| // Copyright 2009 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. |
| |
| /* |
| Gofmt formats Go programs. |
| It uses tabs for indentation and blanks for alignment. |
| Alignment assumes that an editor is using a fixed-width font. |
| |
| Without an explicit path, it processes the standard input. Given a file, |
| it operates on that file; given a directory, it operates on all .go files in |
| that directory, recursively. (Files starting with a period are ignored.) |
| By default, gofmt prints the reformatted sources to standard output. |
| |
| Usage: |
| gofmt [flags] [path ...] |
| |
| The flags are: |
| -d |
| Do not print reformatted sources to standard output. |
| If a file's formatting is different than gofmt's, print diffs |
| to standard output. |
| -e |
| Print all (including spurious) errors. |
| -l |
| Do not print reformatted sources to standard output. |
| If a file's formatting is different from gofmt's, print its name |
| to standard output. |
| -G |
| Allow generic code, using type parameters. |
| See golang.org/issues/43651 for more information. |
| -r rule |
| Apply the rewrite rule to the source before reformatting. |
| -s |
| Try to simplify code (after applying the rewrite rule, if any). |
| -w |
| Do not print reformatted sources to standard output. |
| If a file's formatting is different from gofmt's, overwrite it |
| with gofmt's version. If an error occurred during overwriting, |
| the original file is restored from an automatic backup. |
| |
| Debugging support: |
| -cpuprofile filename |
| Write cpu profile to the specified file. |
| |
| |
| The rewrite rule specified with the -r flag must be a string of the form: |
| |
| pattern -> replacement |
| |
| Both pattern and replacement must be valid Go expressions. |
| In the pattern, single-character lowercase identifiers serve as |
| wildcards matching arbitrary sub-expressions; those expressions |
| will be substituted for the same identifiers in the replacement. |
| |
| When gofmt reads from standard input, it accepts either a full Go program |
| or a program fragment. A program fragment must be a syntactically |
| valid declaration list, statement list, or expression. When formatting |
| such a fragment, gofmt preserves leading indentation as well as leading |
| and trailing spaces, so that individual sections of a Go program can be |
| formatted by piping them through gofmt. |
| |
| Examples |
| |
| To check files for unnecessary parentheses: |
| |
| gofmt -r '(a) -> a' -l *.go |
| |
| To remove the parentheses: |
| |
| gofmt -r '(a) -> a' -w *.go |
| |
| To convert the package tree from explicit slice upper bounds to implicit ones: |
| |
| gofmt -r 'α[β:len(α)] -> α[β:]' -w $GOROOT/src |
| |
| The simplify command |
| |
| When invoked with -s gofmt will make the following source transformations where possible. |
| |
| An array, slice, or map composite literal of the form: |
| []T{T{}, T{}} |
| will be simplified to: |
| []T{{}, {}} |
| |
| A slice expression of the form: |
| s[a:len(s)] |
| will be simplified to: |
| s[a:] |
| |
| A range of the form: |
| for x, _ = range v {...} |
| will be simplified to: |
| for x = range v {...} |
| |
| A range of the form: |
| for _ = range v {...} |
| will be simplified to: |
| for range v {...} |
| |
| This may result in changes that are incompatible with earlier versions of Go. |
| */ |
| package main |
| |
| // BUG(rsc): The implementation of -r is a bit slow. |
| // BUG(gri): If -w fails, the restored original file may not have some of the |
| // original file attributes. |