1 // Copyright 2015 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 // TODO(gri): This file and the file src/cmd/gofmt/internal.go are 6 // the same (but for this comment and the package name). Do not modify 7 // one without the other. Determine if we can factor out functionality 8 // in a public API. See also #11844 for context. 9 10 package format 11 12 import ( 13 "bytes" 14 "go/ast" 15 "go/parser" 16 "go/printer" 17 "go/token" 18 "strings" 19 ) 20 21 // parse parses src, which was read from the named file, 22 // as a Go source file, declaration, or statement list. 23 func parse(fset *token.FileSet, filename string, src []byte, fragmentOk bool) ( 24 file *ast.File, 25 sourceAdj func(src []byte, indent int) []byte, 26 indentAdj int, 27 err error, 28 ) { 29 // Try as whole source file. 30 file, err = parser.ParseFile(fset, filename, src, parserMode) 31 // If there's no error, return. If the error is that the source file didn't begin with a 32 // package line and source fragments are ok, fall through to 33 // try as a source fragment. Stop and return on any other error. 34 if err == nil || !fragmentOk || !strings.Contains(err.Error(), "expected 'package'") { 35 return 36 } 37 38 // If this is a declaration list, make it a source file 39 // by inserting a package clause. 40 // Insert using a ';', not a newline, so that the line numbers 41 // in psrc match the ones in src. 42 psrc := append([]byte("package p;"), src...) 43 file, err = parser.ParseFile(fset, filename, psrc, parserMode) 44 if err == nil { 45 sourceAdj = func(src []byte, indent int) []byte { 46 // Remove the package clause. 47 // Gofmt has turned the ';' into a '\n'. 48 src = src[indent+len("package p\n"):] 49 return bytes.TrimSpace(src) 50 } 51 return 52 } 53 // If the error is that the source file didn't begin with a 54 // declaration, fall through to try as a statement list. 55 // Stop and return on any other error. 56 if !strings.Contains(err.Error(), "expected declaration") { 57 return 58 } 59 60 // If this is a statement list, make it a source file 61 // by inserting a package clause and turning the list 62 // into a function body. This handles expressions too. 63 // Insert using a ';', not a newline, so that the line numbers 64 // in fsrc match the ones in src. Add an extra '\n' before the '}' 65 // to make sure comments are flushed before the '}'. 66 fsrc := append(append([]byte("package p; func _() {"), src...), '\n', '\n', '}') 67 file, err = parser.ParseFile(fset, filename, fsrc, parserMode) 68 if err == nil { 69 sourceAdj = func(src []byte, indent int) []byte { 70 // Cap adjusted indent to zero. 71 if indent < 0 { 72 indent = 0 73 } 74 // Remove the wrapping. 75 // Gofmt has turned the ';' into a '\n'. 76 // There will be two non-blank lines with indent, hence 2*indent. 77 src = src[2*indent+len("package p\n\nfunc _() {"):] 78 // Remove only the "}\n" suffix: remaining whitespaces will be trimmed anyway 79 src = src[:len(src)-len("}\n")] 80 return bytes.TrimSpace(src) 81 } 82 // Gofmt has also indented the function body one level. 83 // Adjust that with indentAdj. 84 indentAdj = -1 85 } 86 87 // Succeeded, or out of options. 88 return 89 } 90 91 // format formats the given package file originally obtained from src 92 // and adjusts the result based on the original source via sourceAdj 93 // and indentAdj. 94 func format( 95 fset *token.FileSet, 96 file *ast.File, 97 sourceAdj func(src []byte, indent int) []byte, 98 indentAdj int, 99 src []byte, 100 cfg printer.Config, 101 ) ([]byte, error) { 102 if sourceAdj == nil { 103 // Complete source file. 104 var buf bytes.Buffer 105 err := cfg.Fprint(&buf, fset, file) 106 if err != nil { 107 return nil, err 108 } 109 return buf.Bytes(), nil 110 } 111 112 // Partial source file. 113 // Determine and prepend leading space. 114 i, j := 0, 0 115 for j < len(src) && isSpace(src[j]) { 116 if src[j] == '\n' { 117 i = j + 1 // byte offset of last line in leading space 118 } 119 j++ 120 } 121 var res []byte 122 res = append(res, src[:i]...) 123 124 // Determine and prepend indentation of first code line. 125 // Spaces are ignored unless there are no tabs, 126 // in which case spaces count as one tab. 127 indent := 0 128 hasSpace := false 129 for _, b := range src[i:j] { 130 switch b { 131 case ' ': 132 hasSpace = true 133 case '\t': 134 indent++ 135 } 136 } 137 if indent == 0 && hasSpace { 138 indent = 1 139 } 140 for i := 0; i < indent; i++ { 141 res = append(res, '\t') 142 } 143 144 // Format the source. 145 // Write it without any leading and trailing space. 146 cfg.Indent = indent + indentAdj 147 var buf bytes.Buffer 148 err := cfg.Fprint(&buf, fset, file) 149 if err != nil { 150 return nil, err 151 } 152 out := sourceAdj(buf.Bytes(), cfg.Indent) 153 154 // If the adjusted output is empty, the source 155 // was empty but (possibly) for white space. 156 // The result is the incoming source. 157 if len(out) == 0 { 158 return src, nil 159 } 160 161 // Otherwise, append output to leading space. 162 res = append(res, out...) 163 164 // Determine and append trailing space. 165 i = len(src) 166 for i > 0 && isSpace(src[i-1]) { 167 i-- 168 } 169 return append(res, src[i:]...), nil 170 } 171 172 // isSpace reports whether the byte is a space character. 173 // isSpace defines a space as being among the following bytes: ' ', '\t', '\n' and '\r'. 174 func isSpace(b byte) bool { 175 return b == ' ' || b == '\t' || b == '\n' || b == '\r' 176 } 177
