javascript - rename.go

     1  package minify
     2  
     3  import (
     4  	"sort"
     5  
     6  	"vimagination.zapto.org/javascript"
     7  	"vimagination.zapto.org/javascript/scope"
     8  )
     9  
    10  type binding struct {
    11  	Name, OriginalName string
    12  	Scope              *scope.Scope
    13  	NameSet            bool
    14  }
    15  
    16  func orderedScope(s *scope.Scope) []binding {
    17  	b := walkScope(s, nil)
    18  	sort.Slice(b, func(i, j int) bool {
    19  		if b[i].NameSet {
    20  			if !b[j].NameSet {
    21  				return false
    22  			}
    23  		} else if b[j].NameSet {
    24  			return true
    25  		}
    26  		il := len(b[i].Scope.Bindings[b[i].Name])
    27  		jl := len(b[j].Scope.Bindings[b[j].Name])
    28  
    29  		if il == jl {
    30  			return b[i].Name < b[j].Name
    31  		}
    32  		return il > jl
    33  	})
    34  	return b
    35  }
    36  
    37  func walkScope(s *scope.Scope, b []binding) []binding {
    38  	for name := range s.Bindings {
    39  		if name == "this" || name == "arguments" {
    40  			continue
    41  		}
    42  		b = append(b, binding{
    43  			Name:         name,
    44  			OriginalName: name,
    45  			Scope:        s,
    46  			NameSet:      s.Bindings[name][0].BindingType == scope.BindingRef,
    47  		})
    48  	}
    49  	for _, cs := range s.Scopes {
    50  		b = walkScope(cs, b)
    51  	}
    52  	return b
    53  }
    54  
    55  func renameIdentifiers(m *javascript.Module) error {
    56  	s, err := scope.ModuleScope(m, nil)
    57  	if err != nil {
    58  		return err
    59  	}
    60  	bindings := orderedScope(s)
    61  	for n, binding := range bindings {
    62  		if binding.NameSet {
    63  			break
    64  		}
    65  		identifiersInScope := make(map[string]struct{})
    66  		for _, checkBinding := range bindings {
    67  			if !checkBinding.NameSet || checkBinding == binding {
    68  				continue
    69  			}
    70  			if binding.Scope == checkBinding.Scope {
    71  				identifiersInScope[checkBinding.Name] = struct{}{}
    72  			} else if isParentScope(binding.Scope, checkBinding.Scope) {
    73  				for _, scope := range binding.Scope.Bindings[binding.OriginalName] {
    74  					if isParentScope(checkBinding.Scope, scope.Scope) {
    75  						identifiersInScope[checkBinding.Name] = struct{}{}
    76  						break
    77  					}
    78  				}
    79  			} else if isParentScope(checkBinding.Scope, binding.Scope) {
    80  				for _, scope := range checkBinding.Scope.Bindings[checkBinding.OriginalName] {
    81  					if isParentScope(binding.Scope, scope.Scope) {
    82  						identifiersInScope[checkBinding.Name] = struct{}{}
    83  						break
    84  					}
    85  				}
    86  			}
    87  		}
    88  		name := makeUniqueName(identifiersInScope)
    89  		for _, b := range binding.Scope.Bindings[binding.Name] {
    90  			b.Data = name
    91  		}
    92  		bindings[n].Name = name
    93  		bindings[n].NameSet = true
    94  	}
    95  	return nil
    96  }
    97  
    98  func isParentScope(a, b *scope.Scope) bool {
    99  	for b != nil {
   100  		if b == a {
   101  			return true
   102  		}
   103  		b = b.Parent
   104  	}
   105  	return false
   106  }
   107  
   108  var (
   109  	extraChars = []byte("0123456789_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$")
   110  	startChars = extraChars[10:]
   111  )
   112  
   113  func makeUniqueName(exclude map[string]struct{}) string {
   114  	name := make([]byte, 8)
   115  	parts := make([][]byte, 8)
   116  	for l := 0; ; l++ {
   117  		parts = parts[:1]
   118  		parts[0] = startChars
   119  		for n := 0; n < l; n++ {
   120  			parts = append(parts, extraChars)
   121  		}
   122  	L:
   123  		for {
   124  			name = name[:0]
   125  			for i := 0; i <= l; i++ {
   126  				name = append(name, parts[i][0])
   127  			}
   128  			if _, ok := exclude[string(name)]; !ok {
   129  				return string(name)
   130  			}
   131  			for i := l; i >= 0; i-- {
   132  				parts[i] = parts[i][1:]
   133  				if len(parts[i]) > 0 {
   134  					break
   135  				}
   136  				if i == 0 {
   137  					break L
   138  				}
   139  				parts[i] = extraChars
   140  			}
   141  		}
   142  	}
   143  }
   144