libgo/go/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         "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 interface{}) ([]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                         var buf bytes.Buffer
  39                         if _, err := io.Copy(&buf, s); err != nil {
  40                                 return nil, err
  41                         }
  42                         return buf.Bytes(), nil
  43                 }
  44                 return nil, errors.New("invalid source")
  45         }
  46         return ioutil.ReadFile(filename)
  47 }
  48
  49 // A Mode value is a set of flags (or 0).
  50 // They control the amount of source code parsed and other optional
  51 // parser functionality.
  52 //
  53 type Mode uint
  54
  55 const (
  56         PackageClauseOnly Mode             = 1 << iota // stop parsing after package clause
  57         ImportsOnly                                    // stop parsing after import declarations
  58         ParseComments                                  // parse comments and add them to AST
  59         Trace                                          // print a trace of parsed productions
  60         DeclarationErrors                              // report declaration errors
  61         SpuriousErrors                                 // same as AllErrors, for backward-compatibility
  62         AllErrors         = SpuriousErrors             // report all errors (not just the first 10 on different lines)
  63 )
  64
  65 // ParseFile parses the source code of a single Go source file and returns
  66 // the corresponding ast.File node. The source code may be provided via
  67 // the filename of the source file, or via the src parameter.
  68 //
  69 // If src != nil, ParseFile parses the source from src and the filename is
  70 // only used when recording position information. The type of the argument
  71 // for the src parameter must be string, []byte, or io.Reader.
  72 // If src == nil, ParseFile parses the file specified by filename.
  73 //
  74 // The mode parameter controls the amount of source text parsed and other
  75 // optional parser functionality. Position information is recorded in the
  76 // file set fset.
  77 //
  78 // If the source couldn't be read, the returned AST is nil and the error
  79 // indicates the specific failure. If the source was read but syntax
  80 // errors were found, the result is a partial AST (with ast.Bad* nodes
  81 // representing the fragments of erroneous source code). Multiple errors
  82 // are returned via a scanner.ErrorList which is sorted by file position.
  83 //
  84 func ParseFile(fset *token.FileSet, filename string, src interface{}, mode Mode) (f *ast.File, err error) {
  85         // get source
  86         text, err := readSource(filename, src)
  87         if err != nil {
  88                 return nil, err
  89         }
  90
  91         var p parser
  92         defer func() {
  93                 if e := recover(); e != nil {
  94                         _ = e.(bailout) // re-panics if it's not a bailout
  95                 }
  96
  97                 // set result values
  98                 if f == nil {
  99                         // source is not a valid Go source file - satisfy
 100                         // ParseFile API and return a valid (but) empty
 101                         // *ast.File
 102                         f = &ast.File{
 103                                 Name:  new(ast.Ident),
 104                                 Scope: ast.NewScope(nil),
 105                         }
 106                 }
 107
 108                 p.errors.Sort()
 109                 err = p.errors.Err()
 110         }()
 111
 112         // parse source
 113         p.init(fset, filename, text, mode)
 114         f = p.parseFile()
 115
 116         return
 117 }
 118
 119 // ParseDir calls ParseFile for all files with names ending in ".go" in the
 120 // directory specified by path and returns a map of package name -> package
 121 // AST with all the packages found.
 122 //
 123 // If filter != nil, only the files with os.FileInfo entries passing through
 124 // the filter (and ending in ".go") are considered. The mode bits are passed
 125 // to ParseFile unchanged. Position information is recorded in fset.
 126 //
 127 // If the directory couldn't be read, a nil map and the respective error are
 128 // returned. If a parse error occurred, a non-nil but incomplete map and the
 129 // first error encountered are returned.
 130 //
 131 func ParseDir(fset *token.FileSet, path string, filter func(os.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) {
 132         fd, err := os.Open(path)
 133         if err != nil {
 134                 return nil, err
 135         }
 136         defer fd.Close()
 137
 138         list, err := fd.Readdir(-1)
 139         if err != nil {
 140                 return nil, err
 141         }
 142
 143         pkgs = make(map[string]*ast.Package)
 144         for _, d := range list {
 145                 if strings.HasSuffix(d.Name(), ".go") && (filter == nil || filter(d)) {
 146                         filename := filepath.Join(path, d.Name())
 147                         if src, err := ParseFile(fset, filename, nil, mode); err == nil {
 148                                 name := src.Name.Name
 149                                 pkg, found := pkgs[name]
 150                                 if !found {
 151                                         pkg = &ast.Package{
 152                                                 Name:  name,
 153                                                 Files: make(map[string]*ast.File),
 154                                         }
 155                                         pkgs[name] = pkg
 156                                 }
 157                                 pkg.Files[filename] = src
 158                         } else if first == nil {
 159                                 first = err
 160                         }
 161                 }
 162         }
 163
 164         return
 165 }
 166
 167 // ParseExpr is a convenience function for obtaining the AST of an expression x.
 168 // The position information recorded in the AST is undefined. The filename used
 169 // in error messages is the empty string.
 170 //
 171 func ParseExpr(x string) (ast.Expr, error) {
 172         var p parser
 173         p.init(token.NewFileSet(), "", []byte(x), 0)
 174
 175         // Set up pkg-level scopes to avoid nil-pointer errors.
 176         // This is not needed for a correct expression x as the
 177         // parser will be ok with a nil topScope, but be cautious
 178         // in case of an erroneous x.
 179         p.openScope()
 180         p.pkgScope = p.topScope
 181         e := p.parseRhsOrType()
 182         p.closeScope()
 183         assert(p.topScope == nil, "unbalanced scopes")
 184
 185         // If a semicolon was inserted, consume it;
 186         // report an error if there's more tokens.
 187         if p.tok == token.SEMICOLON {
 188                 p.next()
 189         }
 190         p.expect(token.EOF)
 191
 192         if p.errors.Len() > 0 {
 193                 p.errors.Sort()
 194                 return nil, p.errors.Err()
 195         }
 196
 197         return e, nil
 198 }