com.android.tools.lint.checks.AssertDetector Maven / Gradle / Ivy
/*
* Copyright (C) 2014 The Android Open Source Project
*
* 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.android.tools.lint.checks;
import com.android.annotations.NonNull;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.Context;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Implementation;
import com.android.tools.lint.detector.api.Issue;
import com.android.tools.lint.detector.api.JavaContext;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import java.io.File;
import java.util.Collections;
import java.util.List;
import lombok.ast.Assert;
import lombok.ast.AstVisitor;
import lombok.ast.BinaryExpression;
import lombok.ast.BooleanLiteral;
import lombok.ast.Expression;
import lombok.ast.ForwardingAstVisitor;
import lombok.ast.Node;
import lombok.ast.NullLiteral;
/**
* Looks for assertion usages.
*/
public class AssertDetector extends Detector implements Detector.JavaScanner {
/** Using assertions */
public static final Issue ISSUE = Issue.create(
"Assert", //$NON-NLS-1$
"Assertions",
"Assertions are not checked at runtime. There are ways to request that they be used " +
"by Dalvik (`adb shell setprop debug.assert 1`), but the property is ignored in " +
"many places and can not be relied upon. Instead, perform conditional checking " +
"inside `if (BuildConfig.DEBUG) { }` blocks. That constant is a static final boolean " +
"which is true in debug builds and false in release builds, and the Java compiler " +
"completely removes all code inside the if-body from the app.\n" +
"\n" +
"For example, you can replace `assert speed > 0` with " +
"`if (BuildConfig.DEBUG && !(speed > 0)) { throw new AssertionError() }`.\n" +
"\n" +
"(Note: This lint check does not flag assertions purely asserting nullness or " +
"non-nullness; these are typically more intended for tools usage than runtime " +
"checks.)",
Category.CORRECTNESS,
6,
Severity.WARNING,
new Implementation(
AssertDetector.class,
Scope.JAVA_FILE_SCOPE))
.addMoreInfo(
"https://code.google.com/p/android/issues/detail?id=65183"); //$NON-NLS-1$
/** Constructs a new {@link com.android.tools.lint.checks.AssertDetector} check */
public AssertDetector() {
}
@Override
public boolean appliesTo(@NonNull Context context, @NonNull File file) {
return true;
}
// ---- Implements JavaScanner ----
@Override
public List> getApplicableNodeTypes() {
return Collections.>singletonList(Assert.class);
}
@Override
public AstVisitor createJavaVisitor(@NonNull final JavaContext context) {
return new ForwardingAstVisitor() {
@Override
public boolean visitAssert(Assert node) {
Expression assertion = node.astAssertion();
// Allow "assert true"; it's basically a no-op
if (assertion instanceof BooleanLiteral) {
Boolean b = ((BooleanLiteral) assertion).astValue();
if (b != null && b) {
return false;
}
} else {
// Allow assertions of the form "assert foo != null" because they are often used
// to make statements to tools about known nullness properties. For example,
// findViewById() may technically return null in some cases, but a developer
// may know that it won't be when it's called correctly, so the assertion helps
// to clear nullness warnings.
if (isNullCheck(assertion)) {
return false;
}
}
String message
= "Assertions are unreliable. Use `BuildConfig.DEBUG` conditional checks instead.";
context.report(ISSUE, node, context.getLocation(node), message);
return false;
}
};
}
/**
* Checks whether the given expression is purely a non-null check, e.g. it will return
* true for expressions like "a != null" and "a != null && b != null" and
* "b == null || c != null".
*/
private static boolean isNullCheck(Expression expression) {
if (expression instanceof BinaryExpression) {
BinaryExpression binExp = (BinaryExpression) expression;
if (binExp.astLeft() instanceof NullLiteral ||
binExp.astRight() instanceof NullLiteral) {
return true;
} else {
return isNullCheck(binExp.astLeft()) && isNullCheck(binExp.astRight());
}
} else {
return false;
}
}
}