/src/cmd/govet/govet.go
Go | 573 lines | 429 code | 52 blank | 92 comment | 115 complexity | 27168f6ef8ae460af52f9e3d656ffbce MD5 | raw file
Possible License(s): BSD-3-Clause
- // 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.
- // Govet is a simple checker for static errors in Go source code.
- // See doc.go for more information.
- package main
- import (
- "bytes"
- "flag"
- "fmt"
- "go/ast"
- "go/parser"
- "go/printer"
- "go/token"
- "io"
- "os"
- "path/filepath"
- "reflect"
- "strconv"
- "strings"
- "unicode/utf8"
- )
- var verbose = flag.Bool("v", false, "verbose")
- var printfuncs = flag.String("printfuncs", "", "comma-separated list of print function names to check")
- var exitCode = 0
- // 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
- }
- }
- // Usage is a replacement usage function for the flags package.
- func Usage() {
- fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
- flag.PrintDefaults()
- os.Exit(2)
- }
- // 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 {
- fset *token.FileSet
- file *ast.File
- b bytes.Buffer // for use by methods
- }
- func main() {
- flag.Usage = Usage
- flag.Parse()
- if *printfuncs != "" {
- for _, name := range strings.Split(*printfuncs, ",") {
- if len(name) == 0 {
- flag.Usage()
- }
- skip := 0
- if colon := strings.LastIndex(name, ":"); colon > 0 {
- var err error
- skip, err = strconv.Atoi(name[colon+1:])
- if err != nil {
- errorf(`illegal format for "Func:N" argument %q; %s`, name, err)
- }
- name = name[:colon]
- }
- name = strings.ToLower(name)
- if name[len(name)-1] == 'f' {
- printfList[name] = skip
- } else {
- printList[name] = skip
- }
- }
- }
- if flag.NArg() == 0 {
- doFile("stdin", os.Stdin)
- } else {
- for _, name := range flag.Args() {
- // Is it a directory?
- if fi, err := os.Stat(name); err == nil && fi.IsDir() {
- walkDir(name)
- } else {
- doFile(name, nil)
- }
- }
- }
- os.Exit(exitCode)
- }
- // doFile analyzes one file. If the reader is nil, the source code is read from the
- // named file.
- func doFile(name string, reader io.Reader) {
- fs := token.NewFileSet()
- parsedFile, err := parser.ParseFile(fs, name, reader, 0)
- if err != nil {
- errorf("%s: %s", name, err)
- return
- }
- file := &File{fset: fs, file: parsedFile}
- file.checkFile(name, parsedFile)
- }
- func visit(path string, f os.FileInfo, err error) error {
- if err != nil {
- errorf("walk error: %s", err)
- return nil
- }
- if !f.IsDir() && strings.HasSuffix(path, ".go") {
- doFile(path, nil)
- }
- return nil
- }
- // walkDir recursively walks the tree looking for .go files.
- func walkDir(root string) {
- filepath.Walk(root, visit)
- }
- // error formats the error to standard error, adding program
- // identification and a newline
- func errorf(format string, args ...interface{}) {
- fmt.Fprintf(os.Stderr, "govet: "+format+"\n", args...)
- setExit(2)
- }
- // Println is fmt.Println guarded by -v.
- func Println(args ...interface{}) {
- if !*verbose {
- return
- }
- fmt.Println(args...)
- }
- // Printf is fmt.Printf guarded by -v.
- func Printf(format string, args ...interface{}) {
- if !*verbose {
- return
- }
- 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...)
- setExit(1)
- }
- // 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...)
- setExit(1)
- }
- // Warn reports an error but does not set the exit code.
- func (f *File) Warn(pos token.Pos, args ...interface{}) {
- loc := f.fset.Position(pos).String() + ": "
- fmt.Fprint(os.Stderr, loc+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{}) {
- loc := f.fset.Position(pos).String() + ": "
- fmt.Fprintf(os.Stderr, loc+format+"\n", args...)
- }
- // checkFile checks all the top-level declarations in a file.
- func (f *File) checkFile(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 {
- switch n := node.(type) {
- case *ast.CallExpr:
- f.checkCallExpr(n)
- case *ast.Field:
- f.checkFieldTag(n)
- case *ast.FuncDecl:
- f.checkMethodDecl(n)
- case *ast.InterfaceType:
- f.checkInterfaceType(n)
- }
- return f
- }
- // checkMethodDecl checks for canonical method signatures
- // in method declarations.
- func (f *File) checkMethodDecl(d *ast.FuncDecl) {
- if d.Recv == nil {
- // not a method
- return
- }
- f.checkMethod(d.Name, d.Type)
- }
- // checkInterfaceType checks for canonical method signatures
- // in interface definitions.
- func (f *File) checkInterfaceType(t *ast.InterfaceType) {
- for _, field := range t.Methods.List {
- for _, id := range field.Names {
- f.checkMethod(id, field.Type.(*ast.FuncType))
- }
- }
- }
- type MethodSig struct {
- args []string
- results []string
- }
- // canonicalMethods lists the input and output types for Go methods
- // that are checked using dynamic interface checks. Because the
- // checks are dynamic, such methods would not cause a compile error
- // if they have the wrong signature: instead the dynamic check would
- // fail, sometimes mysteriously. If a method is found with a name listed
- // here but not the input/output types listed here, govet complains.
- //
- // A few of the canonical methods have very common names.
- // For example, a type might implement a Scan method that
- // has nothing to do with fmt.Scanner, but we still want to check
- // the methods that are intended to implement fmt.Scanner.
- // To do that, the arguments that have a + prefix are treated as
- // signals that the canonical meaning is intended: if a Scan
- // method doesn't have a fmt.ScanState as its first argument,
- // we let it go. But if it does have a fmt.ScanState, then the
- // rest has to match.
- var canonicalMethods = map[string]MethodSig{
- // "Flush": {{}, {"error"}}, // http.Flusher and jpeg.writer conflict
- "Format": {[]string{"=fmt.State", "rune"}, []string{}}, // fmt.Formatter
- "GobDecode": {[]string{"[]byte"}, []string{"error"}}, // gob.GobDecoder
- "GobEncode": {[]string{}, []string{"[]byte", "error"}}, // gob.GobEncoder
- "MarshalJSON": {[]string{}, []string{"[]byte", "error"}}, // json.Marshaler
- "MarshalXML": {[]string{}, []string{"[]byte", "error"}}, // xml.Marshaler
- "Peek": {[]string{"=int"}, []string{"[]byte", "error"}}, // image.reader (matching bufio.Reader)
- "ReadByte": {[]string{}, []string{"byte", "error"}}, // io.ByteReader
- "ReadFrom": {[]string{"=io.Reader"}, []string{"int64", "error"}}, // io.ReaderFrom
- "ReadRune": {[]string{}, []string{"rune", "int", "error"}}, // io.RuneReader
- "Scan": {[]string{"=fmt.ScanState", "rune"}, []string{"error"}}, // fmt.Scanner
- "Seek": {[]string{"=int64", "int"}, []string{"int64", "error"}}, // io.Seeker
- "UnmarshalJSON": {[]string{"[]byte"}, []string{"error"}}, // json.Unmarshaler
- "UnreadByte": {[]string{}, []string{"error"}},
- "UnreadRune": {[]string{}, []string{"error"}},
- "WriteByte": {[]string{"byte"}, []string{"error"}}, // jpeg.writer (matching bufio.Writer)
- "WriteTo": {[]string{"=io.Writer"}, []string{"int64", "error"}}, // io.WriterTo
- }
- func (f *File) checkMethod(id *ast.Ident, t *ast.FuncType) {
- // Expected input/output.
- expect, ok := canonicalMethods[id.Name]
- if !ok {
- return
- }
- // Actual input/output
- args := typeFlatten(t.Params.List)
- var results []ast.Expr
- if t.Results != nil {
- results = typeFlatten(t.Results.List)
- }
- // Do the =s (if any) all match?
- if !f.matchParams(expect.args, args, "=") || !f.matchParams(expect.results, results, "=") {
- return
- }
- // Everything must match.
- if !f.matchParams(expect.args, args, "") || !f.matchParams(expect.results, results, "") {
- expectFmt := id.Name + "(" + argjoin(expect.args) + ")"
- if len(expect.results) == 1 {
- expectFmt += " " + argjoin(expect.results)
- } else if len(expect.results) > 1 {
- expectFmt += " (" + argjoin(expect.results) + ")"
- }
- f.b.Reset()
- if err := printer.Fprint(&f.b, f.fset, t); err != nil {
- fmt.Fprintf(&f.b, "<%s>", err)
- }
- actual := f.b.String()
- if strings.HasPrefix(actual, "func(") {
- actual = actual[4:]
- }
- actual = id.Name + actual
- f.Warnf(id.Pos(), "method %s should have signature %s", actual, expectFmt)
- }
- }
- func argjoin(x []string) string {
- y := make([]string, len(x))
- for i, s := range x {
- if s[0] == '=' {
- s = s[1:]
- }
- y[i] = s
- }
- return strings.Join(y, ", ")
- }
- // Turn parameter list into slice of types
- // (in the ast, types are Exprs).
- // Have to handle f(int, bool) and f(x, y, z int)
- // so not a simple 1-to-1 conversion.
- func typeFlatten(l []*ast.Field) []ast.Expr {
- var t []ast.Expr
- for _, f := range l {
- if len(f.Names) == 0 {
- t = append(t, f.Type)
- continue
- }
- for _ = range f.Names {
- t = append(t, f.Type)
- }
- }
- return t
- }
- // Does each type in expect with the given prefix match the corresponding type in actual?
- func (f *File) matchParams(expect []string, actual []ast.Expr, prefix string) bool {
- for i, x := range expect {
- if !strings.HasPrefix(x, prefix) {
- continue
- }
- if i >= len(actual) {
- return false
- }
- if !f.matchParamType(x, actual[i]) {
- return false
- }
- }
- if prefix == "" && len(actual) > len(expect) {
- return false
- }
- return true
- }
- // Does this one type match?
- func (f *File) matchParamType(expect string, actual ast.Expr) bool {
- if strings.HasPrefix(expect, "=") {
- expect = expect[1:]
- }
- // Strip package name if we're in that package.
- if n := len(f.file.Name.Name); len(expect) > n && expect[:n] == f.file.Name.Name && expect[n] == '.' {
- expect = expect[n+1:]
- }
- // Overkill but easy.
- f.b.Reset()
- printer.Fprint(&f.b, f.fset, actual)
- return f.b.String() == expect
- }
- // checkField checks a struct field tag.
- func (f *File) checkFieldTag(field *ast.Field) {
- if field.Tag == nil {
- return
- }
- tag, err := strconv.Unquote(field.Tag.Value)
- if err != nil {
- f.Warnf(field.Pos(), "unable to read struct tag %s", field.Tag.Value)
- return
- }
- // Check tag for validity by appending
- // new key:value to end and checking that
- // the tag parsing code can find it.
- if reflect.StructTag(tag+` _gofix:"_magic"`).Get("_gofix") != "_magic" {
- f.Warnf(field.Pos(), "struct field tag %s not compatible with reflect.StructTag.Get", field.Tag.Value)
- return
- }
- }
- // checkCallExpr checks a call expression.
- func (f *File) checkCallExpr(call *ast.CallExpr) {
- switch x := call.Fun.(type) {
- case *ast.Ident:
- f.checkCall(call, x.Name)
- case *ast.SelectorExpr:
- f.checkCall(call, x.Sel.Name)
- }
- }
- // printfList records the formatted-print functions. The value is the location
- // of the format parameter. Names are lower-cased so the lookup is
- // case insensitive.
- var printfList = map[string]int{
- "errorf": 0,
- "fatalf": 0,
- "fprintf": 1,
- "panicf": 0,
- "printf": 0,
- "sprintf": 0,
- }
- // printList records the unformatted-print functions. The value is the location
- // of the first parameter to be printed. Names are lower-cased so the lookup is
- // case insensitive.
- var printList = map[string]int{
- "error": 0,
- "fatal": 0,
- "fprint": 1, "fprintln": 1,
- "panic": 0, "panicln": 0,
- "print": 0, "println": 0,
- "sprint": 0, "sprintln": 0,
- }
- // checkCall triggers the print-specific checks if the call invokes a print function.
- func (f *File) checkCall(call *ast.CallExpr, Name string) {
- name := strings.ToLower(Name)
- if skip, ok := printfList[name]; ok {
- f.checkPrintf(call, Name, skip)
- return
- }
- if skip, ok := printList[name]; ok {
- f.checkPrint(call, Name, skip)
- return
- }
- }
- // checkPrintf checks a call to a formatted print routine such as Printf.
- // The skip argument records how many arguments to ignore; that is,
- // call.Args[skip] is (well, should be) the format argument.
- func (f *File) checkPrintf(call *ast.CallExpr, name string, skip int) {
- if len(call.Args) <= skip {
- return
- }
- // Common case: literal is first argument.
- arg := call.Args[skip]
- lit, ok := arg.(*ast.BasicLit)
- if !ok {
- // Too hard to check.
- if *verbose {
- f.Warn(call.Pos(), "can't check args for call to", name)
- }
- return
- }
- if lit.Kind == token.STRING {
- if !strings.Contains(lit.Value, "%") {
- if len(call.Args) > skip+1 {
- f.Badf(call.Pos(), "no formatting directive in %s call", name)
- }
- return
- }
- }
- // Hard part: check formats against args.
- // Trivial but useful test: count.
- numArgs := 0
- for i, w := 0, 0; i < len(lit.Value); i += w {
- w = 1
- if lit.Value[i] == '%' {
- nbytes, nargs := parsePrintfVerb(lit.Value[i:])
- w = nbytes
- numArgs += nargs
- }
- }
- expect := len(call.Args) - (skip + 1)
- if numArgs != expect {
- f.Badf(call.Pos(), "wrong number of args in %s call: %d needed but %d args", name, numArgs, expect)
- }
- }
- // parsePrintfVerb returns the number of bytes and number of arguments
- // consumed by the Printf directive that begins s, including its percent sign
- // and verb.
- func parsePrintfVerb(s string) (nbytes, nargs int) {
- // There's guaranteed a percent sign.
- nbytes = 1
- end := len(s)
- // There may be flags.
- FlagLoop:
- for nbytes < end {
- switch s[nbytes] {
- case '#', '0', '+', '-', ' ':
- nbytes++
- default:
- break FlagLoop
- }
- }
- getNum := func() {
- if nbytes < end && s[nbytes] == '*' {
- nbytes++
- nargs++
- } else {
- for nbytes < end && '0' <= s[nbytes] && s[nbytes] <= '9' {
- nbytes++
- }
- }
- }
- // There may be a width.
- getNum()
- // If there's a period, there may be a precision.
- if nbytes < end && s[nbytes] == '.' {
- nbytes++
- getNum()
- }
- // Now a verb.
- c, w := utf8.DecodeRuneInString(s[nbytes:])
- nbytes += w
- if c != '%' {
- nargs++
- }
- return
- }
- // checkPrint checks a call to an unformatted print routine such as Println.
- // The skip argument records how many arguments to ignore; that is,
- // call.Args[skip] is the first argument to be printed.
- func (f *File) checkPrint(call *ast.CallExpr, name string, skip int) {
- isLn := strings.HasSuffix(name, "ln")
- args := call.Args
- if len(args) <= skip {
- if *verbose && !isLn {
- f.Badf(call.Pos(), "no args in %s call", name)
- }
- return
- }
- arg := args[skip]
- if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
- if strings.Contains(lit.Value, "%") {
- f.Badf(call.Pos(), "possible formatting directive in %s call", name)
- }
- }
- if isLn {
- // The last item, if a string, should not have a newline.
- arg = args[len(call.Args)-1]
- if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
- if strings.HasSuffix(lit.Value, `\n"`) {
- f.Badf(call.Pos(), "%s call ends with newline", name)
- }
- }
- }
- }
- // This function never executes, but it serves as a simple test for the program.
- // Test with make test.
- func BadFunctionUsedInTests() {
- fmt.Println() // not an error
- fmt.Println("%s", "hi") // ERROR "possible formatting directive in Println call"
- fmt.Printf("%s", "hi", 3) // ERROR "wrong number of args in Printf call"
- fmt.Printf("%s%%%d", "hi", 3) // correct
- fmt.Printf("%.*d", 3, 3) // correct
- fmt.Printf("%.*d", 3, 3, 3) // ERROR "wrong number of args in Printf call"
- printf("now is the time", "buddy") // ERROR "no formatting directive"
- Printf("now is the time", "buddy") // ERROR "no formatting directive"
- Printf("hi") // ok
- f := new(File)
- f.Warn(0, "%s", "hello", 3) // ERROR "possible formatting directive in Warn call"
- f.Warnf(0, "%s", "hello", 3) // ERROR "wrong number of args in Warnf call"
- }
- type BadTypeUsedInTests struct {
- X int "hello" // ERROR "struct field tag"
- }
- func (t *BadTypeUsedInTests) Scan(x fmt.ScanState, c byte) { // ERROR "method Scan[(]x fmt.ScanState, c byte[)] should have signature Scan[(]fmt.ScanState, rune[)] error"
- }
- type BadInterfaceUsedInTests interface {
- ReadByte() byte // ERROR "method ReadByte[(][)] byte should have signature ReadByte[(][)] [(]byte, error[)]"
- }
- // printf is used by the test.
- func printf(format string, args ...interface{}) {
- panic("don't call - testing only")
- }