/*
* Copyright 2015 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 com.google.common.base.Preconditions;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.JSDocInfo.Visibility;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.TypeI;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* This pass looks for properties that are never read.
* These can be properties created using "this", or static properties of
* constructors or interfaces. Explicitly ignored is the possibility that
* these properties may be indirectly referenced using "for-in" or
* "Object.keys".
*
* This class is based on RemoveUnusedClassProperties, some effort should
* be made to extract the common pieces.
*
* @author johnlenz@google.com (John Lenz)
*/
class CheckUnusedPrivateProperties
implements HotSwapCompilerPass, NodeTraversal.Callback {
static final DiagnosticType UNUSED_PRIVATE_PROPERTY =
DiagnosticType.disabled(
"JSC_UNUSED_PRIVATE_PROPERTY", "Private property {0} is never read");
private final AbstractCompiler compiler;
private Set<String> used = new HashSet<>();
private List<Node> candidates = new ArrayList<>();
CheckUnusedPrivateProperties(AbstractCompiler compiler) {
this.compiler = compiler;
}
@Override
public void process(Node externs, Node root) {
NodeTraversal.traverseEs6(compiler, root, this);
}
@Override
public void hotSwapScript(Node scriptRoot, Node originalRoot) {
NodeTraversal.traverseEs6(compiler, scriptRoot, this);
}
private void reportUnused(NodeTraversal t) {
for (Node n : candidates) {
String propName = getPropName(n);
if (!used.contains(propName)) {
t.report(n, UNUSED_PRIVATE_PROPERTY, propName);
}
}
}
private String getPropName(Node n) {
switch (n.getToken()) {
case GETPROP:
return n.getLastChild().getString();
case MEMBER_FUNCTION_DEF:
return n.getString();
default:
break;
}
throw new RuntimeException("Unexpected node type: " + n);
}
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
if (n.isScript()) {
used.clear();
candidates.clear();
}
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case SCRIPT: {
// exiting the script, report any privates not used in the file.
reportUnused(t);
break;
}
case GETPROP: {
String propName = n.getLastChild().getString();
if (compiler.getCodingConvention().isExported(propName)
|| isPinningPropertyUse(n)
|| !isCandidatePropertyDefinition(n)) {
used.add(propName);
} else {
// Only consider "private" properties.
if (isCheckablePrivatePropDecl(n)) {
candidates.add(n);
}
}
break;
}
case MEMBER_FUNCTION_DEF: {
// Only consider "private" methods.
if (isCheckablePrivatePropDecl(n)) {
candidates.add(n);
}
break;
}
case OBJECTLIT: {
// Assume any object literal definition might be a reflection on the
// class property.
for (Node c : n.children()) {
used.add(c.getString());
}
break;
}
case CALL:
// Look for properties referenced through a property rename function.
Node target = n.getFirstChild();
if (n.hasMoreThanOneChild()
&& compiler
.getCodingConvention()
.isPropertyRenameFunction(target.getOriginalQualifiedName())) {
Node propName = target.getNext();
if (propName.isString()) {
used.add(propName.getString());
}
}
break;
default:
break;
}
}
private boolean isPrivatePropDecl(Node n) {
// TODO(johnlenz): add support private by convention property definitions without JSDoc.
// TODO(johnlenz): add support for checking protected properties in final classes
// TODO(johnlenz): add support for checking "package" properties when checking an entire
// library.
JSDocInfo info = NodeUtil.getBestJSDocInfo(n);
return (info != null && info.getVisibility() == Visibility.PRIVATE);
}
private boolean isCheckablePrivatePropDecl(Node n) {
// TODO(tbreisacher): Look for uses of the typedef/interface in type expressions; warn if there
// are no uses.
JSDocInfo info = NodeUtil.getBestJSDocInfo(n);
return isPrivatePropDecl(n) && !info.hasTypedefType() && !info.isInterface();
}
private boolean isCandidatePropertyDefinition(Node n) {
Preconditions.checkState(n.isGetProp(), n);
Node target = n.getFirstChild();
return target.isThis()
|| (isConstructor(target))
|| (target.isGetProp()
&& target.getLastChild().getString().equals("prototype"));
}
private boolean isConstructor(Node n) {
// If type checking is enabled (not just a per-file lint check),
// we can check constructor properties too. But it isn't required.
TypeI type = n.getTypeI();
return type != null && (type.isConstructor() || type.isInterface());
}
/**
* @return Whether the property is used in a way that prevents its removal.
*/
private static boolean isPinningPropertyUse(Node n) {
// Rather than looking for cases that are uses, we assume all references are
// pinning uses unless they are:
// - a simple assignment (x.a = 1)
// - a compound assignment or increment (x++, x += 1) whose result is
// otherwise unused
Node parent = n.getParent();
if (n == parent.getFirstChild()) {
if (parent.isExprResult()) {
// A stub declaration "this.x;" isn't a pinning use.
return false;
} else if (parent.isAssign()) {
// A simple assignment doesn't pin the property.
return false;
} else if (NodeUtil.isAssignmentOp(parent)
|| parent.isInc() || parent.isDec()) {
// In general, compound assignments are both reads and writes, but
// if the property is never otherwise read we can consider it simply
// a write.
// However if the assign expression is used as part of a larger
// expression, we must consider it a read. For example:
// x = (y.a += 1);
return NodeUtil.isExpressionResultUsed(parent);
}
}
return true;
}
}