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RemoveUnusedCode: Remove Object.defineProperties(unusedVar, ...
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Also do a little bit of code clean up.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183721363
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@brad4d @lauraharker
brad4d authored and lauraharker committed Jan 30, 2018
1 parent e2ff7ef commit d04416a
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Showing 2 changed files with 90 additions and 62 deletions.
85 changes: 59 additions & 26 deletions src/com/google/javascript/jscomp/RemoveUnusedCode.java
View file
Expand Up @@ -593,19 +593,28 @@ private void traverseObjectDefinePropertiesCall(Node callNode, Scope scope) {
Node callee = callNode.getFirstChild();
Node targetObject = callNode.getSecondChild();
Node propertyDefinitions = targetObject.getNext();
// TODO(bradfordcsmith): It should be possible to remove the entire Object.defineProperties()
// call if the target object is otherwise unused and evaluating the property definitions object
// has no side-effects.
// TODO(bradfordcsmith): If the affected object is a variable reference, this should be
// considered a variable assignment similar to a goog.inherits() call, so it won't block removal
// of the variable.
traverseNode(callee, scope);
traverseNode(targetObject, scope);
if (propertyDefinitions.isObjectLit()) {
// TODO(bradfordcsmith): Consider restricting special handling of the properties literal to
// cases where the target object is a known class, prototype, or this.
traverseObjectDefinePropertiesLiteral(propertyDefinitions, scope);

if ((targetObject.isName() || isNameDotPrototype(targetObject))
&& !NodeUtil.isExpressionResultUsed(callNode)) {
// NOTE: Object.defineProperties() returns its first argument, so if its return value is used
// that counts as a use of the targetObject.
Node nameNode = targetObject.isName() ? targetObject : targetObject.getFirstChild();
VarInfo varInfo = traverseNameNode(nameNode, scope);
RemovableBuilder builder = new RemovableBuilder();
// TODO(bradfordcsmith): Is it really necessary to traverse the callee
// (aka. Object.defineProperties)?
builder.addContinuation(new Continuation(callee, scope));
if (NodeUtil.mayHaveSideEffects(propertyDefinitions)) {
traverseNode(propertyDefinitions, scope);
} else {
builder.addContinuation(new Continuation(propertyDefinitions, scope));
}
varInfo.addRemovable(builder.buildClassSetupCall(callNode));
} else {
// TODO(bradfordcsmith): Is it really necessary to traverse the callee
// (aka. Object.defineProperties)?
traverseNode(callee, scope);
traverseNode(targetObject, scope);
traverseNode(propertyDefinitions, scope);
}
}
Expand Down Expand Up @@ -663,11 +672,20 @@ private void traverseObjectLiteral(Node objectLiteral, Scope scope) {
// Is this an object literal that is assigned directly to a 'prototype' property?
if (isAssignmentToPrototype(objectLiteral.getParent())) {
traversePrototypeLiteral(objectLiteral, scope);
} else if (isObjectDefinePropertiesSecondArgument(objectLiteral)) {
// TODO(bradfordcsmith): Consider restricting special handling of the properties literal to
// cases where the target object is a known class, prototype, or this.
traverseObjectDefinePropertiesLiteral(objectLiteral, scope);
} else {
traverseNonPrototypeObjectLiteral(objectLiteral, scope);
}
}

private boolean isObjectDefinePropertiesSecondArgument(Node n) {
Node parent = n.getParent();
return NodeUtil.isObjectDefinePropertiesDefinition(parent) && parent.getLastChild() == n;
}

private void traverseNonPrototypeObjectLiteral(Node objectLiteral, Scope scope) {
for (Node propertyNode = objectLiteral.getFirstChild();
propertyNode != null;
Expand Down Expand Up @@ -806,7 +824,6 @@ private void traverseVanillaForNameDeclarations(Node nameDeclaration, Scope scop
} else {
VanillaForNameDeclaration vanillaForNameDeclaration =
new RemovableBuilder()
.setAssignedValue(valueNode)
.addContinuation(new Continuation(valueNode, scope))
.buildVanillaForNameDeclaration(nameNode);
varInfo.addRemovable(vanillaForNameDeclaration);
Expand Down Expand Up @@ -834,7 +851,7 @@ private void traverseDeclarationStatement(Node declarationStatement, Scope scope
builder.addContinuation(new Continuation(valueNode, scope));
}
NameDeclarationStatement removable =
builder.setAssignedValue(valueNode).buildNameDeclarationStatement(declarationStatement);
builder.buildNameDeclarationStatement(declarationStatement);
varInfo.addRemovable(removable);
}
}
Expand Down Expand Up @@ -924,7 +941,6 @@ private void traverseAssign(Node assignNode, Scope scope) {
}

private void traverseRemovableAssignValue(Node valueNode, RemovableBuilder builder, Scope scope) {
builder.setAssignedValue(valueNode);
if (NodeUtil.mayHaveSideEffects(valueNode)
|| NodeUtil.isExpressionResultUsed(valueNode.getParent())) {
traverseNode(valueNode, scope);
Expand Down Expand Up @@ -1520,7 +1536,6 @@ private abstract class Removable {

private final List<Continuation> continuations;
@Nullable private final String propertyName;
@Nullable private final Node assignedValue;
private final boolean isPrototypeDotPropertyReference;
private final boolean isThisDotPropertyReference;

Expand All @@ -1530,7 +1545,6 @@ private abstract class Removable {
Removable(RemovableBuilder builder) {
continuations = builder.continuations;
propertyName = builder.propertyName;
assignedValue = builder.assignedValue;
isPrototypeDotPropertyReference = builder.isPrototypeDotPropertyReference;
isThisDotPropertyReference = builder.isThisDotPropertyReference;
}
Expand Down Expand Up @@ -1640,7 +1654,6 @@ private class RemovableBuilder {
final List<Continuation> continuations = new ArrayList<>();

@Nullable String propertyName = null;
@Nullable public Node assignedValue = null;
boolean isPrototypeDotPropertyReference = false;
boolean isThisDotPropertyReference = false;

Expand All @@ -1649,11 +1662,6 @@ RemovableBuilder addContinuation(Continuation continuation) {
return this;
}

RemovableBuilder setAssignedValue(@Nullable Node assignedValue) {
this.assignedValue = assignedValue;
return this;
}

RemovableBuilder setIsPrototypeDotPropertyReference(boolean value) {
this.isPrototypeDotPropertyReference = value;
return this;
Expand Down Expand Up @@ -1701,12 +1709,10 @@ NameDeclarationStatement buildNameDeclarationStatement(Node declarationStatement

Assign buildNamedPropertyAssign(Node assignNode, Node propertyNode) {
this.propertyName = propertyNode.getString();
checkNotNull(assignedValue);
return new Assign(this, assignNode, Kind.NAMED_PROPERTY, propertyNode);
}

Assign buildComputedPropertyAssign(Node assignNode, Node propertyNode) {
checkNotNull(assignedValue);
return new Assign(this, assignNode, Kind.COMPUTED_PROPERTY, propertyNode);
}

Expand Down Expand Up @@ -2313,9 +2319,29 @@ private class ClassSetupCall extends Removable {
@Override
public void removeInternal(AbstractCompiler compiler) {
Node parent = callNode.getParent();

Node replacement = null;
// Need to keep call args that have side effects.
// Easiest thing to do is break apart the call node as we go.
// First child is the callee (aka. Object.defineProperties or equivalent)
callNode.removeFirstChild();
for (Node arg = callNode.getLastChild(); arg != null; arg = callNode.getLastChild()) {
arg.detach();
if (NodeUtil.mayHaveSideEffects(arg)) {
if (replacement == null) {
replacement = arg;
} else {
replacement = IR.comma(arg, replacement).srcref(callNode);
}
} else {
NodeUtil.markFunctionsDeleted(arg, compiler);
}
}
// NOTE: The call must either be its own statement or the LHS of a comma expression,
// because it doesn't have a meaningful return value.
if (parent.isExprResult()) {
if (replacement != null) {
replaceNodeWith(callNode, replacement);
} else if (parent.isExprResult()) {
NodeUtil.deleteNode(parent, compiler);
} else {
// `(goog.inherits(A, B), something)` -> `something`
Expand All @@ -2325,6 +2351,13 @@ public void removeInternal(AbstractCompiler compiler) {
parent.replaceWith(rhs.detach());
}
}

@Override
public boolean preventsRemovalOfVariableWithNonLocalValueOrPrototype() {
// If we aren't sure where X comes from and what aliases it might have, we cannot be sure
// it's safe to remove the class setup for it.
return true;
}
}

private static boolean alreadyRemoved(Node n) {
Expand Down
67 changes: 31 additions & 36 deletions test/com/google/javascript/jscomp/RemoveUnusedCodeNameAnalyzerTest.java
View file
Expand Up @@ -1982,6 +1982,11 @@ public void testSingletonGetter3() {
testSame("function Foo() {} goog$addSingletonGetter(Foo); Foo.getInstance();");
}

public void testObjectDefineProperty() {
// TODO(bradfordcsmith): Remove Object.defineProperty() like we do Object.defineProperties().
testSame("var a = {}; Object.defineProperty(a, 'prop', {value: 5});");
}

public void testObjectDefinePropertiesOnNamespaceThatEscapes() {
testSame("var a = doThing1(); Object.defineProperties(a, {'prop': {value: 5}});");
}
Expand All @@ -1999,25 +2004,24 @@ public void testRegularAssignPropOnPropFromAVar() {
testSame("var b = 5; var a = {}; a.prop = b; use(a.prop);");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestUnanalyzableObjectDefineProperties() {
testSame("var a = {}; Object.defineProperties(a, externfoo);");
public void testUnanalyzableObjectDefineProperties() {
test("var a = {}; Object.defineProperties(a, externfoo);", "");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnNamespace1() {
public void testObjectDefinePropertiesOnNamespace1() {
testSame("var a = {}; Object.defineProperties(a, {prop: {value: 5}}); use(a.prop);");
test("var a = {}; Object.defineProperties(a, {prop: {value: 5}});", "");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnNamespace2() {
// Note that since we try to remove the entire Object.defineProperties call whole hog,
// we can't remove a single property from the object literal.
testSame(
public void testObjectDefinePropertiesOnNamespace2() {
test(
lines(
"var a = {};",
"Object.defineProperties(a, {p1: {value: 5}, p2: {value: 3} });",
"use(a.p1);"),
lines(
"var a = {};",
"Object.defineProperties(a, {p1: {value: 5} });",
"use(a.p1);"));

test(
Expand All @@ -2031,8 +2035,7 @@ public void testNonAnalyzableObjectDefinePropertiesCall() {
testSame("var a = {}; var z = Object.defineProperties(a, {'prop': {value: 5}}); use(z);");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnNamespace3() {
public void testObjectDefinePropertiesOnNamespace3() {
testSame(
"var b = 5;"
+ "var a = {};"
Expand All @@ -2047,17 +2050,16 @@ public void disabledTestObjectDefinePropertiesOnNamespace3() {
"var b = 5; use(b);");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnNamespace4() {
public void testObjectDefinePropertiesOnNamespace4() {
test(
"function b() { alert('hello'); };"
+ "var a = {};"
+ "Object.defineProperties(a, {prop: {value: b()}});",
"function b() { alert('hello'); }; b()");
lines(
"function b() { alert('hello'); };",
"var a = {};",
"Object.defineProperties(a, {prop: {value: b()}});"),
"function b() { alert('hello'); }; ({prop: {value: b()}});");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnNamespace5() {
public void testObjectDefinePropertiesOnNamespace5() {
test(
lines(
"function b() { alert('hello'); };", // preserve newline
Expand All @@ -2068,17 +2070,15 @@ public void disabledTestObjectDefinePropertiesOnNamespace5() {
"function b() { alert('hello'); };", // preserve newline
"function c() { alert('world'); };",
" ",
"b(); c();"));
" ({p1: {value: b()}, p2: {value: c()}});"));
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnConstructor() {
public void testObjectDefinePropertiesOnConstructor() {
testSame("function Foo() {} Object.defineProperties(Foo, {prop: {value: 5}}); use(Foo.prop);");
test("function Foo() {} Object.defineProperties(Foo, {prop: {value: 5}});", "");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnPrototype1() {
public void testObjectDefinePropertiesOnPrototype1() {
testSame(
"function Foo() {}"
+ "Object.defineProperties(Foo.prototype, {prop: {value: 5}});"
Expand All @@ -2087,8 +2087,7 @@ public void disabledTestObjectDefinePropertiesOnPrototype1() {
test("function Foo() {} Object.defineProperties(Foo.prototype, {prop: {value: 5}});", "");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnPrototype2() {
public void testObjectDefinePropertiesOnPrototype2() {
test(
lines(
"var b = 5;",
Expand All @@ -2098,36 +2097,32 @@ public void disabledTestObjectDefinePropertiesOnPrototype2() {
"var b = 5; use(b);");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefinePropertiesOnPrototype3() {
public void testObjectDefinePropertiesOnPrototype3() {
test(
lines(
"var b = function() {};",
"function Foo() {}",
"Object.defineProperties(Foo.prototype, {prop: {value: b()}});"),
"var b = function() {}; b();");
"var b = function() {}; ({prop: {value: b()}});");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefineGetters() {
public void testObjectDefineGetters() {
test("function Foo() {} Object.defineProperties(Foo, {prop: {get: function() {}}});", "");

test(
"function Foo() {} Object.defineProperties(Foo.prototype, {prop: {get: function() {}}});",
"");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefineSetters() {
public void testObjectDefineSetters() {
test("function Foo() {} Object.defineProperties(Foo, {prop: {set: function() {}}});", "");

test(
"function Foo() {} Object.defineProperties(Foo.prototype, {prop: {set: function() {}}});",
"");
}

// TODO(b/66971163): implement removal of defineProperties() when object is unused
public void disabledTestObjectDefineSetters_global() {
public void testObjectDefineSetters_global() {
test(
lines(
"function Foo() {} ",
Expand Down

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