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Source file src/cmd/vet/main.go

Documentation: cmd/vet

  // Copyright 2010 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  // Vet is a simple checker for static errors in Go source code.
  // See doc.go for more information.
  package main
  import (
  // Important! If you add flags here, make sure to update cmd/go/internal/vet/vetflag.go.
  var (
  	verbose = flag.Bool("v", false, "verbose")
  	source  = flag.Bool("source", false, "import from source instead of compiled object files")
  	tags    = flag.String("tags", "", "space-separated list of build tags to apply when parsing")
  	tagList = []string{} // exploded version of tags flag; set in main
  	vcfg          vetConfig
  	mustTypecheck bool
  var exitCode = 0
  // "-all" flag enables all non-experimental checks
  var all = triStateFlag("all", unset, "enable all non-experimental checks")
  // Flags to control which individual checks to perform.
  var report = map[string]*triState{
  	// Only unusual checks are written here.
  	// Most checks that operate during the AST walk are added by register.
  	"asmdecl":   triStateFlag("asmdecl", unset, "check assembly against Go declarations"),
  	"buildtags": triStateFlag("buildtags", unset, "check that +build tags are valid"),
  // experimental records the flags enabling experimental features. These must be
  // requested explicitly; they are not enabled by -all.
  var experimental = map[string]bool{}
  // setTrueCount record how many flags are explicitly set to true.
  var setTrueCount int
  // dirsRun and filesRun indicate whether the vet is applied to directory or
  // file targets. The distinction affects which checks are run.
  var dirsRun, filesRun bool
  // includesNonTest indicates whether the vet is applied to non-test targets.
  // Certain checks are relevant only if they touch both test and non-test files.
  var includesNonTest bool
  // A triState is a boolean that knows whether it has been set to either true or false.
  // It is used to identify if a flag appears; the standard boolean flag cannot
  // distinguish missing from unset. It also satisfies flag.Value.
  type triState int
  const (
  	unset triState = iota
  func triStateFlag(name string, value triState, usage string) *triState {
  	flag.Var(&value, name, usage)
  	return &value
  // triState implements flag.Value, flag.Getter, and flag.boolFlag.
  // They work like boolean flags: we can say vet -printf as well as vet -printf=true
  func (ts *triState) Get() interface{} {
  	return *ts == setTrue
  func (ts triState) isTrue() bool {
  	return ts == setTrue
  func (ts *triState) Set(value string) error {
  	b, err := strconv.ParseBool(value)
  	if err != nil {
  		return err
  	if b {
  		*ts = setTrue
  	} else {
  		*ts = setFalse
  	return nil
  func (ts *triState) String() string {
  	switch *ts {
  	case unset:
  		return "true" // An unset flag will be set by -all, so defaults to true.
  	case setTrue:
  		return "true"
  	case setFalse:
  		return "false"
  	panic("not reached")
  func (ts triState) IsBoolFlag() bool {
  	return true
  // vet tells whether to report errors for the named check, a flag name.
  func vet(name string) bool {
  	return report[name].isTrue()
  // setExit sets the value for os.Exit when it is called, later. It
  // remembers the highest value.
  func setExit(err int) {
  	if err > exitCode {
  		exitCode = err
  var (
  	// Each of these vars has a corresponding case in (*File).Visit.
  	assignStmt    *ast.AssignStmt
  	binaryExpr    *ast.BinaryExpr
  	callExpr      *ast.CallExpr
  	compositeLit  *ast.CompositeLit
  	exprStmt      *ast.ExprStmt
  	forStmt       *ast.ForStmt
  	funcDecl      *ast.FuncDecl
  	funcLit       *ast.FuncLit
  	genDecl       *ast.GenDecl
  	interfaceType *ast.InterfaceType
  	rangeStmt     *ast.RangeStmt
  	returnStmt    *ast.ReturnStmt
  	structType    *ast.StructType
  	// checkers is a two-level map.
  	// The outer level is keyed by a nil pointer, one of the AST vars above.
  	// The inner level is keyed by checker name.
  	checkers = make(map[ast.Node]map[string]func(*File, ast.Node))
  func register(name, usage string, fn func(*File, ast.Node), types ...ast.Node) {
  	report[name] = triStateFlag(name, unset, usage)
  	for _, typ := range types {
  		m := checkers[typ]
  		if m == nil {
  			m = make(map[string]func(*File, ast.Node))
  			checkers[typ] = m
  		m[name] = fn
  // Usage is a replacement usage function for the flags package.
  func Usage() {
  	fmt.Fprintf(os.Stderr, "Usage of vet:\n")
  	fmt.Fprintf(os.Stderr, "\tvet [flags] directory...\n")
  	fmt.Fprintf(os.Stderr, "\tvet [flags] files... # Must be a single package\n")
  	fmt.Fprintf(os.Stderr, "By default, -all is set and all non-experimental checks are run.\n")
  	fmt.Fprintf(os.Stderr, "For more information run\n")
  	fmt.Fprintf(os.Stderr, "\tgo doc cmd/vet\n\n")
  	fmt.Fprintf(os.Stderr, "Flags:\n")
  // File is a wrapper for the state of a file used in the parser.
  // The parse tree walkers are all methods of this type.
  type File struct {
  	pkg     *Package
  	fset    *token.FileSet
  	name    string
  	content []byte
  	file    *ast.File
  	b       bytes.Buffer // for use by methods
  	// Parsed package "foo" when checking package "foo_test"
  	basePkg *Package
  	// The keys are the objects that are receivers of a "String()
  	// string" method. The value reports whether the method has a
  	// pointer receiver.
  	// This is used by the recursiveStringer method in print.go.
  	stringerPtrs map[*ast.Object]bool
  	// Registered checkers to run.
  	checkers map[ast.Node][]func(*File, ast.Node)
  	// Unreachable nodes; can be ignored in shift check.
  	dead map[ast.Node]bool
  func main() {
  	flag.Usage = Usage
  	// If any flag is set, we run only those checks requested.
  	// If all flag is set true or if no flags are set true, set all the non-experimental ones
  	// not explicitly set (in effect, set the "-all" flag).
  	if setTrueCount == 0 || *all == setTrue {
  		for name, setting := range report {
  			if *setting == unset && !experimental[name] {
  				*setting = setTrue
  	// Accept space-separated tags because that matches
  	// the go command's other subcommands.
  	// Accept commas because go tool vet traditionally has.
  	tagList = strings.Fields(strings.Replace(*tags, ",", " ", -1))
  	if flag.NArg() == 0 {
  	// Special case for "go vet" passing an explicit configuration:
  	// single argument ending in vet.cfg.
  	// Once we have a more general mechanism for obtaining this
  	// information from build tools like the go command,
  	// vet should be changed to use it. This vet.cfg hack is an
  	// experiment to learn about what form that information should take.
  	if flag.NArg() == 1 && strings.HasSuffix(flag.Arg(0), "vet.cfg") {
  	for _, name := range flag.Args() {
  		// Is it a directory?
  		fi, err := os.Stat(name)
  		if err != nil {
  			warnf("error walking tree: %s", err)
  		if fi.IsDir() {
  			dirsRun = true
  		} else {
  			filesRun = true
  			if !strings.HasSuffix(name, "_test.go") {
  				includesNonTest = true
  	if dirsRun && filesRun {
  	if dirsRun {
  		for _, name := range flag.Args() {
  	if doPackage(flag.Args(), nil) == nil {
  		warnf("no files checked")
  // prefixDirectory places the directory name on the beginning of each name in the list.
  func prefixDirectory(directory string, names []string) {
  	if directory != "." {
  		for i, name := range names {
  			names[i] = filepath.Join(directory, name)
  // vetConfig is the JSON config struct prepared by the Go command.
  type vetConfig struct {
  	Compiler    string
  	Dir         string
  	ImportPath  string
  	GoFiles     []string
  	ImportMap   map[string]string
  	PackageFile map[string]string
  	SucceedOnTypecheckFailure bool
  	imp types.Importer
  func (v *vetConfig) Import(path string) (*types.Package, error) {
  	if v.imp == nil {
  		v.imp = importer.For(v.Compiler, v.openPackageFile)
  	if path == "unsafe" {
  		return v.imp.Import("unsafe")
  	p := v.ImportMap[path]
  	if p == "" {
  		return nil, fmt.Errorf("unknown import path %q", path)
  	if v.PackageFile[p] == "" {
  		return nil, fmt.Errorf("unknown package file for import %q", path)
  	return v.imp.Import(p)
  func (v *vetConfig) openPackageFile(path string) (io.ReadCloser, error) {
  	file := v.PackageFile[path]
  	if file == "" {
  		// Note that path here has been translated via v.ImportMap,
  		// unlike in the error in Import above. We prefer the error in
  		// Import, but it's worth diagnosing this one too, just in case.
  		return nil, fmt.Errorf("unknown package file for %q", path)
  	f, err := os.Open(file)
  	if err != nil {
  		return nil, err
  	return f, nil
  // doPackageCfg analyzes a single package described in a config file.
  func doPackageCfg(cfgFile string) {
  	js, err := ioutil.ReadFile(cfgFile)
  	if err != nil {
  		errorf("%v", err)
  	if err := json.Unmarshal(js, &vcfg); err != nil {
  		errorf("parsing vet config %s: %v", cfgFile, err)
  	stdImporter = &vcfg
  	mustTypecheck = true
  	doPackage(vcfg.GoFiles, nil)
  // doPackageDir analyzes the single package found in the directory, if there is one,
  // plus a test package, if there is one.
  func doPackageDir(directory string) {
  	context := build.Default
  	if len(context.BuildTags) != 0 {
  		warnf("build tags %s previously set", context.BuildTags)
  	context.BuildTags = append(tagList, context.BuildTags...)
  	pkg, err := context.ImportDir(directory, 0)
  	if err != nil {
  		// If it's just that there are no go source files, that's fine.
  		if _, nogo := err.(*build.NoGoError); nogo {
  		// Non-fatal: we are doing a recursive walk and there may be other directories.
  		warnf("cannot process directory %s: %s", directory, err)
  	var names []string
  	names = append(names, pkg.GoFiles...)
  	names = append(names, pkg.CgoFiles...)
  	names = append(names, pkg.TestGoFiles...) // These are also in the "foo" package.
  	names = append(names, pkg.SFiles...)
  	prefixDirectory(directory, names)
  	basePkg := doPackage(names, nil)
  	// Is there also a "foo_test" package? If so, do that one as well.
  	if len(pkg.XTestGoFiles) > 0 {
  		names = pkg.XTestGoFiles
  		prefixDirectory(directory, names)
  		doPackage(names, basePkg)
  type Package struct {
  	path      string
  	defs      map[*ast.Ident]types.Object
  	uses      map[*ast.Ident]types.Object
  	selectors map[*ast.SelectorExpr]*types.Selection
  	types     map[ast.Expr]types.TypeAndValue
  	spans     map[types.Object]Span
  	files     []*File
  	typesPkg  *types.Package
  // doPackage analyzes the single package constructed from the named files.
  // It returns the parsed Package or nil if none of the files have been checked.
  func doPackage(names []string, basePkg *Package) *Package {
  	var files []*File
  	var astFiles []*ast.File
  	fs := token.NewFileSet()
  	for _, name := range names {
  		data, err := ioutil.ReadFile(name)
  		if err != nil {
  			// Warn but continue to next package.
  			warnf("%s: %s", name, err)
  			return nil
  		checkBuildTag(name, data)
  		var parsedFile *ast.File
  		if strings.HasSuffix(name, ".go") {
  			parsedFile, err = parser.ParseFile(fs, name, data, 0)
  			if err != nil {
  				warnf("%s: %s", name, err)
  				return nil
  			astFiles = append(astFiles, parsedFile)
  		files = append(files, &File{
  			fset:    fs,
  			content: data,
  			name:    name,
  			file:    parsedFile,
  			dead:    make(map[ast.Node]bool),
  	if len(astFiles) == 0 {
  		return nil
  	pkg := new(Package)
  	pkg.path = astFiles[0].Name.Name
  	pkg.files = files
  	// Type check the package.
  	errs := pkg.check(fs, astFiles)
  	if errs != nil {
  		if vcfg.SucceedOnTypecheckFailure {
  		if *verbose || mustTypecheck {
  			for _, err := range errs {
  				fmt.Fprintf(os.Stderr, "%v\n", err)
  			if mustTypecheck {
  				// This message could be silenced, and we could just exit,
  				// but it might be helpful at least at first to make clear that the
  				// above errors are coming from vet and not the compiler
  				// (they often look like compiler errors, such as "declared but not used").
  				errorf("typecheck failures")
  	// Check.
  	chk := make(map[ast.Node][]func(*File, ast.Node))
  	for typ, set := range checkers {
  		for name, fn := range set {
  			if vet(name) {
  				chk[typ] = append(chk[typ], fn)
  	for _, file := range files {
  		file.pkg = pkg
  		file.basePkg = basePkg
  		file.checkers = chk
  		if file.file != nil {
  			file.walkFile(file.name, file.file)
  	return pkg
  func visit(path string, f os.FileInfo, err error) error {
  	if err != nil {
  		warnf("walk error: %s", err)
  		return err
  	// One package per directory. Ignore the files themselves.
  	if !f.IsDir() {
  		return nil
  	return nil
  func (pkg *Package) hasFileWithSuffix(suffix string) bool {
  	for _, f := range pkg.files {
  		if strings.HasSuffix(f.name, suffix) {
  			return true
  	return false
  // walkDir recursively walks the tree looking for Go packages.
  func walkDir(root string) {
  	filepath.Walk(root, visit)
  // errorf formats the error to standard error, adding program
  // identification and a newline, and exits.
  func errorf(format string, args ...interface{}) {
  	fmt.Fprintf(os.Stderr, "vet: "+format+"\n", args...)
  // warnf formats the error to standard error, adding program
  // identification and a newline, but does not exit.
  func warnf(format string, args ...interface{}) {
  	fmt.Fprintf(os.Stderr, "vet: "+format+"\n", args...)
  // Println is fmt.Println guarded by -v.
  func Println(args ...interface{}) {
  	if !*verbose {
  // Printf is fmt.Printf guarded by -v.
  func Printf(format string, args ...interface{}) {
  	if !*verbose {
  	fmt.Printf(format+"\n", args...)
  // Bad reports an error and sets the exit code..
  func (f *File) Bad(pos token.Pos, args ...interface{}) {
  	f.Warn(pos, args...)
  // Badf reports a formatted error and sets the exit code.
  func (f *File) Badf(pos token.Pos, format string, args ...interface{}) {
  	f.Warnf(pos, format, args...)
  // loc returns a formatted representation of the position.
  func (f *File) loc(pos token.Pos) string {
  	if pos == token.NoPos {
  		return ""
  	// Do not print columns. Because the pos often points to the start of an
  	// expression instead of the inner part with the actual error, the
  	// precision can mislead.
  	posn := f.fset.Position(pos)
  	return fmt.Sprintf("%s:%d", posn.Filename, posn.Line)
  // locPrefix returns a formatted representation of the position for use as a line prefix.
  func (f *File) locPrefix(pos token.Pos) string {
  	if pos == token.NoPos {
  		return ""
  	return fmt.Sprintf("%s: ", f.loc(pos))
  // Warn reports an error but does not set the exit code.
  func (f *File) Warn(pos token.Pos, args ...interface{}) {
  	fmt.Fprintf(os.Stderr, "%s%s", f.locPrefix(pos), fmt.Sprintln(args...))
  // Warnf reports a formatted error but does not set the exit code.
  func (f *File) Warnf(pos token.Pos, format string, args ...interface{}) {
  	fmt.Fprintf(os.Stderr, "%s%s\n", f.locPrefix(pos), fmt.Sprintf(format, args...))
  // walkFile walks the file's tree.
  func (f *File) walkFile(name string, file *ast.File) {
  	Println("Checking file", name)
  	ast.Walk(f, file)
  // Visit implements the ast.Visitor interface.
  func (f *File) Visit(node ast.Node) ast.Visitor {
  	var key ast.Node
  	switch node.(type) {
  	case *ast.AssignStmt:
  		key = assignStmt
  	case *ast.BinaryExpr:
  		key = binaryExpr
  	case *ast.CallExpr:
  		key = callExpr
  	case *ast.CompositeLit:
  		key = compositeLit
  	case *ast.ExprStmt:
  		key = exprStmt
  	case *ast.ForStmt:
  		key = forStmt
  	case *ast.FuncDecl:
  		key = funcDecl
  	case *ast.FuncLit:
  		key = funcLit
  	case *ast.GenDecl:
  		key = genDecl
  	case *ast.InterfaceType:
  		key = interfaceType
  	case *ast.RangeStmt:
  		key = rangeStmt
  	case *ast.ReturnStmt:
  		key = returnStmt
  	case *ast.StructType:
  		key = structType
  	for _, fn := range f.checkers[key] {
  		fn(f, node)
  	return f
  // gofmt returns a string representation of the expression.
  func (f *File) gofmt(x ast.Expr) string {
  	printer.Fprint(&f.b, f.fset, x)
  	return f.b.String()

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