Source file src/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/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 // 25 func readSource(filename string, src any) ([]byte, error) { 26 if src != nil { 27 switch s := src.(type) { 28 case string: 29 return []byte(s), nil 30 case []byte: 31 return s, nil 32 case *bytes.Buffer: 33 // is io.Reader, but src is already available in []byte form 34 if s != nil { 35 return s.Bytes(), nil 36 } 37 case io.Reader: 38 return io.ReadAll(s) 39 } 40 return nil, errors.New("invalid source") 41 } 42 return os.ReadFile(filename) 43 } 44 45 // A Mode value is a set of flags (or 0). 46 // They control the amount of source code parsed and other optional 47 // parser functionality. 48 // 49 type Mode uint 50 51 const ( 52 PackageClauseOnly Mode = 1 << iota // stop parsing after package clause 53 ImportsOnly // stop parsing after import declarations 54 ParseComments // parse comments and add them to AST 55 Trace // print a trace of parsed productions 56 DeclarationErrors // report declaration errors 57 SpuriousErrors // same as AllErrors, for backward-compatibility 58 SkipObjectResolution // don't resolve identifiers to objects - see ParseFile 59 AllErrors = SpuriousErrors // report all errors (not just the first 10 on different lines) 60 ) 61 62 // ParseFile parses the source code of a single Go source file and returns 63 // the corresponding ast.File node. The source code may be provided via 64 // the filename of the source file, or via the src parameter. 65 // 66 // If src != nil, ParseFile parses the source from src and the filename is 67 // only used when recording position information. The type of the argument 68 // for the src parameter must be string, []byte, or io.Reader. 69 // If src == nil, ParseFile parses the file specified by filename. 70 // 71 // The mode parameter controls the amount of source text parsed and other 72 // optional parser functionality. If the SkipObjectResolution mode bit is set, 73 // the object resolution phase of parsing will be skipped, causing File.Scope, 74 // File.Unresolved, and all Ident.Obj fields to be nil. 75 // 76 // Position information is recorded in the file set fset, which must not be 77 // nil. 78 // 79 // If the source couldn't be read, the returned AST is nil and the error 80 // indicates the specific failure. If the source was read but syntax 81 // errors were found, the result is a partial AST (with ast.Bad* nodes 82 // representing the fragments of erroneous source code). Multiple errors 83 // are returned via a scanner.ErrorList which is sorted by source position. 84 // 85 func ParseFile(fset *token.FileSet, filename string, src any, mode Mode) (f *ast.File, err error) { 86 if fset == nil { 87 panic("parser.ParseFile: no token.FileSet provided (fset == nil)") 88 } 89 90 // get source 91 text, err := readSource(filename, src) 92 if err != nil { 93 return nil, err 94 } 95 96 var p parser 97 defer func() { 98 if e := recover(); e != nil { 99 // resume same panic if it's not a bailout 100 if _, ok := e.(bailout); !ok { 101 panic(e) 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 // 140 func ParseDir(fset *token.FileSet, path string, filter func(fs.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) { 141 list, err := os.ReadDir(path) 142 if err != nil { 143 return nil, err 144 } 145 146 pkgs = make(map[string]*ast.Package) 147 for _, d := range list { 148 if d.IsDir() || !strings.HasSuffix(d.Name(), ".go") { 149 continue 150 } 151 if filter != nil { 152 info, err := d.Info() 153 if err != nil { 154 return nil, err 155 } 156 if !filter(info) { 157 continue 158 } 159 } 160 filename := filepath.Join(path, d.Name()) 161 if src, err := ParseFile(fset, filename, nil, mode); err == nil { 162 name := src.Name.Name 163 pkg, found := pkgs[name] 164 if !found { 165 pkg = &ast.Package{ 166 Name: name, 167 Files: make(map[string]*ast.File), 168 } 169 pkgs[name] = pkg 170 } 171 pkg.Files[filename] = src 172 } else if first == nil { 173 first = err 174 } 175 } 176 177 return 178 } 179 180 // ParseExprFrom is a convenience function for parsing an expression. 181 // The arguments have the same meaning as for ParseFile, but the source must 182 // be a valid Go (type or value) expression. Specifically, fset must not 183 // be nil. 184 // 185 // If the source couldn't be read, the returned AST is nil and the error 186 // indicates the specific failure. If the source was read but syntax 187 // errors were found, the result is a partial AST (with ast.Bad* nodes 188 // representing the fragments of erroneous source code). Multiple errors 189 // are returned via a scanner.ErrorList which is sorted by source position. 190 // 191 func ParseExprFrom(fset *token.FileSet, filename string, src any, mode Mode) (expr ast.Expr, err error) { 192 if fset == nil { 193 panic("parser.ParseExprFrom: no token.FileSet provided (fset == nil)") 194 } 195 196 // get source 197 text, err := readSource(filename, src) 198 if err != nil { 199 return nil, err 200 } 201 202 var p parser 203 defer func() { 204 if e := recover(); e != nil { 205 // resume same panic if it's not a bailout 206 if _, ok := e.(bailout); !ok { 207 panic(e) 208 } 209 } 210 p.errors.Sort() 211 err = p.errors.Err() 212 }() 213 214 // parse expr 215 p.init(fset, filename, text, mode) 216 expr = p.parseRhsOrType() 217 218 // If a semicolon was inserted, consume it; 219 // report an error if there's more tokens. 220 if p.tok == token.SEMICOLON && p.lit == "\n" { 221 p.next() 222 } 223 p.expect(token.EOF) 224 225 return 226 } 227 228 // ParseExpr is a convenience function for obtaining the AST of an expression x. 229 // The position information recorded in the AST is undefined. The filename used 230 // in error messages is the empty string. 231 // 232 // If syntax errors were found, the result is a partial AST (with ast.Bad* nodes 233 // representing the fragments of erroneous source code). Multiple errors are 234 // returned via a scanner.ErrorList which is sorted by source position. 235 // 236 func ParseExpr(x string) (ast.Expr, error) { 237 return ParseExprFrom(token.NewFileSet(), "", []byte(x), 0) 238 } 239