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 static com.android.tools.lint.detector.api.LintUtils.isNullLiteral;
import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Detector.JavaPsiScanner;
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 com.intellij.psi.JavaElementVisitor;
import com.intellij.psi.PsiAssertStatement;
import com.intellij.psi.PsiBinaryExpression;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiExpression;
import com.intellij.psi.PsiLiteral;
import java.util.Collections;
import java.util.List;
/**
* Looks for assertion usages.
*/
public class AssertDetector extends Detector implements JavaPsiScanner {
/** 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 AssertDetector} check */
public AssertDetector() {
}
// ---- Implements JavaScanner ----
@Override
public List> getApplicablePsiTypes() {
return Collections.>singletonList(PsiAssertStatement.class);
}
@Nullable
@Override
public JavaElementVisitor createPsiVisitor(@NonNull final JavaContext context) {
if (!context.getMainProject().isAndroidProject()) {
return null;
}
return new JavaElementVisitor() {
@Override
public void visitAssertStatement(PsiAssertStatement node) {
PsiExpression assertion = node.getAssertCondition();
// Allow "assert true"; it's basically a no-op
if (assertion instanceof PsiLiteral) {
Object value = ((PsiLiteral)assertion).getValue();
if (Boolean.TRUE.equals(value)) {
return;
}
} 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;
}
}
String message
= "Assertions are unreliable. Use `BuildConfig.DEBUG` conditional checks instead.";
context.report(ISSUE, node, context.getLocation(node), message);
}
};
}
/**
* 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(PsiExpression expression) {
if (expression instanceof PsiBinaryExpression) {
PsiBinaryExpression binExp = (PsiBinaryExpression) expression;
PsiExpression lOperand = binExp.getLOperand();
PsiExpression rOperand = binExp.getROperand();
if (isNullLiteral(lOperand) || isNullLiteral(rOperand)) {
return true;
} else {
return isNullCheck(lOperand) && isNullCheck(rOperand);
}
} else {
return false;
}
}
}