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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/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 && p.lit == "\n" {
   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	}
   199	

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