--- /dev/null
+// 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"
+ "io"
+ "go/ast"
+ "go/parser"
+ "go/token"
+ "os"
+ "strconv"
+ "strings"
+)
+
+var verbose = flag.Bool("v", false, "verbose")
+var printfuncs = flag.String("printfuncs", "", "comma-separated list of print function names to check")
+var exitCode = 0
+
+// 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 {
+ file *token.File
+}
+
+func main() {
+ flag.Usage = Usage
+ flag.Parse()
+
+ if *printfuncs != "" {
+ for _, name := range strings.Split(*printfuncs, ",", -1) {
+ if len(name) == 0 {
+ flag.Usage()
+ }
+ skip := 0
+ if colon := strings.LastIndex(name, ":"); colon > 0 {
+ var err os.Error
+ skip, err = strconv.Atoi(name[colon+1:])
+ if err != nil {
+ die(`illegal format for "Func:N" argument %q; %s`, name, err)
+ }
+ name = name[:colon]
+ }
+ if name[len(name)-1] == 'f' {
+ printfList[name] = skip
+ } else {
+ printList[name] = skip
+ }
+ }
+ }
+
+ if flag.NArg() == 0 {
+ doFile("stdin", os.Stdin)
+ } else {
+ for _, arg := range flag.Args() {
+ doFile(arg, 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) {
+ // TODO: process directories?
+ fs := token.NewFileSet()
+ parsedFile, err := parser.ParseFile(fs, name, reader, 0)
+ if err != nil {
+ die("%s: %s", name, err)
+ }
+ file := &File{fs.File(parsedFile.Pos())}
+ file.checkFile(name, parsedFile)
+}
+
+// die formats the error to standard error, adding program identification
+// and a newline, and exits the program.
+func die(format string, args ...interface{}) {
+ fmt.Fprintf(os.Stderr, "govet: "+format+"\n", args...)
+ os.Exit(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...)
+ exitCode = 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...)
+ exitCode = 1
+}
+
+// Warn reports an error but does not set the exit code.
+func (f *File) Warn(pos token.Pos, args ...interface{}) {
+ loc := f.file.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.file.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", name)
+ ast.Walk(f, file)
+}
+
+// Visit implements the ast.Visitor interface.
+func (f *File) Visit(node interface{}) ast.Visitor {
+ // TODO: could return nil for nodes that cannot contain a CallExpr -
+ // will shortcut traversal. Worthwhile?
+ switch n := node.(type) {
+ case *ast.CallExpr:
+ f.checkCallExpr(n)
+ }
+ return f
+}
+
+
+// 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.
+var printfList = map[string]int{
+ "Errorf": 0,
+ "Fatalf": 0,
+ "Fprintf": 1,
+ "Printf": 0,
+ "Sprintf": 0,
+}
+
+// printList records the unformatted-print functions. The value is the location
+// of the first parameter to be printed.
+var printList = map[string]int{
+ "Error": 0,
+ "Fatal": 0,
+ "Fprint": 1, "Fprintln": 1,
+ "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) {
+ 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 bytes.IndexByte(lit.Value, '%') < 0 {
+ 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.
+ numPercent := 0
+ for i := 0; i < len(lit.Value); i++ {
+ if lit.Value[i] == '%' {
+ if i+1 < len(lit.Value) && lit.Value[i+1] == '%' {
+ // %% doesn't count.
+ i++
+ } else {
+ numPercent++
+ }
+ }
+ }
+ expect := len(call.Args) - (skip + 1)
+ if numPercent != expect {
+ f.Badf(call.Pos(), "wrong number of formatting directives in %s call: %d percent(s) for %d args", name, numPercent, expect)
+ }
+}
+
+var terminalNewline = []byte(`\n"`) // \n at end of interpreted string
+
+// 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 bytes.IndexByte(lit.Value, '%') >= 0 {
+ 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 bytes.HasSuffix(lit.Value, terminalNewline) {
+ 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 govet --funcs="Bad:1,Badf:1,Warn:1,Warnf:1" govet.go
+func BadFunctionUsedInTests() {
+ fmt.Println() // niladic call
+ fmt.Println("%s", "hi") // % in call to Println
+ fmt.Printf("%s", "hi", 3) // wrong # percents
+ fmt.Printf("%s%%%d", "hi", 3) // right # percents
+ Printf("now is the time", "buddy") // no %s
+ f := new(File)
+ f.Warn(0, "%s", "hello", 3) // % in call to added function
+ f.Warnf(0, "%s", "hello", 3) // wrong # %s in call to added function
+}