Source file src/pkg/go/parser/interface.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 // This file contains the exported entry points for invoking the parser. 6 7 package parser 8 9 import ( 10 "bytes" 11 "errors" 12 "go/ast" 13 "go/token" 14 "io" 15 "io/ioutil" 16 "os" 17 "path/filepath" 18 ) 19 20 // If src != nil, readSource converts src to a []byte if possible; 21 // otherwise it returns an error. If src == nil, readSource returns 22 // the result of reading the file specified by filename. 23 // 24 func readSource(filename string, src interface{}) ([]byte, error) { 25 if src != nil { 26 switch s := src.(type) { 27 case string: 28 return []byte(s), nil 29 case []byte: 30 return s, nil 31 case *bytes.Buffer: 32 // is io.Reader, but src is already available in []byte form 33 if s != nil { 34 return s.Bytes(), nil 35 } 36 case io.Reader: 37 var buf bytes.Buffer 38 if _, err := io.Copy(&buf, s); err != nil { 39 return nil, err 40 } 41 return buf.Bytes(), nil 42 } 43 return nil, errors.New("invalid source") 44 } 45 return ioutil.ReadFile(filename) 46 } 47 48 // A Mode value is a set of flags (or 0). 49 // They control the amount of source code parsed and other optional 50 // parser functionality. 51 // 52 type Mode uint 53 54 const ( 55 PackageClauseOnly Mode = 1 << iota // parsing stops after package clause 56 ImportsOnly // parsing stops after import declarations 57 ParseComments // parse comments and add them to AST 58 Trace // print a trace of parsed productions 59 DeclarationErrors // report declaration errors 60 SpuriousErrors // report all (not just the first) errors per line 61 ) 62 63 // ParseFile parses the source code of a single Go source file and returns 64 // the corresponding ast.File node. The source code may be provided via 65 // the filename of the source file, or via the src parameter. 66 // 67 // If src != nil, ParseFile parses the source from src and the filename is 68 // only used when recording position information. The type of the argument 69 // for the src parameter must be string, []byte, or io.Reader. 70 // If src == nil, ParseFile parses the file specified by filename. 71 // 72 // The mode parameter controls the amount of source text parsed and other 73 // optional parser functionality. Position information is recorded in the 74 // file set fset. 75 // 76 // If the source couldn't be read, the returned AST is nil and the error 77 // indicates the specific failure. If the source was read but syntax 78 // errors were found, the result is a partial AST (with ast.Bad* nodes 79 // representing the fragments of erroneous source code). Multiple errors 80 // are returned via a scanner.ErrorList which is sorted by file position. 81 // 82 func ParseFile(fset *token.FileSet, filename string, src interface{}, mode Mode) (*ast.File, error) { 83 // get source 84 text, err := readSource(filename, src) 85 if err != nil { 86 return nil, err 87 } 88 89 // parse source 90 var p parser 91 p.init(fset, filename, text, mode) 92 f := p.parseFile() 93 94 // sort errors 95 if p.mode&SpuriousErrors == 0 { 96 p.errors.RemoveMultiples() 97 } else { 98 p.errors.Sort() 99 } 100 101 return f, p.errors.Err() 102 } 103 104 // ParseDir calls ParseFile for the files in the directory specified by path and 105 // returns a map of package name -> package AST with all the packages found. If 106 // filter != nil, only the files with os.FileInfo entries passing through the filter 107 // are considered. The mode bits are passed to ParseFile unchanged. Position 108 // information is recorded in the file set fset. 109 // 110 // If the directory couldn't be read, a nil map and the respective error are 111 // returned. If a parse error occurred, a non-nil but incomplete map and the 112 // first error encountered are returned. 113 // 114 func ParseDir(fset *token.FileSet, path string, filter func(os.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) { 115 fd, err := os.Open(path) 116 if err != nil { 117 return nil, err 118 } 119 defer fd.Close() 120 121 list, err := fd.Readdir(-1) 122 if err != nil { 123 return nil, err 124 } 125 126 pkgs = make(map[string]*ast.Package) 127 for _, d := range list { 128 if filter == nil || filter(d) { 129 filename := filepath.Join(path, d.Name()) 130 if src, err := ParseFile(fset, filename, nil, mode); err == nil { 131 name := src.Name.Name 132 pkg, found := pkgs[name] 133 if !found { 134 pkg = &ast.Package{ 135 Name: name, 136 Files: make(map[string]*ast.File), 137 } 138 pkgs[name] = pkg 139 } 140 pkg.Files[filename] = src 141 } else if first == nil { 142 first = err 143 } 144 } 145 } 146 147 return 148 } 149 150 // ParseExpr is a convenience function for obtaining the AST of an expression x. 151 // The position information recorded in the AST is undefined. 152 // 153 func ParseExpr(x string) (ast.Expr, error) { 154 // parse x within the context of a complete package for correct scopes; 155 // use //line directive for correct positions in error messages and put 156 // x alone on a separate line (handles line comments), followed by a ';' 157 // to force an error if the expression is incomplete 158 file, err := ParseFile(token.NewFileSet(), "", "package p;func _(){_=\n//line :1\n"+x+"\n;}", 0) 159 if err != nil { 160 return nil, err 161 } 162 return file.Decls[0].(*ast.FuncDecl).Body.List[0].(*ast.AssignStmt).Rhs[0], nil 163 }