@ type Options struct {
 	Version     bool              `long:"version" description:"Print fakemachine version"`
 }
 
-var options Options
-var parser = flags.NewParser(&options, flags.Default)
+var (
+	options Options
+	parser  = flags.NewParser(&options, flags.Default)
+)
 
 func determineVersionFromBuild() string {
 	info, ok := debug.ReadBuildInfo()
@@ -131,7 +136,7 @@ func SetupEnviron(m *fakemachine.Machine, options Options) {
 	// These are the environment variables that will be detected on the
 	// host and propagated to fakemachine. These are listed lower case, but
 	// they are detected and configured in both lower case and upper case.
-	var environVars = [...]string{
+	environVars := [...]string{
 		"http_proxy",
 		"https_proxy",
 		"ftp_proxy",
@@ -166,7 +171,7 @@ func SetupEnviron(m *fakemachine.Machine, options Options) {
 	}
 
 	// Puts in a format that is compatible with output of os.Environ()
-	EnvironString := []string{}
+	EnvironString := make([]string, 0, len(EnvironVars))
 	for k, v := range EnvironVars {
 		warnLocalhost(k, v)
 		EnvironString = append(EnvironString, fmt.Sprintf("%s=%s", k, v))

cpio/writerhelper.go

@@ -1,3 +1,4 @@
+// Package writerhelper provides helpers for writing cpio archives.
 package writerhelper
 
 import (
@@ -10,27 +11,33 @@ import (
 	"path/filepath"
 	"strings"
 
-	"github.com/surma/gocpio"
+	cpio "github.com/surma/gocpio"
 )
 
+// WriterHelper wraps a cpio.Writer and tracks written paths to automatically
+// create parent directories as needed.
 type WriterHelper struct {
 	paths map[string]bool
 	*cpio.Writer
 }
 
+// WriteDirectory describes a directory entry to add to the archive.
 type WriteDirectory struct {
 	Directory string
 	Perm      os.FileMode
 }
 
+// WriteSymlink describes a symbolic link entry to add to the archive.
 type WriteSymlink struct {
 	Target string
 	Link   string
 	Perm   os.FileMode
 }
 
+// Transformer is a function that transforms data from src and writes it to dst.
 type Transformer func(dst io.Writer, src io.Reader) error
 
+// NewWriterHelper creates a WriterHelper that writes a cpio archive to f.
 func NewWriterHelper(f io.Writer) *WriterHelper {
 	return &WriterHelper{
 		paths:  map[string]bool{"/": true},
@@ -54,7 +61,7 @@ func (w *WriterHelper) ensureBaseDirectory(directory string) error {
 			continue
 		}
 
-		err := w.WriteDirectory(collector, 0755)
+		err := w.WriteDirectory(collector, 0o755)
 		if err != nil {
 			return err
 		}
@@ -63,6 +70,7 @@ func (w *WriterHelper) ensureBaseDirectory(directory string) error {
 	return nil
 }
 
+// WriteDirectories writes multiple directory entries to the archive.
 func (w *WriterHelper) WriteDirectories(directories []WriteDirectory) error {
 	for _, d := range directories {
 		err := w.WriteDirectory(d.Directory, d.Perm)
@@ -73,6 +81,7 @@ func (w *WriterHelper) WriteDirectories(directories []WriteDirectory) error {
 	return nil
 }
 
+// WriteDirectory writes a single directory entry, creating parent directories as needed.
 func (w *WriterHelper) WriteDirectory(directory string, perm os.FileMode) error {
 	err := w.ensureBaseDirectory(path.Dir(directory))
 	if err != nil {
@@ -94,10 +103,12 @@ func (w *WriterHelper) WriteDirectory(directory string, perm os.FileMode) error
 	return nil
 }
 
+// WriteFile writes a regular file with the given string content to the archive.
 func (w *WriterHelper) WriteFile(file, content string, perm os.FileMode) error {
 	return w.WriteFileRaw(file, []byte(content), perm)
 }
 
+// WriteFileRaw writes a regular file with the given byte content to the archive.
 func (w *WriterHelper) WriteFileRaw(file string, bytes []byte, perm os.FileMode) error {
 	err := w.ensureBaseDirectory(path.Dir(file))
 	if err != nil {
@@ -122,6 +133,7 @@ func (w *WriterHelper) WriteFileRaw(file string, bytes []byte, perm os.FileMode)
 	return nil
 }
 
+// WriteSymlinks writes multiple symbolic link entries to the archive.
 func (w *WriterHelper) WriteSymlinks(links []WriteSymlink) error {
 	for _, l := range links {
 		err := w.WriteSymlink(l.Target, l.Link, l.Perm)
@@ -132,6 +144,7 @@ func (w *WriterHelper) WriteSymlinks(links []WriteSymlink) error {
 	return nil
 }
 
+// WriteSymlink writes a single symbolic link entry to the archive.
 func (w *WriterHelper) WriteSymlink(target, link string, perm os.FileMode) error {
 	err := w.ensureBaseDirectory(path.Dir(link))
 	if err != nil {
@@ -159,6 +172,7 @@ func (w *WriterHelper) WriteSymlink(target, link string, perm os.FileMode) error
 	return nil
 }
 
+// WriteCharDevice writes a character device entry to the archive.
 func (w *WriterHelper) WriteCharDevice(device string, major, minor int64, perm os.FileMode) error {
 	err := w.ensureBaseDirectory(path.Dir(device))
 	if err != nil {
@@ -179,16 +193,18 @@ func (w *WriterHelper) WriteCharDevice(device string, major, minor int64, perm o
 	return nil
 }
 
+// CopyTree recursively copies a host directory tree into the archive.
 func (w *WriterHelper) CopyTree(path string) error {
 	walker := func(p string, info os.FileInfo, err error) error {
 		if err != nil {
 			return fmt.Errorf("error visiting %s: %w", p, err)
 		}
-		if info.Mode().IsDir() {
+		switch {
+		case info.Mode().IsDir():
 			err = w.WriteDirectory(p, info.Mode() & ^os.ModeType)
-		} else if info.Mode().IsRegular() {
+		case info.Mode().IsRegular():
 			err = w.CopyFile(p)
-		} else {
+		default:
 			err = fmt.Errorf("file type not handled for %s", p)
 		}
 
@@ -202,6 +218,7 @@ func (w *WriterHelper) CopyTree(path string) error {
 	return nil
 }
 
+// CopyFileTo copies a file from src on the host into the archive at dst.
 func (w *WriterHelper) CopyFileTo(src, dst string) (err error) {
 	if err := w.ensureBaseDirectory(path.Dir(dst)); err != nil {
 		return err
@@ -242,6 +259,7 @@ func (w *WriterHelper) CopyFileTo(src, dst string) (err error) {
 	return nil
 }
 
+// TransformFileTo reads src from the host, transforms it with fn, and writes the result into the archive at dst.
 func (w *WriterHelper) TransformFileTo(src, dst string, fn Transformer) (err error) {
 	if err := w.ensureBaseDirectory(path.Dir(dst)); err != nil {
 		return err
@@ -287,6 +305,7 @@ func (w *WriterHelper) TransformFileTo(src, dst string, fn Transformer) (err err
 	return nil
 }
 
+// CopyFile copies a file from the host into the archive at the same path.
 func (w *WriterHelper) CopyFile(in string) error {
 	return w.CopyFileTo(in, in)
 }

decompressors.go

@@ -10,6 +10,7 @@ import (
 	"github.com/ulikunitz/xz"
 )
 
+// ZstdDecompressor decompresses zstd-compressed data from src into dst.
 func ZstdDecompressor(dst io.Writer, src io.Reader) error {
 	decompressor, err := zstd.NewReader(src)
 	if err != nil {
@@ -24,13 +25,14 @@ func ZstdDecompressor(dst io.Writer, src io.Reader) error {
 	return nil
 }
 
+// XzDecompressor decompresses xz-compressed data from src into dst.
 func XzDecompressor(dst io.Writer, src io.Reader) error {
 	decompressor, err := xz.NewReader(src)
 	if err != nil {
 		return fmt.Errorf("failed to create xz decompressor: %w", err)
 	}
 	// There is no Close() API. See: https://github.com/ulikunitz/xz/issues/45
-	//defer decompressor.Close()
+	// defer decompressor.Close()
 
 	_, err = io.Copy(dst, decompressor)
 	if err != nil {
@@ -39,6 +41,7 @@ func XzDecompressor(dst io.Writer, src io.Reader) error {
 	return nil
 }
 
+// GzipDecompressor decompresses gzip-compressed data from src into dst.
 func GzipDecompressor(dst io.Writer, src io.Reader) (err error) {
 	decompressor, err := gzip.NewReader(src)
 	if err != nil {
@@ -57,6 +60,7 @@ func GzipDecompressor(dst io.Writer, src io.Reader) (err error) {
 	return nil
 }
 
+// NullDecompressor copies uncompressed data from src into dst unchanged.
 func NullDecompressor(dst io.Writer, src io.Reader) error {
 	_, err := io.Copy(dst, src)
 	if err != nil {

decompressors_test.go

@@ -10,7 +10,7 @@ import (
 	"path"
 	"testing"
 
-	"github.com/go-debos/fakemachine/cpio"
+	writerhelper "github.com/go-debos/fakemachine/cpio"
 	"github.com/stretchr/testify/require"
 )
 
@@ -50,8 +50,8 @@ func checkStreamsMatch(output, check io.Reader) error {
 	}
 }
 
-func decompressorTest(file, suffix string, d writerhelper.Transformer) (err error) {
-	testFilePath := path.Join("testdata", file+suffix)
+func decompressorTest(suffix string, d writerhelper.Transformer) (err error) {
+	testFilePath := path.Join("testdata", "test"+suffix)
 	f, err := os.Open(testFilePath)
 	if err != nil {
 		return fmt.Errorf("open test file %s: %w", testFilePath, err)
@@ -67,7 +67,7 @@ func decompressorTest(file, suffix string, d writerhelper.Transformer) (err erro
 		return fmt.Errorf("decompress test file %s: %w", testFilePath, err)
 	}
 
-	checkFilePath := path.Join("testdata", file)
+	checkFilePath := path.Join("testdata", "test")
 	checkFile, err := os.Open(checkFilePath)
 	if err != nil {
 		return fmt.Errorf("open check file %s: %w", checkFilePath, err)
@@ -86,21 +86,21 @@ func decompressorTest(file, suffix string, d writerhelper.Transformer) (err erro
 }
 
 func TestZstd(t *testing.T) {
-	err := decompressorTest("test", ".zst", ZstdDecompressor)
+	err := decompressorTest(".zst", ZstdDecompressor)
 	require.NoError(t, err)
 }
 
 func TestXz(t *testing.T) {
-	err := decompressorTest("test", ".xz", XzDecompressor)
+	err := decompressorTest(".xz", XzDecompressor)
 	require.NoError(t, err)
 }
 
 func TestGzip(t *testing.T) {
-	err := decompressorTest("test", ".gz", GzipDecompressor)
+	err := decompressorTest(".gz", GzipDecompressor)
 	require.NoError(t, err)
 }
 
 func TestNull(t *testing.T) {
-	err := decompressorTest("test", "", NullDecompressor)
+	err := decompressorTest("", NullDecompressor)
 	require.NoError(t, err)
 }