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Liferay Frontend JS Minifier
/*
* Copyright 2016 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.checkState;
import com.google.javascript.jscomp.colors.Color;
import com.google.javascript.jscomp.colors.StandardColors;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
/** An optimization pass to re-write J2CL Equality.$same. */
public class J2clEqualitySameRewriterPass extends AbstractPeepholeOptimization {
private final boolean useTypes;
private boolean shouldRunJ2clPasses;
J2clEqualitySameRewriterPass(boolean useTypes) {
this.useTypes = useTypes;
}
@Override
void beginTraversal(AbstractCompiler compiler) {
super.beginTraversal(compiler);
shouldRunJ2clPasses = J2clSourceFileChecker.shouldRunJ2clPasses(compiler);
}
@Override
Node optimizeSubtree(Node node) {
if (!shouldRunJ2clPasses) {
return node;
}
// Do not optimize if any parameters were removed during optimizations
if (!node.hasXChildren(3)) {
return node;
}
Node replacement = null;
if (isStringEqualsMethod(node)) {
replacement = trySubstituteStringEquals(node);
} else if (isEqualitySameCall(node)) {
replacement = trySubstituteEqualitySame(node);
}
if (replacement == null) {
return node;
}
replacement.srcrefIfMissing(node);
node.replaceWith(replacement);
reportChangeToEnclosingScope(replacement);
return replacement;
}
private Node trySubstituteStringEquals(Node callNode) {
NodeValue firstExprValue = getKnownLiteralValue(callNode.getSecondChild());
if (firstExprValue == NodeValue.UNKNOWN || firstExprValue == NodeValue.NULL_OR_UNDEFINED) {
// Potential NPE, don't optimize.
return null;
}
return trySubstituteEqualitySame(callNode);
}
private Node trySubstituteEqualitySame(Node callNode) {
Node firstExpr = callNode.getSecondChild();
NodeValue firstExprValue = getKnownLiteralValue(firstExpr);
Node secondExpr = callNode.getLastChild();
NodeValue secondExprValue = getKnownLiteralValue(secondExpr);
if (firstExprValue == NodeValue.UNKNOWN && secondExprValue == NodeValue.UNKNOWN) {
return null;
}
if (firstExprValue == NodeValue.NULL_OR_UNDEFINED) {
return rewriteNullCheck(secondExpr, firstExpr);
}
if (secondExprValue == NodeValue.NULL_OR_UNDEFINED) {
return rewriteNullCheck(firstExpr, secondExpr);
}
if (firstExprValue == NodeValue.NON_NULL || secondExprValue == NodeValue.NON_NULL) {
// There is a coercion danger (e.g. 0 == null) but since at least one side is not null, we can
// safely use === that will not trigger any coercion.
return rewriteAsStrictEq(firstExpr, secondExpr);
}
checkState(firstExprValue == NodeValue.NUMBER || secondExprValue == NodeValue.NUMBER);
return rewriteNumberCheck(firstExpr, secondExpr);
}
private Node rewriteNullCheck(Node expr, Node nullExpression) {
expr.detach();
nullExpression.detach();
if (useTypes && canOnlyBeObject(expr)) {
return IR.not(expr);
}
// At least one side is null or undefined so no coercion danger with ==.
return IR.eq(expr, nullExpression);
}
private boolean canOnlyBeObject(Node n) {
Color color = n.getColor();
// Safe as long as the color is a) not the UNKNOWN native color and b) not any primitive
if (color == null) {
return false;
}
if (color.isUnion()) {
// ignore null/undefined
color = color.subtractNullOrVoid();
}
// In theory we could allow unions of multiple objects here
return !color.isUnion() && !color.isPrimitive() && !color.equals(StandardColors.UNKNOWN);
}
private Node rewriteAsStrictEq(Node firstExpr, Node secondExpr) {
firstExpr.detach();
secondExpr.detach();
return IR.sheq(firstExpr, secondExpr);
}
private Node rewriteNumberCheck(Node firstExpr, Node secondExpr) {
Double firstValue = NodeUtil.getNumberValue(firstExpr);
Double secondValue = NodeUtil.getNumberValue(secondExpr);
if (firstValue != null && secondValue != null) {
firstExpr.detach();
secondExpr.detach();
return NodeUtil.booleanNode(firstValue.equals(secondValue));
}
if (isSafeNumber(firstValue) || isSafeNumber(secondValue)) {
// Since one side is not 0, -0 or NaN, there is no risk of -0 vs 0 or NaN vs NaN comparison.
return rewriteAsStrictEq(firstExpr, secondExpr);
}
if (useTypes && (canOnlyBeObject(firstExpr) || canOnlyBeObject(secondExpr))) {
// Since one side is not number, there is no risk of -0 vs 0 or NaN vs NaN comparision.
return rewriteAsStrictEq(firstExpr, secondExpr);
}
return null;
}
private static boolean isSafeNumber(Double d) {
return d != null && d != 0 && !d.isNaN();
}
private enum NodeValue {
UNKNOWN,
NULL_OR_UNDEFINED,
// JavaScript number. Needs special treatment to preserve Object.is semantics.
NUMBER,
// Non-null and also known to be not a number.
NON_NULL,
}
private static NodeValue getKnownLiteralValue(Node n) {
switch (NodeUtil.getKnownValueType(n)) {
case VOID:
return NodeUtil.canBeSideEffected(n) ? NodeValue.UNKNOWN : NodeValue.NULL_OR_UNDEFINED;
case NULL:
return NodeValue.NULL_OR_UNDEFINED;
case STRING:
case BOOLEAN:
case OBJECT:
case BIGINT:
return NodeValue.NON_NULL;
case NUMBER:
return NodeValue.NUMBER;
case UNDETERMINED:
return NodeValue.UNKNOWN;
}
throw new AssertionError("Unknown ValueType");
}
private static boolean isEqualitySameCall(Node node) {
return node.isCall() && hasName(node.getFirstChild(), "Equality", "$same");
}
private static boolean isStringEqualsMethod(Node node) {
return node.isCall()
&& hasName(node.getFirstChild(), "String", "m_equals__java_lang_String__java_lang_Object");
}
private static boolean hasName(Node fnName, String className, String methodName) {
if (!fnName.isQualifiedName()) {
return false;
}
// NOTE: This should be rewritten to use method name + file name of definition site
// like other J2CL passes, which is more precise.
String originalQname = fnName.getOriginalQualifiedName();
return originalQname.endsWith(methodName) && originalQname.contains(className);
}
}