Source file src/cmd/gofmt/gofmt.go

Documentation: cmd/gofmt

     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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