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Source file src/go/ast/filter.go

Documentation: go/ast

     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  package ast
     6  
     7  import (
     8  	"go/token"
     9  	"sort"
    10  )
    11  
    12  // ----------------------------------------------------------------------------
    13  // Export filtering
    14  
    15  // exportFilter is a special filter function to extract exported nodes.
    16  func exportFilter(name string) bool {
    17  	return IsExported(name)
    18  }
    19  
    20  // FileExports trims the AST for a Go source file in place such that
    21  // only exported nodes remain: all top-level identifiers which are not exported
    22  // and their associated information (such as type, initial value, or function
    23  // body) are removed. Non-exported fields and methods of exported types are
    24  // stripped. The File.Comments list is not changed.
    25  //
    26  // FileExports reports whether there are exported declarations.
    27  //
    28  func FileExports(src *File) bool {
    29  	return filterFile(src, exportFilter, true)
    30  }
    31  
    32  // PackageExports trims the AST for a Go package in place such that
    33  // only exported nodes remain. The pkg.Files list is not changed, so that
    34  // file names and top-level package comments don't get lost.
    35  //
    36  // PackageExports reports whether there are exported declarations;
    37  // it returns false otherwise.
    38  //
    39  func PackageExports(pkg *Package) bool {
    40  	return filterPackage(pkg, exportFilter, true)
    41  }
    42  
    43  // ----------------------------------------------------------------------------
    44  // General filtering
    45  
    46  type Filter func(string) bool
    47  
    48  func filterIdentList(list []*Ident, f Filter) []*Ident {
    49  	j := 0
    50  	for _, x := range list {
    51  		if f(x.Name) {
    52  			list[j] = x
    53  			j++
    54  		}
    55  	}
    56  	return list[0:j]
    57  }
    58  
    59  // fieldName assumes that x is the type of an anonymous field and
    60  // returns the corresponding field name. If x is not an acceptable
    61  // anonymous field, the result is nil.
    62  //
    63  func fieldName(x Expr) *Ident {
    64  	switch t := x.(type) {
    65  	case *Ident:
    66  		return t
    67  	case *SelectorExpr:
    68  		if _, ok := t.X.(*Ident); ok {
    69  			return t.Sel
    70  		}
    71  	case *StarExpr:
    72  		return fieldName(t.X)
    73  	}
    74  	return nil
    75  }
    76  
    77  func filterFieldList(fields *FieldList, filter Filter, export bool) (removedFields bool) {
    78  	if fields == nil {
    79  		return false
    80  	}
    81  	list := fields.List
    82  	j := 0
    83  	for _, f := range list {
    84  		keepField := false
    85  		if len(f.Names) == 0 {
    86  			// anonymous field
    87  			name := fieldName(f.Type)
    88  			keepField = name != nil && filter(name.Name)
    89  		} else {
    90  			n := len(f.Names)
    91  			f.Names = filterIdentList(f.Names, filter)
    92  			if len(f.Names) < n {
    93  				removedFields = true
    94  			}
    95  			keepField = len(f.Names) > 0
    96  		}
    97  		if keepField {
    98  			if export {
    99  				filterType(f.Type, filter, export)
   100  			}
   101  			list[j] = f
   102  			j++
   103  		}
   104  	}
   105  	if j < len(list) {
   106  		removedFields = true
   107  	}
   108  	fields.List = list[0:j]
   109  	return
   110  }
   111  
   112  func filterCompositeLit(lit *CompositeLit, filter Filter, export bool) {
   113  	n := len(lit.Elts)
   114  	lit.Elts = filterExprList(lit.Elts, filter, export)
   115  	if len(lit.Elts) < n {
   116  		lit.Incomplete = true
   117  	}
   118  }
   119  
   120  func filterExprList(list []Expr, filter Filter, export bool) []Expr {
   121  	j := 0
   122  	for _, exp := range list {
   123  		switch x := exp.(type) {
   124  		case *CompositeLit:
   125  			filterCompositeLit(x, filter, export)
   126  		case *KeyValueExpr:
   127  			if x, ok := x.Key.(*Ident); ok && !filter(x.Name) {
   128  				continue
   129  			}
   130  			if x, ok := x.Value.(*CompositeLit); ok {
   131  				filterCompositeLit(x, filter, export)
   132  			}
   133  		}
   134  		list[j] = exp
   135  		j++
   136  	}
   137  	return list[0:j]
   138  }
   139  
   140  func filterParamList(fields *FieldList, filter Filter, export bool) bool {
   141  	if fields == nil {
   142  		return false
   143  	}
   144  	var b bool
   145  	for _, f := range fields.List {
   146  		if filterType(f.Type, filter, export) {
   147  			b = true
   148  		}
   149  	}
   150  	return b
   151  }
   152  
   153  func filterType(typ Expr, f Filter, export bool) bool {
   154  	switch t := typ.(type) {
   155  	case *Ident:
   156  		return f(t.Name)
   157  	case *ParenExpr:
   158  		return filterType(t.X, f, export)
   159  	case *ArrayType:
   160  		return filterType(t.Elt, f, export)
   161  	case *StructType:
   162  		if filterFieldList(t.Fields, f, export) {
   163  			t.Incomplete = true
   164  		}
   165  		return len(t.Fields.List) > 0
   166  	case *FuncType:
   167  		b1 := filterParamList(t.Params, f, export)
   168  		b2 := filterParamList(t.Results, f, export)
   169  		return b1 || b2
   170  	case *InterfaceType:
   171  		if filterFieldList(t.Methods, f, export) {
   172  			t.Incomplete = true
   173  		}
   174  		return len(t.Methods.List) > 0
   175  	case *MapType:
   176  		b1 := filterType(t.Key, f, export)
   177  		b2 := filterType(t.Value, f, export)
   178  		return b1 || b2
   179  	case *ChanType:
   180  		return filterType(t.Value, f, export)
   181  	}
   182  	return false
   183  }
   184  
   185  func filterSpec(spec Spec, f Filter, export bool) bool {
   186  	switch s := spec.(type) {
   187  	case *ValueSpec:
   188  		s.Names = filterIdentList(s.Names, f)
   189  		s.Values = filterExprList(s.Values, f, export)
   190  		if len(s.Names) > 0 {
   191  			if export {
   192  				filterType(s.Type, f, export)
   193  			}
   194  			return true
   195  		}
   196  	case *TypeSpec:
   197  		if f(s.Name.Name) {
   198  			if export {
   199  				filterType(s.Type, f, export)
   200  			}
   201  			return true
   202  		}
   203  		if !export {
   204  			// For general filtering (not just exports),
   205  			// filter type even if name is not filtered
   206  			// out.
   207  			// If the type contains filtered elements,
   208  			// keep the declaration.
   209  			return filterType(s.Type, f, export)
   210  		}
   211  	}
   212  	return false
   213  }
   214  
   215  func filterSpecList(list []Spec, f Filter, export bool) []Spec {
   216  	j := 0
   217  	for _, s := range list {
   218  		if filterSpec(s, f, export) {
   219  			list[j] = s
   220  			j++
   221  		}
   222  	}
   223  	return list[0:j]
   224  }
   225  
   226  // FilterDecl trims the AST for a Go declaration in place by removing
   227  // all names (including struct field and interface method names, but
   228  // not from parameter lists) that don't pass through the filter f.
   229  //
   230  // FilterDecl reports whether there are any declared names left after
   231  // filtering.
   232  //
   233  func FilterDecl(decl Decl, f Filter) bool {
   234  	return filterDecl(decl, f, false)
   235  }
   236  
   237  func filterDecl(decl Decl, f Filter, export bool) bool {
   238  	switch d := decl.(type) {
   239  	case *GenDecl:
   240  		d.Specs = filterSpecList(d.Specs, f, export)
   241  		return len(d.Specs) > 0
   242  	case *FuncDecl:
   243  		return f(d.Name.Name)
   244  	}
   245  	return false
   246  }
   247  
   248  // FilterFile trims the AST for a Go file in place by removing all
   249  // names from top-level declarations (including struct field and
   250  // interface method names, but not from parameter lists) that don't
   251  // pass through the filter f. If the declaration is empty afterwards,
   252  // the declaration is removed from the AST. Import declarations are
   253  // always removed. The File.Comments list is not changed.
   254  //
   255  // FilterFile reports whether there are any top-level declarations
   256  // left after filtering.
   257  //
   258  func FilterFile(src *File, f Filter) bool {
   259  	return filterFile(src, f, false)
   260  }
   261  
   262  func filterFile(src *File, f Filter, export bool) bool {
   263  	j := 0
   264  	for _, d := range src.Decls {
   265  		if filterDecl(d, f, export) {
   266  			src.Decls[j] = d
   267  			j++
   268  		}
   269  	}
   270  	src.Decls = src.Decls[0:j]
   271  	return j > 0
   272  }
   273  
   274  // FilterPackage trims the AST for a Go package in place by removing
   275  // all names from top-level declarations (including struct field and
   276  // interface method names, but not from parameter lists) that don't
   277  // pass through the filter f. If the declaration is empty afterwards,
   278  // the declaration is removed from the AST. The pkg.Files list is not
   279  // changed, so that file names and top-level package comments don't get
   280  // lost.
   281  //
   282  // FilterPackage reports whether there are any top-level declarations
   283  // left after filtering.
   284  //
   285  func FilterPackage(pkg *Package, f Filter) bool {
   286  	return filterPackage(pkg, f, false)
   287  }
   288  
   289  func filterPackage(pkg *Package, f Filter, export bool) bool {
   290  	hasDecls := false
   291  	for _, src := range pkg.Files {
   292  		if filterFile(src, f, export) {
   293  			hasDecls = true
   294  		}
   295  	}
   296  	return hasDecls
   297  }
   298  
   299  // ----------------------------------------------------------------------------
   300  // Merging of package files
   301  
   302  // The MergeMode flags control the behavior of MergePackageFiles.
   303  type MergeMode uint
   304  
   305  const (
   306  	// If set, duplicate function declarations are excluded.
   307  	FilterFuncDuplicates MergeMode = 1 << iota
   308  	// If set, comments that are not associated with a specific
   309  	// AST node (as Doc or Comment) are excluded.
   310  	FilterUnassociatedComments
   311  	// If set, duplicate import declarations are excluded.
   312  	FilterImportDuplicates
   313  )
   314  
   315  // nameOf returns the function (foo) or method name (foo.bar) for
   316  // the given function declaration. If the AST is incorrect for the
   317  // receiver, it assumes a function instead.
   318  //
   319  func nameOf(f *FuncDecl) string {
   320  	if r := f.Recv; r != nil && len(r.List) == 1 {
   321  		// looks like a correct receiver declaration
   322  		t := r.List[0].Type
   323  		// dereference pointer receiver types
   324  		if p, _ := t.(*StarExpr); p != nil {
   325  			t = p.X
   326  		}
   327  		// the receiver type must be a type name
   328  		if p, _ := t.(*Ident); p != nil {
   329  			return p.Name + "." + f.Name.Name
   330  		}
   331  		// otherwise assume a function instead
   332  	}
   333  	return f.Name.Name
   334  }
   335  
   336  // separator is an empty //-style comment that is interspersed between
   337  // different comment groups when they are concatenated into a single group
   338  //
   339  var separator = &Comment{token.NoPos, "//"}
   340  
   341  // MergePackageFiles creates a file AST by merging the ASTs of the
   342  // files belonging to a package. The mode flags control merging behavior.
   343  //
   344  func MergePackageFiles(pkg *Package, mode MergeMode) *File {
   345  	// Count the number of package docs, comments and declarations across
   346  	// all package files. Also, compute sorted list of filenames, so that
   347  	// subsequent iterations can always iterate in the same order.
   348  	ndocs := 0
   349  	ncomments := 0
   350  	ndecls := 0
   351  	filenames := make([]string, len(pkg.Files))
   352  	i := 0
   353  	for filename, f := range pkg.Files {
   354  		filenames[i] = filename
   355  		i++
   356  		if f.Doc != nil {
   357  			ndocs += len(f.Doc.List) + 1 // +1 for separator
   358  		}
   359  		ncomments += len(f.Comments)
   360  		ndecls += len(f.Decls)
   361  	}
   362  	sort.Strings(filenames)
   363  
   364  	// Collect package comments from all package files into a single
   365  	// CommentGroup - the collected package documentation. In general
   366  	// there should be only one file with a package comment; but it's
   367  	// better to collect extra comments than drop them on the floor.
   368  	var doc *CommentGroup
   369  	var pos token.Pos
   370  	if ndocs > 0 {
   371  		list := make([]*Comment, ndocs-1) // -1: no separator before first group
   372  		i := 0
   373  		for _, filename := range filenames {
   374  			f := pkg.Files[filename]
   375  			if f.Doc != nil {
   376  				if i > 0 {
   377  					// not the first group - add separator
   378  					list[i] = separator
   379  					i++
   380  				}
   381  				for _, c := range f.Doc.List {
   382  					list[i] = c
   383  					i++
   384  				}
   385  				if f.Package > pos {
   386  					// Keep the maximum package clause position as
   387  					// position for the package clause of the merged
   388  					// files.
   389  					pos = f.Package
   390  				}
   391  			}
   392  		}
   393  		doc = &CommentGroup{list}
   394  	}
   395  
   396  	// Collect declarations from all package files.
   397  	var decls []Decl
   398  	if ndecls > 0 {
   399  		decls = make([]Decl, ndecls)
   400  		funcs := make(map[string]int) // map of func name -> decls index
   401  		i := 0                        // current index
   402  		n := 0                        // number of filtered entries
   403  		for _, filename := range filenames {
   404  			f := pkg.Files[filename]
   405  			for _, d := range f.Decls {
   406  				if mode&FilterFuncDuplicates != 0 {
   407  					// A language entity may be declared multiple
   408  					// times in different package files; only at
   409  					// build time declarations must be unique.
   410  					// For now, exclude multiple declarations of
   411  					// functions - keep the one with documentation.
   412  					//
   413  					// TODO(gri): Expand this filtering to other
   414  					//            entities (const, type, vars) if
   415  					//            multiple declarations are common.
   416  					if f, isFun := d.(*FuncDecl); isFun {
   417  						name := nameOf(f)
   418  						if j, exists := funcs[name]; exists {
   419  							// function declared already
   420  							if decls[j] != nil && decls[j].(*FuncDecl).Doc == nil {
   421  								// existing declaration has no documentation;
   422  								// ignore the existing declaration
   423  								decls[j] = nil
   424  							} else {
   425  								// ignore the new declaration
   426  								d = nil
   427  							}
   428  							n++ // filtered an entry
   429  						} else {
   430  							funcs[name] = i
   431  						}
   432  					}
   433  				}
   434  				decls[i] = d
   435  				i++
   436  			}
   437  		}
   438  
   439  		// Eliminate nil entries from the decls list if entries were
   440  		// filtered. We do this using a 2nd pass in order to not disturb
   441  		// the original declaration order in the source (otherwise, this
   442  		// would also invalidate the monotonically increasing position
   443  		// info within a single file).
   444  		if n > 0 {
   445  			i = 0
   446  			for _, d := range decls {
   447  				if d != nil {
   448  					decls[i] = d
   449  					i++
   450  				}
   451  			}
   452  			decls = decls[0:i]
   453  		}
   454  	}
   455  
   456  	// Collect import specs from all package files.
   457  	var imports []*ImportSpec
   458  	if mode&FilterImportDuplicates != 0 {
   459  		seen := make(map[string]bool)
   460  		for _, filename := range filenames {
   461  			f := pkg.Files[filename]
   462  			for _, imp := range f.Imports {
   463  				if path := imp.Path.Value; !seen[path] {
   464  					// TODO: consider handling cases where:
   465  					// - 2 imports exist with the same import path but
   466  					//   have different local names (one should probably
   467  					//   keep both of them)
   468  					// - 2 imports exist but only one has a comment
   469  					// - 2 imports exist and they both have (possibly
   470  					//   different) comments
   471  					imports = append(imports, imp)
   472  					seen[path] = true
   473  				}
   474  			}
   475  		}
   476  	} else {
   477  		for _, f := range pkg.Files {
   478  			imports = append(imports, f.Imports...)
   479  		}
   480  	}
   481  
   482  	// Collect comments from all package files.
   483  	var comments []*CommentGroup
   484  	if mode&FilterUnassociatedComments == 0 {
   485  		comments = make([]*CommentGroup, ncomments)
   486  		i := 0
   487  		for _, f := range pkg.Files {
   488  			i += copy(comments[i:], f.Comments)
   489  		}
   490  	}
   491  
   492  	// TODO(gri) need to compute unresolved identifiers!
   493  	return &File{doc, pos, NewIdent(pkg.Name), decls, pkg.Scope, imports, nil, comments}
   494  }
   495  

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