-
Notifications
You must be signed in to change notification settings - Fork 1.1k
/
RemoveUnusedVars.java
1809 lines (1613 loc) · 65.2 KB
/
RemoveUnusedVars.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* Copyright 2008 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;
import com.google.javascript.jscomp.CodingConvention.SubclassRelationship;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import javax.annotation.Nullable;
/**
* Garbage collection for variable and function definitions. Basically performs
* a mark-and-sweep type algorithm over the JavaScript parse tree.
*
* For each scope:
* (1) Scan the variable/function declarations at that scope.
* (2) Traverse the scope for references, marking all referenced variables.
* Unlike other compiler passes, this is a pre-order traversal, not a
* post-order traversal.
* (3) If the traversal encounters an assign without other side-effects,
* create a continuation. Continue the continuation iff the assigned
* variable is referenced.
* (4) When the traversal completes, remove all unreferenced variables.
*
* If it makes it easier, you can think of the continuations of the traversal
* as a reference graph. Each continuation represents a set of edges, where the
* source node is a known variable, and the destination nodes are lazily
* evaluated when the continuation is executed.
*
* This algorithm is similar to the algorithm used by {@code SmartNameRemoval}.
* {@code SmartNameRemoval} maintains an explicit graph of dependencies
* between global symbols. However, {@code SmartNameRemoval} cannot handle
* non-trivial edges in the reference graph ("A is referenced iff both B and C
* are referenced"), or local variables. {@code SmartNameRemoval} is also
* substantially more complicated because it tries to handle namespaces
* (which is largely unnecessary in the presence of {@code CollapseProperties}.
*
* This pass also uses a more complex analysis of assignments, where
* an assignment to a variable or a property of that variable does not
* necessarily count as a reference to that variable, unless we can prove
* that it modifies external state. This is similar to
* {@code FlowSensitiveInlineVariables}, except that it works for variables
* used across scopes.
*
* Multiple datastructures are used to accumulate nodes, some of which are
* later removed. Since some nodes encompass a subtree of nodes, the removal
* can sometimes pre-remove other nodes which are also referenced in these
* datastructures for later removal. Attempting double-removal violates scope
* change notification constraints so there is a desire to excise
* already-removed subtree nodes from these datastructures. But not all of the
* datastructures are conducive to flexible removal and the ones that are
* conducive don't necessarily track all flavors of nodes. So instead of
* updating datastructures on the fly a pre-check is performed to skip
* already-removed nodes right before the moment an attempt to remove them
* would otherwise be made.
*
* @author nicksantos@google.com (Nick Santos)
*/
class RemoveUnusedVars implements CompilerPass {
// Properties that are implicitly used as part of the JS language.
private static final ImmutableSet<String> IMPLICITLY_USED_PROPERTIES =
ImmutableSet.of("length", "toString", "valueOf", "constructor");
private final AbstractCompiler compiler;
private final CodingConvention codingConvention;
private final boolean removeGlobals;
private final boolean preserveFunctionExpressionNames;
/**
* Used to hold continuations that need to be invoked.
*
* When we find a subtree of the AST that may not need to be traversed, we create a Continuation
* for it. If we later discover that we do need to traverse it, we add it to this worklist
* rather than traversing it immediately. If we invoked the traversal immediately, we could
* end up modifying a data structure in the traversal as we're iterating over it.
*/
private final Deque<Continuation> worklist = new ArrayDeque<>();
private final Map<Var, VarInfo> varInfoMap = new HashMap<>();
private final Set<String> referencedPropertyNames = new HashSet<>(IMPLICITLY_USED_PROPERTIES);
/** Stores Removable objects for each property name that is currently considered removable. */
private final Multimap<String, Removable> removablesForPropertyNames = HashMultimap.create();
/** Single value to use for all vars for which we cannot remove anything at all. */
private final VarInfo canonicalTotallyUnremovableVarInfo;
/**
* Keep track of scopes that we've traversed.
*/
private final List<Scope> allFunctionParamScopes = new ArrayList<>();
private final ScopeCreator scopeCreator;
private final boolean removeUnusedProperties;
RemoveUnusedVars(
AbstractCompiler compiler,
boolean removeGlobals,
boolean preserveFunctionExpressionNames,
boolean removeUnusedProperties) {
this.compiler = compiler;
this.codingConvention = compiler.getCodingConvention();
this.removeGlobals = removeGlobals;
this.preserveFunctionExpressionNames = preserveFunctionExpressionNames;
this.removeUnusedProperties = removeUnusedProperties;
this.scopeCreator = new Es6SyntacticScopeCreator(compiler);
// All Vars that are completely unremovable will share this VarInfo instance.
canonicalTotallyUnremovableVarInfo = new VarInfo();
canonicalTotallyUnremovableVarInfo.setIsExplicitlyNotRemovable();
}
/**
* Traverses the root, removing all unused variables. Multiple traversals
* may occur to ensure all unused variables are removed.
*/
@Override
public void process(Node externs, Node root) {
checkState(compiler.getLifeCycleStage().isNormalized());
if (removeUnusedProperties) {
referencedPropertyNames.addAll(compiler.getExternProperties());
}
traverseAndRemoveUnusedReferences(root);
}
/**
* Traverses a node recursively. Call this once per pass.
*/
private void traverseAndRemoveUnusedReferences(Node root) {
// TODO(bradfordcsmith): Include externs in the scope.
// Since we don't do this now, scope.getVar(someExtern) returns null.
Scope scope = scopeCreator.createScope(root, null);
worklist.add(new Continuation(root, scope));
while (!worklist.isEmpty()) {
Continuation continuation = worklist.remove();
continuation.apply();
}
removeUnreferencedVars();
if (removeUnusedProperties) {
removeUnreferencedProperties();
}
for (Scope fparamScope : allFunctionParamScopes) {
removeUnreferencedFunctionArgs(fparamScope);
}
}
private void removeUnreferencedProperties() {
for (Removable removable : removablesForPropertyNames.values()) {
removable.remove(compiler);
}
}
/**
* Traverses everything in the current scope and marks variables that
* are referenced.
*
* During traversal, we identify subtrees that will only be
* referenced if their enclosing variables are referenced. Instead of
* traversing those subtrees, we create a continuation for them,
* and traverse them lazily.
*/
private void traverseNode(Node n, Scope scope) {
Node parent = n.getParent();
Token type = n.getToken();
Var var = null;
switch (type) {
case CATCH:
traverseCatch(n, scope);
break;
case FUNCTION:
{
VarInfo varInfo = null;
// If this function is a removable var, then create a continuation
// for it instead of traversing immediately.
if (NodeUtil.isFunctionDeclaration(n)) {
varInfo = traverseVar(scope.getVar(n.getFirstChild().getString()));
FunctionDeclaration functionDeclaration =
new RemovableBuilder()
.addContinuation(new Continuation(n, scope))
.buildFunctionDeclaration(n);
varInfo.addRemovable(functionDeclaration);
if (parent.isExport()) {
varInfo.markAsReferenced();
}
} else {
traverseFunction(n, scope);
}
}
break;
case ASSIGN:
traverseAssign(n, scope);
break;
case CALL:
traverseCall(n, scope);
break;
case BLOCK:
// This case if for if there are let and const variables in block scopes.
// Otherwise other variables will be hoisted up into the global scope and already be
// handled.
traverseChildren(
n, NodeUtil.createsBlockScope(n) ? scopeCreator.createScope(n, scope) : scope);
break;
case MODULE_BODY:
traverseChildren(n, scopeCreator.createScope(n, scope));
break;
case CLASS:
traverseClass(n, scope);
break;
case CLASS_MEMBERS:
traverseClassMembers(n, scope);
break;
case DEFAULT_VALUE:
traverseDefaultValue(n, scope);
break;
case REST:
traverseRest(n, scope);
break;
case ARRAY_PATTERN:
traverseArrayPattern(n, scope);
break;
case OBJECT_PATTERN:
traverseObjectPattern(n, scope);
break;
case OBJECTLIT:
traverseObjectLiteral(n, scope);
break;
case FOR:
traverseVanillaFor(n, scope);
break;
case FOR_IN:
case FOR_OF:
traverseEnhancedFor(n, scope);
break;
case LET:
case CONST:
case VAR:
// for-loop cases are handled by custom traversal methods.
checkState(NodeUtil.isStatement(n));
traverseDeclarationStatement(n, scope);
break;
case NAME:
// The only cases that should reach this point are parameter declarations and references
// to names. The name node does not have children in these cases.
checkState(!n.hasChildren());
// the parameter declaration is not a read of the name
if (!parent.isParamList()) {
// var|let|const name;
// are handled at a higher level.
checkState(!NodeUtil.isNameDeclaration(parent));
// function name() {}
// class name() {}
// handled at a higher level
checkState(!((parent.isFunction() || parent.isClass()) && parent.getFirstChild() == n));
var = scope.getVar(n.getString());
if (var != null) {
// All name references that aren't handled elsewhere are references to vars.
traverseVar(var).markAsReferenced();
}
}
break;
case GETPROP:
Node objectNode = n.getFirstChild();
Node propertyNameNode = objectNode.getNext();
String propertyName = propertyNameNode.getString();
markPropertyNameReferenced(propertyName);
traverseNode(objectNode, scope);
break;
default:
traverseChildren(n, scope);
break;
}
}
private void traverseCall(Node callNode, Scope scope) {
Node parent = callNode.getParent();
String classVarName = null;
// A call that is a statement unto itself or the left side of a comma expression might be
// a call to a known method for doing class setup
// e.g. $jscomp.inherits(Class, BaseClass) or goog.addSingletonGetter(Class)
// Such methods never have meaningful return values, so we won't look for them in other
// contexts
if (parent.isExprResult() || (parent.isComma() && parent.getFirstChild() == callNode)) {
SubclassRelationship subclassRelationship =
codingConvention.getClassesDefinedByCall(callNode);
if (subclassRelationship != null) {
// e.g. goog.inherits(DerivedClass, BaseClass);
// NOTE: DerivedClass and BaseClass must be QNames. Otherwise getClassesDefinedByCall() will
// return null.
classVarName = subclassRelationship.subclassName;
} else {
// Look for calls to addSingletonGetter calls.
classVarName = codingConvention.getSingletonGetterClassName(callNode);
}
}
Var classVar = (classVarName == null) ? null : scope.getVar(classVarName);
if (classVar == null || !classVar.isGlobal()) {
// This isn't one of the special call types, or it isn't acting on a global class name.
// It would be more correct to only not track when the class name does not
// reference a constructor, but checking that it is a global is easier and mostly the same.
traverseChildren(callNode, scope);
} else {
VarInfo classVarInfo = traverseVar(classVar);
RemovableBuilder builder = new RemovableBuilder();
for (Node child = callNode.getFirstChild(); child != null; child = child.getNext()) {
builder.addContinuation(new Continuation(child, scope));
}
classVarInfo.addRemovable(builder.buildClassSetupCall(callNode));
}
}
private void traverseRest(Node restNode, Scope scope) {
Node target = restNode.getOnlyChild();
if (!target.isName()) {
traverseNode(target, scope);
} else {
Var var = scope.getVar(target.getString());
if (var != null) {
VarInfo varInfo = traverseVar(var);
// NOTE: DestructuringAssign is currently used for both actual destructuring and
// default or rest parameters.
// TODO(bradfordcsmith): Maybe distinguish between these 2 cases.
varInfo.addRemovable(new RemovableBuilder().buildDestructuringAssign(restNode, target));
}
}
}
private void traverseObjectLiteral(Node objectLiteral, Scope scope) {
for (Node propertyNode = objectLiteral.getFirstChild();
propertyNode != null;
propertyNode = propertyNode.getNext()) {
if (propertyNode.isStringKey() && !propertyNode.isQuotedString()) {
// An unquoted property name in an object literal counts as a reference to that property
// name, because of some reflection patterns.
// TODO(bradfordcsmith): Handle this better for `Foo.prototype = {a: 1, b: 2}`
markPropertyNameReferenced(propertyNode.getString());
traverseNode(propertyNode.getFirstChild(), scope);
} else {
traverseNode(propertyNode, scope);
}
}
}
private void traverseCatch(Node catchNode, Scope scope) {
Node exceptionNameNode = catchNode.getFirstChild();
Node block = exceptionNameNode.getNext();
VarInfo exceptionVarInfo =
traverseVar(scope.getVar(exceptionNameNode.getString()));
exceptionVarInfo.setIsExplicitlyNotRemovable();
traverseNode(block, scope);
}
private void traverseEnhancedFor(Node enhancedFor, Scope scope) {
Scope forScope = scopeCreator.createScope(enhancedFor, scope);
// for (iterationTarget in|of collection) body;
Node iterationTarget = enhancedFor.getFirstChild();
Node collection = iterationTarget.getNext();
Node body = collection.getNext();
if (iterationTarget.isName()) {
// using previously-declared loop variable. e.g.
// `for (varName of collection) {}`
Var var = forScope.getVar(iterationTarget.getString());
// NOTE: var will be null if it was declared in externs
if (var != null) {
VarInfo varInfo = traverseVar(var);
varInfo.setIsExplicitlyNotRemovable();
}
} else if (NodeUtil.isNameDeclaration(iterationTarget)) {
// loop has const/var/let declaration
Node declNode = iterationTarget.getOnlyChild();
if (declNode.isDestructuringLhs()) {
// e.g.
// `for (const [a, b] of pairList) {}`
// destructuring is handled at a lower level
// Note that destructuring assignments are always considered to set an unknown value
// equivalent to what we set for the var name case above and below.
// It isn't necessary to set the variable names as not removable, though, because the
// thing that isn't removable is the destructuring pattern itself, which we never remove.
// TODO(bradfordcsmith): The need to explain all the above shows this should be reworked.
traverseNode(declNode, forScope);
} else {
// e.g.
// `for (const varName of collection) {}`
checkState(declNode.isName());
checkState(!declNode.hasChildren());
// We can never remove the loop variable of a for-in or for-of loop, because it's
// essential to loop syntax.
VarInfo varInfo = traverseVar(forScope.getVar(declNode.getString()));
varInfo.setIsExplicitlyNotRemovable();
}
} else {
// using some general LHS value e.g.
// `for ([a, b] of collection) {}` destructuring with existing vars
// `for (a.x of collection) {}` using a property as the loop var
// TODO(bradfordcsmith): This should be considered a write if it's a property reference.
traverseNode(iterationTarget, forScope);
}
traverseNode(collection, forScope);
traverseNode(body, forScope);
}
private void traverseVanillaFor(Node forNode, Scope scope) {
Scope forScope = scopeCreator.createScope(forNode, scope);
Node initialization = forNode.getFirstChild();
Node condition = initialization.getNext();
Node update = condition.getNext();
Node block = update.getNext();
if (NodeUtil.isNameDeclaration(initialization)) {
traverseVanillaForNameDeclarations(initialization, forScope);
} else {
traverseNode(initialization, forScope);
}
traverseNode(condition, forScope);
traverseNode(update, forScope);
traverseNode(block, forScope);
}
private void traverseVanillaForNameDeclarations(Node nameDeclaration, Scope scope) {
for (Node child = nameDeclaration.getFirstChild(); child != null; child = child.getNext()) {
if (!child.isName()) {
// TODO(bradfordcsmith): Customize handling of destructuring
traverseNode(child, scope);
} else {
Node nameNode = child;
@Nullable Node valueNode = child.getFirstChild();
VarInfo varInfo = traverseVar(scope.getVar(nameNode.getString()));
if (valueNode == null) {
varInfo.addRemovable(new RemovableBuilder().buildVanillaForNameDeclaration(nameNode));
} else if (NodeUtil.mayHaveSideEffects(valueNode)) {
// TODO(bradfordcsmith): Actually allow for removing the variable while keeping the
// valueNode for its side-effects.
varInfo.setIsExplicitlyNotRemovable();
traverseNode(valueNode, scope);
} else {
VanillaForNameDeclaration vanillaForNameDeclaration =
new RemovableBuilder()
.setAssignedValue(valueNode)
.addContinuation(new Continuation(valueNode, scope))
.buildVanillaForNameDeclaration(nameNode);
varInfo.addRemovable(vanillaForNameDeclaration);
}
}
}
}
private void traverseDeclarationStatement(Node declarationStatement, Scope scope) {
// Normalization should ensure that declaration statements always have just one child.
Node nameNode = declarationStatement.getOnlyChild();
if (!nameNode.isName()) {
// Destructuring declarations are handled elsewhere.
traverseNode(nameNode, scope);
} else {
Node valueNode = nameNode.getFirstChild();
VarInfo varInfo =
traverseVar(checkNotNull(scope.getVar(nameNode.getString())));
RemovableBuilder builder = new RemovableBuilder();
if (valueNode == null) {
varInfo.addRemovable(builder.buildNameDeclarationStatement(declarationStatement));
} else {
if (NodeUtil.mayHaveSideEffects(valueNode)) {
traverseNode(valueNode, scope);
} else {
builder.addContinuation(new Continuation(valueNode, scope));
}
NameDeclarationStatement removable =
builder.setAssignedValue(valueNode).buildNameDeclarationStatement(declarationStatement);
varInfo.addRemovable(removable);
}
}
}
private void traverseAssign(Node assignNode, Scope scope) {
checkState(NodeUtil.isAssignmentOp(assignNode));
Node lhs = assignNode.getFirstChild();
Node nameNode = null;
Node propertyNode = null;
boolean isVariableAssign = false;
boolean isComputedPropertyAssign = false;
boolean isNamedPropertyAssign = false;
boolean isPrototypeObjectPropertyAssignment = false;
if (lhs.isName()) {
isVariableAssign = true;
nameNode = lhs;
} else if (NodeUtil.isGet(lhs)) {
propertyNode = lhs.getLastChild();
Node possibleNameNode = lhs.getFirstChild();
// Handle assignments to properties of a variable or its prototype property.
// However, don't handle any longer qualified names, because it gets hard to track
// properties of properties.
if (possibleNameNode.isGetProp()
&& possibleNameNode.getSecondChild().getString().equals("prototype")) {
isPrototypeObjectPropertyAssignment = true;
possibleNameNode = possibleNameNode.getFirstChild();
}
if (possibleNameNode.isName()) {
nameNode = possibleNameNode;
if (lhs.isGetProp()) {
isNamedPropertyAssign = true;
} else {
checkState(lhs.isGetElem());
isComputedPropertyAssign = true;
}
}
}
// else LHS is something else, like a destructuring pattern, which will be handled by
// traverseChildren() below
// TODO(bradfordcsmith): Handle destructuring at this level for better clarity and so we can
// do a better job with removal.
// If we successfully identified a name node & there is a corresponding Var,
// then we have a removable assignment.
Var var = (nameNode == null) ? null : scope.getVar(nameNode.getString());
if (var == null) {
traverseChildren(assignNode, scope);
} else {
Node valueNode = assignNode.getLastChild();
RemovableBuilder builder =
new RemovableBuilder()
.setAssignedValue(valueNode)
.setIsPrototypeObjectPropertyAssignment(isPrototypeObjectPropertyAssignment);
if (NodeUtil.isExpressionResultUsed(assignNode) || NodeUtil.mayHaveSideEffects(valueNode)) {
traverseNode(valueNode, scope);
} else {
builder.addContinuation(new Continuation(valueNode, scope));
}
VarInfo varInfo = traverseVar(var);
if (isNamedPropertyAssign) {
varInfo.addRemovable(builder.buildNamedPropertyAssign(assignNode, nameNode, propertyNode));
} else if (isVariableAssign) {
varInfo.addRemovable(builder.buildVariableAssign(assignNode, nameNode));
} else {
checkState(isComputedPropertyAssign);
if (NodeUtil.mayHaveSideEffects(propertyNode)) {
traverseNode(propertyNode, scope);
} else {
builder.addContinuation(new Continuation(propertyNode, scope));
}
varInfo.addRemovable(
builder.buildComputedPropertyAssign(assignNode, nameNode, propertyNode));
}
}
}
private void traverseDefaultValue(Node defaultValueNode, Scope scope) {
Var var;
Node target = defaultValueNode.getFirstChild();
Node value = target.getNext();
if (!target.isName()) {
traverseNode(target, scope);
traverseNode(value, scope);
} else {
var = scope.getVar(target.getString());
if (var == null) {
traverseNode(value, scope);
} else {
VarInfo varInfo = traverseVar(var);
if (NodeUtil.mayHaveSideEffects(value)) {
// TODO(johnlenz): we don't really need to retain all uses of the variable, just
// enough to host the default value assignment.
varInfo.markAsReferenced();
traverseNode(value, scope);
} else {
DestructuringAssign assign =
new RemovableBuilder()
.addContinuation(new Continuation(value, scope))
.buildDestructuringAssign(defaultValueNode, target);
varInfo.addRemovable(assign);
}
}
}
}
private void traverseArrayPattern(Node arrayPattern, Scope scope) {
for (Node c = arrayPattern.getFirstChild(); c != null; c = c.getNext()) {
if (!c.isName()) {
// TODO(bradfordcsmith): Treat destructuring assignments to properties as removable writes.
traverseNode(c, scope);
} else {
Var var = scope.getVar(c.getString());
if (var != null) {
VarInfo varInfo = traverseVar(var);
varInfo.addRemovable(new RemovableBuilder().buildDestructuringAssign(c, c));
}
}
}
}
private void traverseObjectPattern(Node objectPattern, Scope scope) {
for (Node propertyNode = objectPattern.getFirstChild();
propertyNode != null;
propertyNode = propertyNode.getNext()) {
traverseObjectPatternElement(propertyNode, scope);
}
}
private void traverseObjectPatternElement(Node elm, Scope scope) {
// non-null for computed properties
// `{[propertyExpression]: target} = ...`
Node propertyExpression = null;
// non-null for named properties
// `{propertyName: target} = ...`
String propertyName = null;
Node target = null;
Node defaultValue = null;
// Get correct values for all the variables above.
if (elm.isComputedProp()) {
propertyExpression = elm.getFirstChild();
target = elm.getLastChild();
} else {
checkState(elm.isStringKey());
target = elm.getOnlyChild();
// Treat `{'a': x} = ...` like `{['a']: x} = ...`, but it never has side-effects and we
// have no propertyExpression to traverse.
// NOTE: The parser will convert `{1: x} = ...` to `{'1': x} = ...`
if (!elm.isQuotedString()) {
propertyName = elm.getString();
}
}
if (target.isDefaultValue()) {
target = target.getFirstChild();
defaultValue = checkNotNull(target.getNext());
}
// TODO(bradfordcsmith): Handle property assignments also
Var var = target.isName() ? scope.getVar(target.getString()) : null;
// TODO(bradfordcsmith): Arrange to safely remove side-effect cases.
boolean cannotRemove =
var == null
|| (propertyExpression != null && NodeUtil.mayHaveSideEffects(propertyExpression))
|| (defaultValue != null && NodeUtil.mayHaveSideEffects(defaultValue));
if (cannotRemove) {
if (propertyExpression != null) {
traverseNode(propertyExpression, scope);
}
if (propertyName != null) {
markPropertyNameReferenced(propertyName);
}
traverseNode(target, scope);
if (defaultValue != null) {
traverseNode(defaultValue, scope);
}
if (var != null) {
// Since we cannot remove it, we must now treat this usage as a reference.
traverseVar(var).markAsReferenced();
}
} else {
RemovableBuilder builder = new RemovableBuilder();
if (propertyName != null) {
// TODO(bradfordcsmith): Use a continuation here.
markPropertyNameReferenced(propertyName);
}
if (propertyExpression != null) {
builder.addContinuation(new Continuation(propertyExpression, scope));
}
if (defaultValue != null) {
builder.addContinuation(new Continuation(defaultValue, scope));
}
traverseVar(var)
.addRemovable(builder.buildDestructuringAssign(elm, target));
}
}
private void traverseChildren(Node n, Scope scope) {
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
traverseNode(c, scope);
}
}
/**
* Handle a class that is not the RHS child of an assignment or a variable declaration
* initializer.
*
* <p>For
* @param classNode
* @param scope
*/
private void traverseClass(Node classNode, Scope scope) {
checkArgument(classNode.isClass());
if (NodeUtil.isClassDeclaration(classNode)) {
traverseClassDeclaration(classNode, scope);
} else {
traverseClassExpression(classNode, scope);
}
}
private void traverseClassDeclaration(Node classNode, Scope scope) {
checkArgument(classNode.isClass());
Node classNameNode = classNode.getFirstChild();
Node baseClassExpression = classNameNode.getNext();
Node classBodyNode = baseClassExpression.getNext();
Scope classScope = scopeCreator.createScope(classNode, scope);
VarInfo varInfo = traverseVar(scope.getVar(classNameNode.getString()));
if (classNode.getParent().isExport()) {
// Cannot remove an exported class.
varInfo.setIsExplicitlyNotRemovable();
traverseNode(baseClassExpression, scope);
// Use traverseChildren() here, because we should not consider any properties on the exported
// class to be removable.
traverseChildren(classBodyNode, classScope);
} else if (NodeUtil.mayHaveSideEffects(baseClassExpression)) {
// TODO(bradfordcsmith): implement removal without losing side-effects for this case
varInfo.setIsExplicitlyNotRemovable();
traverseNode(baseClassExpression, scope);
traverseClassMembers(classBodyNode, classScope);
} else {
RemovableBuilder builder =
new RemovableBuilder()
.addContinuation(new Continuation(baseClassExpression, classScope))
.addContinuation(new Continuation(classBodyNode, classScope));
varInfo.addRemovable(builder.buildClassDeclaration(classNode));
}
}
private void traverseClassExpression(Node classNode, Scope scope) {
checkArgument(classNode.isClass());
Node classNameNode = classNode.getFirstChild();
Node baseClassExpression = classNameNode.getNext();
Node classBodyNode = baseClassExpression.getNext();
Scope classScope = scopeCreator.createScope(classNode, scope);
if (classNameNode.isName()) {
// We may be able to remove the name node if nothing ends up referring to it.
VarInfo varInfo = traverseVar(classScope.getVar(classNameNode.getString()));
varInfo.addRemovable(new RemovableBuilder().buildNamedClassExpression(classNode));
}
// If we're traversing the class expression, we've already decided we cannot remove it.
traverseNode(baseClassExpression, scope);
traverseClassMembers(classBodyNode, classScope);
}
private void traverseClassMembers(Node node, Scope scope) {
checkArgument(node.isClassMembers(), node);
if (removeUnusedProperties) {
for (Node member = node.getFirstChild(); member != null; member = member.getNext()) {
if (member.isMemberFunctionDef() || NodeUtil.isGetOrSetKey(member)) {
// If we get as far as traversing the members of a class, we've already decided that
// we cannot remove the class itself, so just consider individual members for removal.
considerForIndependentRemoval(
new RemovableBuilder()
.addContinuation(new Continuation(member, scope))
.buildMethodDefinition(member));
} else {
checkState(member.isComputedProp());
traverseChildren(member, scope);
}
}
} else {
traverseChildren(node, scope);
}
}
/**
* Traverses a function
*
* ES6 scopes of a function include the parameter scope and the body scope
* of the function.
*
* Note that CATCH blocks also create a new scope, but only for the
* catch variable. Declarations within the block actually belong to the
* enclosing scope. Because we don't remove catch variables, there's
* no need to treat CATCH blocks differently like we do functions.
*/
private void traverseFunction(Node function, Scope parentScope) {
checkState(function.getChildCount() == 3, function);
checkState(function.isFunction(), function);
final Node paramlist = NodeUtil.getFunctionParameters(function);
final Node body = function.getLastChild();
checkState(body.getNext() == null && body.isNormalBlock(), body);
// Checking the parameters
Scope fparamScope = scopeCreator.createScope(function, parentScope);
// Checking the function body
Scope fbodyScope = scopeCreator.createScope(body, fparamScope);
String name = function.getFirstChild().getString();
if (!name.isEmpty()) {
// var x = function funcName() {};
Var var = checkNotNull(fparamScope.getVar(name));
// make sure funcName gets into the varInfoMap so it will be considered for removal.
traverseVar(var);
}
traverseChildren(paramlist, fparamScope);
traverseChildren(body, fbodyScope);
allFunctionParamScopes.add(fparamScope);
}
private boolean canRemoveParameters(Node parameterList) {
checkState(parameterList.isParamList());
Node function = parameterList.getParent();
return removeGlobals && !NodeUtil.isGetOrSetKey(function.getParent());
}
/**
* Removes unreferenced arguments from a function declaration and when
* possible the function's callSites.
*
* @param fparamScope The function parameter
*/
private void removeUnreferencedFunctionArgs(Scope fparamScope) {
// Notice that removing unreferenced function args breaks
// Function.prototype.length. In advanced mode, we don't really care
// about this: we consider "length" the equivalent of reflecting on
// the function's lexical source.
//
// Rather than create a new option for this, we assume that if the user
// is removing globals, then it's OK to remove unused function args.
//
// See http://blickly.github.io/closure-compiler-issues/#253
if (!removeGlobals) {
return;
}
Node function = fparamScope.getRootNode();
checkState(function.isFunction());
if (NodeUtil.isGetOrSetKey(function.getParent())) {
// The parameters object literal setters can not be removed.
return;
}
Node argList = NodeUtil.getFunctionParameters(function);
// Strip as many unreferenced args off the end of the function declaration as possible.
maybeRemoveUnusedTrailingParameters(argList, fparamScope);
// Mark any remaining unused parameters are unused to OptimizeParameters can try to remove
// them.
markUnusedParameters(argList, fparamScope);
}
private void markPropertyNameReferenced(String propertyName) {
if (referencedPropertyNames.add(propertyName)) {
// Continue traversal of all of the property name's values and no longer consider them for
// removal.
for (Removable removable : removablesForPropertyNames.removeAll(propertyName)) {
removable.applyContinuations();
}
}
}
private void considerForIndependentRemoval(Removable removable) {
if (removeUnusedProperties && removable.isNamedProperty()) {
String propertyName = removable.getPropertyName();
if (referencedPropertyNames.contains(propertyName)
|| codingConvention.isExported(propertyName)) {
// Referenced, so not removable.
removable.applyContinuations();
} else if (removable.isIndependentlyRemovableNamedProperty()) {
// Store for possible removal later.
removablesForPropertyNames.put(removable.getPropertyName(), removable);
} else {
// TODO(bradfordcsmith): Maybe allow removal of non-prototype property assignments if we
// can be sure the variable's value is defined as a literal value that does not escape.
removable.applyContinuations();
// This assignment counts as a reference, since we won't be removing it.
// This is necessary in order to preserve getters and setters for the property.
markPropertyNameReferenced(propertyName);
}
} else {
removable.applyContinuations();
}
}
/**
* Mark any remaining unused parameters as being unused so it can be used elsewhere.
*
* @param paramList list of function's parameters
* @param fparamScope
*/
private void markUnusedParameters(Node paramList, Scope fparamScope) {
for (Node param = paramList.getFirstChild(); param != null; param = param.getNext()) {
if (!param.isUnusedParameter()) {
Node lValue = param;
if (lValue.isDefaultValue()) {
lValue = lValue.getFirstChild();
}
if (lValue.isRest()) {
lValue = lValue.getOnlyChild();
}
if (lValue.isDestructuringPattern()) {
continue;
}
Var var = fparamScope.getVar(lValue.getString());
VarInfo varInfo = getVarInfo(var);
if (varInfo.isRemovable()) {
param.setUnusedParameter(true);
compiler.reportChangeToEnclosingScope(paramList);
}
}
}
}
/**
* Strip as many unreferenced args off the end of the function declaration as possible. We start
* from the end of the function declaration because removing parameters from the middle of the
* param list could mess up the interpretation of parameters being sent over by any function
* calls.
*
* @param argList list of function's arguments
* @param fparamScope
*/
private void maybeRemoveUnusedTrailingParameters(Node argList, Scope fparamScope) {
Node lastArg;
while ((lastArg = argList.getLastChild()) != null) {
Node lValue = lastArg;
if (lastArg.isDefaultValue()) {
lValue = lastArg.getFirstChild();
if (NodeUtil.mayHaveSideEffects(lastArg.getLastChild())) {
break;
}
}
if (lValue.isRest()) {
lValue = lValue.getFirstChild();
}
if (lValue.isDestructuringPattern()) {
if (lValue.hasChildren()) {
// TODO(johnlenz): handle the case where there are no assignments.
break;
} else {
// Remove empty destructuring patterns and their associated object literal assignment
// if it exists and if the right hand side does not have side effects. Note, a
// destructuring pattern with a "leftover" property key as in {a:{}} is not considered
// empty in this case!
NodeUtil.deleteNode(lastArg, compiler);
continue;
}
}
Var var = fparamScope.getVar(lValue.getString());
VarInfo varInfo = getVarInfo(var);