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/fs" 16 "os" 17 "path/filepath" 18 "strings" 19 ) 20 21 // If src != nil, readSource converts src to a []byte if possible; 22 // otherwise it returns an error. If src == nil, readSource returns 23 // the result of reading the file specified by filename. 24 func readSource(filename string, src any) ([]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 return io.ReadAll(s) 38 } 39 return nil, errors.New("invalid source") 40 } 41 return os.ReadFile(filename) 42 } 43 44 // A Mode value is a set of flags (or 0). 45 // They control the amount of source code parsed and other optional 46 // parser functionality. 47 type Mode uint 48 49 const ( 50 PackageClauseOnly Mode = 1 << iota // stop parsing after package clause 51 ImportsOnly // stop parsing after import declarations 52 ParseComments // parse comments and add them to AST 53 Trace // print a trace of parsed productions 54 DeclarationErrors // report declaration errors 55 SpuriousErrors // same as AllErrors, for backward-compatibility 56 SkipObjectResolution // don't resolve identifiers to objects - see ParseFile 57 AllErrors = SpuriousErrors // report all errors (not just the first 10 on different lines) 58 ) 59 60 // ParseFile parses the source code of a single Go source file and returns 61 // the corresponding ast.File node. The source code may be provided via 62 // the filename of the source file, or via the src parameter. 63 // 64 // If src != nil, ParseFile parses the source from src and the filename is 65 // only used when recording position information. The type of the argument 66 // for the src parameter must be string, []byte, or io.Reader. 67 // If src == nil, ParseFile parses the file specified by filename. 68 // 69 // The mode parameter controls the amount of source text parsed and other 70 // optional parser functionality. If the SkipObjectResolution mode bit is set, 71 // the object resolution phase of parsing will be skipped, causing File.Scope, 72 // File.Unresolved, and all Ident.Obj fields to be nil. 73 // 74 // Position information is recorded in the file set fset, which must not be 75 // nil. 76 // 77 // If the source couldn't be read, the returned AST is nil and the error 78 // indicates the specific failure. If the source was read but syntax 79 // errors were found, the result is a partial AST (with ast.Bad* nodes 80 // representing the fragments of erroneous source code). Multiple errors 81 // are returned via a scanner.ErrorList which is sorted by source position. 82 func ParseFile(fset *token.FileSet, filename string, src any, mode Mode) (f *ast.File, err error) { 83 if fset == nil { 84 panic("parser.ParseFile: no token.FileSet provided (fset == nil)") 85 } 86 87 // get source 88 text, err := readSource(filename, src) 89 if err != nil { 90 return nil, err 91 } 92 93 var p parser 94 defer func() { 95 if e := recover(); e != nil { 96 // resume same panic if it's not a bailout 97 bail, ok := e.(bailout) 98 if !ok { 99 panic(e) 100 } else if bail.msg != "" { 101 p.errors.Add(p.file.Position(bail.pos), bail.msg) 102 } 103 } 104 105 // set result values 106 if f == nil { 107 // source is not a valid Go source file - satisfy 108 // ParseFile API and return a valid (but) empty 109 // *ast.File 110 f = &ast.File{ 111 Name: new(ast.Ident), 112 Scope: ast.NewScope(nil), 113 } 114 } 115 116 p.errors.Sort() 117 err = p.errors.Err() 118 }() 119 120 // parse source 121 p.init(fset, filename, text, mode) 122 f = p.parseFile() 123 124 return 125 } 126 127 // ParseDir calls ParseFile for all files with names ending in ".go" in the 128 // directory specified by path and returns a map of package name -> package 129 // AST with all the packages found. 130 // 131 // If filter != nil, only the files with fs.FileInfo entries passing through 132 // the filter (and ending in ".go") are considered. The mode bits are passed 133 // to ParseFile unchanged. Position information is recorded in fset, which 134 // must not be nil. 135 // 136 // If the directory couldn't be read, a nil map and the respective error are 137 // returned. If a parse error occurred, a non-nil but incomplete map and the 138 // first error encountered are returned. 139 func ParseDir(fset *token.FileSet, path string, filter func(fs.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) { 140 list, err := os.ReadDir(path) 141 if err != nil { 142 return nil, err 143 } 144 145 pkgs = make(map[string]*ast.Package) 146 for _, d := range list { 147 if d.IsDir() || !strings.HasSuffix(d.Name(), ".go") { 148 continue 149 } 150 if filter != nil { 151 info, err := d.Info() 152 if err != nil { 153 return nil, err 154 } 155 if !filter(info) { 156 continue 157 } 158 } 159 filename := filepath.Join(path, d.Name()) 160 if src, err := ParseFile(fset, filename, nil, mode); err == nil { 161 name := src.Name.Name 162 pkg, found := pkgs[name] 163 if !found { 164 pkg = &ast.Package{ 165 Name: name, 166 Files: make(map[string]*ast.File), 167 } 168 pkgs[name] = pkg 169 } 170 pkg.Files[filename] = src 171 } else if first == nil { 172 first = err 173 } 174 } 175 176 return 177 } 178 179 // ParseExprFrom is a convenience function for parsing an expression. 180 // The arguments have the same meaning as for ParseFile, but the source must 181 // be a valid Go (type or value) expression. Specifically, fset must not 182 // be nil. 183 // 184 // If the source couldn't be read, the returned AST is nil and the error 185 // indicates the specific failure. If the source was read but syntax 186 // errors were found, the result is a partial AST (with ast.Bad* nodes 187 // representing the fragments of erroneous source code). Multiple errors 188 // are returned via a scanner.ErrorList which is sorted by source position. 189 func ParseExprFrom(fset *token.FileSet, filename string, src any, mode Mode) (expr ast.Expr, err error) { 190 if fset == nil { 191 panic("parser.ParseExprFrom: no token.FileSet provided (fset == nil)") 192 } 193 194 // get source 195 text, err := readSource(filename, src) 196 if err != nil { 197 return nil, err 198 } 199 200 var p parser 201 defer func() { 202 if e := recover(); e != nil { 203 // resume same panic if it's not a bailout 204 bail, ok := e.(bailout) 205 if !ok { 206 panic(e) 207 } else if bail.msg != "" { 208 p.errors.Add(p.file.Position(bail.pos), bail.msg) 209 } 210 } 211 p.errors.Sort() 212 err = p.errors.Err() 213 }() 214 215 // parse expr 216 p.init(fset, filename, text, mode) 217 expr = p.parseRhsOrType() 218 219 // If a semicolon was inserted, consume it; 220 // report an error if there's more tokens. 221 if p.tok == token.SEMICOLON && p.lit == "\n" { 222 p.next() 223 } 224 p.expect(token.EOF) 225 226 return 227 } 228 229 // ParseExpr is a convenience function for obtaining the AST of an expression x. 230 // The position information recorded in the AST is undefined. The filename used 231 // in error messages is the empty string. 232 // 233 // If syntax errors were found, the result is a partial AST (with ast.Bad* nodes 234 // representing the fragments of erroneous source code). Multiple errors are 235 // returned via a scanner.ErrorList which is sorted by source position. 236 func ParseExpr(x string) (ast.Expr, error) { 237 return ParseExprFrom(token.NewFileSet(), "", []byte(x), 0) 238 } 239