Source file src/pkg/cmd/gofmt/gofmt.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package main
     6	
     7	import (
     8		"bytes"
     9		"flag"
    10		"fmt"
    11		"go/ast"
    12		"go/parser"
    13		"go/printer"
    14		"go/scanner"
    15		"go/token"
    16		"io"
    17		"io/ioutil"
    18		"os"
    19		"os/exec"
    20		"path/filepath"
    21		"runtime"
    22		"runtime/pprof"
    23		"strings"
    24	)
    25	
    26	var (
    27		// main operation modes
    28		list        = flag.Bool("l", false, "list files whose formatting differs from gofmt's")
    29		write       = flag.Bool("w", false, "write result to (source) file instead of stdout")
    30		rewriteRule = flag.String("r", "", "rewrite rule (e.g., 'a[b:len(a)] -> a[b:]')")
    31		simplifyAST = flag.Bool("s", false, "simplify code")
    32		doDiff      = flag.Bool("d", false, "display diffs instead of rewriting files")
    33		allErrors   = flag.Bool("e", false, "report all errors (not just the first 10 on different lines)")
    34	
    35		// debugging
    36		cpuprofile = flag.String("cpuprofile", "", "write cpu profile to this file")
    37	)
    38	
    39	const (
    40		tabWidth    = 8
    41		printerMode = printer.UseSpaces | printer.TabIndent
    42	)
    43	
    44	var (
    45		fileSet    = token.NewFileSet() // per process FileSet
    46		exitCode   = 0
    47		rewrite    func(*ast.File) *ast.File
    48		parserMode parser.Mode
    49	)
    50	
    51	func report(err error) {
    52		scanner.PrintError(os.Stderr, err)
    53		exitCode = 2
    54	}
    55	
    56	func usage() {
    57		fmt.Fprintf(os.Stderr, "usage: gofmt [flags] [path ...]\n")
    58		flag.PrintDefaults()
    59	}
    60	
    61	func initParserMode() {
    62		parserMode = parser.ParseComments
    63		if *allErrors {
    64			parserMode |= parser.AllErrors
    65		}
    66	}
    67	
    68	func isGoFile(f os.FileInfo) bool {
    69		// ignore non-Go files
    70		name := f.Name()
    71		return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
    72	}
    73	
    74	// If in == nil, the source is the contents of the file with the given filename.
    75	func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error {
    76		var perm os.FileMode = 0644
    77		if in == nil {
    78			f, err := os.Open(filename)
    79			if err != nil {
    80				return err
    81			}
    82			defer f.Close()
    83			fi, err := f.Stat()
    84			if err != nil {
    85				return err
    86			}
    87			in = f
    88			perm = fi.Mode().Perm()
    89		}
    90	
    91		src, err := ioutil.ReadAll(in)
    92		if err != nil {
    93			return err
    94		}
    95	
    96		file, sourceAdj, indentAdj, err := parse(fileSet, filename, src, stdin)
    97		if err != nil {
    98			return err
    99		}
   100	
   101		if rewrite != nil {
   102			if sourceAdj == nil {
   103				file = rewrite(file)
   104			} else {
   105				fmt.Fprintf(os.Stderr, "warning: rewrite ignored for incomplete programs\n")
   106			}
   107		}
   108	
   109		ast.SortImports(fileSet, file)
   110	
   111		if *simplifyAST {
   112			simplify(file)
   113		}
   114	
   115		ast.Inspect(file, normalizeNumbers)
   116	
   117		res, err := format(fileSet, file, sourceAdj, indentAdj, src, printer.Config{Mode: printerMode, Tabwidth: tabWidth})
   118		if err != nil {
   119			return err
   120		}
   121	
   122		if !bytes.Equal(src, res) {
   123			// formatting has changed
   124			if *list {
   125				fmt.Fprintln(out, filename)
   126			}
   127			if *write {
   128				// make a temporary backup before overwriting original
   129				bakname, err := backupFile(filename+".", src, perm)
   130				if err != nil {
   131					return err
   132				}
   133				err = ioutil.WriteFile(filename, res, perm)
   134				if err != nil {
   135					os.Rename(bakname, filename)
   136					return err
   137				}
   138				err = os.Remove(bakname)
   139				if err != nil {
   140					return err
   141				}
   142			}
   143			if *doDiff {
   144				data, err := diff(src, res, filename)
   145				if err != nil {
   146					return fmt.Errorf("computing diff: %s", err)
   147				}
   148				fmt.Printf("diff -u %s %s\n", filepath.ToSlash(filename+".orig"), filepath.ToSlash(filename))
   149				out.Write(data)
   150			}
   151		}
   152	
   153		if !*list && !*write && !*doDiff {
   154			_, err = out.Write(res)
   155		}
   156	
   157		return err
   158	}
   159	
   160	func visitFile(path string, f os.FileInfo, err error) error {
   161		if err == nil && isGoFile(f) {
   162			err = processFile(path, nil, os.Stdout, false)
   163		}
   164		// Don't complain if a file was deleted in the meantime (i.e.
   165		// the directory changed concurrently while running gofmt).
   166		if err != nil && !os.IsNotExist(err) {
   167			report(err)
   168		}
   169		return nil
   170	}
   171	
   172	func walkDir(path string) {
   173		filepath.Walk(path, visitFile)
   174	}
   175	
   176	func main() {
   177		// call gofmtMain in a separate function
   178		// so that it can use defer and have them
   179		// run before the exit.
   180		gofmtMain()
   181		os.Exit(exitCode)
   182	}
   183	
   184	func gofmtMain() {
   185		flag.Usage = usage
   186		flag.Parse()
   187	
   188		if *cpuprofile != "" {
   189			f, err := os.Create(*cpuprofile)
   190			if err != nil {
   191				fmt.Fprintf(os.Stderr, "creating cpu profile: %s\n", err)
   192				exitCode = 2
   193				return
   194			}
   195			defer f.Close()
   196			pprof.StartCPUProfile(f)
   197			defer pprof.StopCPUProfile()
   198		}
   199	
   200		initParserMode()
   201		initRewrite()
   202	
   203		if flag.NArg() == 0 {
   204			if *write {
   205				fmt.Fprintln(os.Stderr, "error: cannot use -w with standard input")
   206				exitCode = 2
   207				return
   208			}
   209			if err := processFile("<standard input>", os.Stdin, os.Stdout, true); err != nil {
   210				report(err)
   211			}
   212			return
   213		}
   214	
   215		for i := 0; i < flag.NArg(); i++ {
   216			path := flag.Arg(i)
   217			switch dir, err := os.Stat(path); {
   218			case err != nil:
   219				report(err)
   220			case dir.IsDir():
   221				walkDir(path)
   222			default:
   223				if err := processFile(path, nil, os.Stdout, false); err != nil {
   224					report(err)
   225				}
   226			}
   227		}
   228	}
   229	
   230	func writeTempFile(dir, prefix string, data []byte) (string, error) {
   231		file, err := ioutil.TempFile(dir, prefix)
   232		if err != nil {
   233			return "", err
   234		}
   235		_, err = file.Write(data)
   236		if err1 := file.Close(); err == nil {
   237			err = err1
   238		}
   239		if err != nil {
   240			os.Remove(file.Name())
   241			return "", err
   242		}
   243		return file.Name(), nil
   244	}
   245	
   246	func diff(b1, b2 []byte, filename string) (data []byte, err error) {
   247		f1, err := writeTempFile("", "gofmt", b1)
   248		if err != nil {
   249			return
   250		}
   251		defer os.Remove(f1)
   252	
   253		f2, err := writeTempFile("", "gofmt", b2)
   254		if err != nil {
   255			return
   256		}
   257		defer os.Remove(f2)
   258	
   259		cmd := "diff"
   260		if runtime.GOOS == "plan9" {
   261			cmd = "/bin/ape/diff"
   262		}
   263	
   264		data, err = exec.Command(cmd, "-u", f1, f2).CombinedOutput()
   265		if len(data) > 0 {
   266			// diff exits with a non-zero status when the files don't match.
   267			// Ignore that failure as long as we get output.
   268			return replaceTempFilename(data, filename)
   269		}
   270		return
   271	}
   272	
   273	// replaceTempFilename replaces temporary filenames in diff with actual one.
   274	//
   275	// --- /tmp/gofmt316145376	2017-02-03 19:13:00.280468375 -0500
   276	// +++ /tmp/gofmt617882815	2017-02-03 19:13:00.280468375 -0500
   277	// ...
   278	// ->
   279	// --- path/to/file.go.orig	2017-02-03 19:13:00.280468375 -0500
   280	// +++ path/to/file.go	2017-02-03 19:13:00.280468375 -0500
   281	// ...
   282	func replaceTempFilename(diff []byte, filename string) ([]byte, error) {
   283		bs := bytes.SplitN(diff, []byte{'\n'}, 3)
   284		if len(bs) < 3 {
   285			return nil, fmt.Errorf("got unexpected diff for %s", filename)
   286		}
   287		// Preserve timestamps.
   288		var t0, t1 []byte
   289		if i := bytes.LastIndexByte(bs[0], '\t'); i != -1 {
   290			t0 = bs[0][i:]
   291		}
   292		if i := bytes.LastIndexByte(bs[1], '\t'); i != -1 {
   293			t1 = bs[1][i:]
   294		}
   295		// Always print filepath with slash separator.
   296		f := filepath.ToSlash(filename)
   297		bs[0] = []byte(fmt.Sprintf("--- %s%s", f+".orig", t0))
   298		bs[1] = []byte(fmt.Sprintf("+++ %s%s", f, t1))
   299		return bytes.Join(bs, []byte{'\n'}), nil
   300	}
   301	
   302	const chmodSupported = runtime.GOOS != "windows"
   303	
   304	// backupFile writes data to a new file named filename<number> with permissions perm,
   305	// with <number randomly chosen such that the file name is unique. backupFile returns
   306	// the chosen file name.
   307	func backupFile(filename string, data []byte, perm os.FileMode) (string, error) {
   308		// create backup file
   309		f, err := ioutil.TempFile(filepath.Dir(filename), filepath.Base(filename))
   310		if err != nil {
   311			return "", err
   312		}
   313		bakname := f.Name()
   314		if chmodSupported {
   315			err = f.Chmod(perm)
   316			if err != nil {
   317				f.Close()
   318				os.Remove(bakname)
   319				return bakname, err
   320			}
   321		}
   322	
   323		// write data to backup file
   324		_, err = f.Write(data)
   325		if err1 := f.Close(); err == nil {
   326			err = err1
   327		}
   328	
   329		return bakname, err
   330	}
   331	
   332	// normalizeNumbers rewrites base prefixes and exponents to
   333	// use lower-case letters, and removes leading 0's from
   334	// integer imaginary literals. It leaves hexadecimal digits
   335	// alone.
   336	func normalizeNumbers(n ast.Node) bool {
   337		lit, _ := n.(*ast.BasicLit)
   338		if lit == nil || (lit.Kind != token.INT && lit.Kind != token.FLOAT && lit.Kind != token.IMAG) {
   339			return true
   340		}
   341		if len(lit.Value) < 2 {
   342			return false // only one digit (common case) - nothing to do
   343		}
   344		// len(lit.Value) >= 2
   345	
   346		// We ignore lit.Kind because for lit.Kind == token.IMAG the literal may be an integer
   347		// or floating-point value, decimal or not. Instead, just consider the literal pattern.
   348		x := lit.Value
   349		switch x[:2] {
   350		default:
   351			// 0-prefix octal, decimal int, or float (possibly with 'i' suffix)
   352			if i := strings.LastIndexByte(x, 'E'); i >= 0 {
   353				x = x[:i] + "e" + x[i+1:]
   354				break
   355			}
   356			// remove leading 0's from integer (but not floating-point) imaginary literals
   357			if x[len(x)-1] == 'i' && strings.IndexByte(x, '.') < 0 && strings.IndexByte(x, 'e') < 0 {
   358				x = strings.TrimLeft(x, "0_")
   359				if x == "i" {
   360					x = "0i"
   361				}
   362			}
   363		case "0X":
   364			x = "0x" + x[2:]
   365			fallthrough
   366		case "0x":
   367			// possibly a hexadecimal float
   368			if i := strings.LastIndexByte(x, 'P'); i >= 0 {
   369				x = x[:i] + "p" + x[i+1:]
   370			}
   371		case "0O":
   372			x = "0o" + x[2:]
   373		case "0o":
   374			// nothing to do
   375		case "0B":
   376			x = "0b" + x[2:]
   377		case "0b":
   378			// nothing to do
   379		}
   380	
   381		lit.Value = x
   382		return false
   383	}
   384	

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