/*
* Copyright 2014 Google Inc. All Rights Reserved.
*
* 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.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.Category.JDK;
import static com.google.errorprone.BugPattern.MaturityLevel.EXPERIMENTAL;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.SwitchTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.CaseTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.SwitchTree;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import com.sun.tools.javac.tree.JCTree.JCSwitch;
import java.util.Iterator;
import java.util.LinkedHashSet;
import javax.lang.model.element.ElementKind;
/**
* @author cushon@google.com (Liam Miller-Cushon)
*/
@BugPattern(name = "MissingCasesInEnumSwitch",
summary = "Enum switch statement is missing cases",
explanation = "Enums on switches should either handle all possible values of the enum, or"
+ " have an explicit 'default' case.",
category = JDK, severity = ERROR, maturity = EXPERIMENTAL)
public class MissingCasesInEnumSwitch extends BugChecker
implements SwitchTreeMatcher {
@Override
public Description matchSwitch(SwitchTree tree, VisitorState state) {
TypeSymbol switchType = ((JCSwitch) tree).getExpression().type.tsym;
if (switchType.getKind() != ElementKind.ENUM) {
return Description.NO_MATCH;
}
if (hasDefaultCase(tree)) {
return Description.NO_MATCH;
}
LinkedHashSet<String> unhandled =
setDifference(ASTHelpers.enumValues(switchType), collectEnumSwitchCases(tree));
if (unhandled.isEmpty()) {
return Description.NO_MATCH;
}
return Description.builder(tree, pattern).setMessage(buildMessage(unhandled)).build();
}
/**
* Build the diagnostic message.
*
* <p>Examples:
* <ul>
* <li>Non-exhaustive switch, expected cases for: FOO
* <li>Non-exhaustive switch, expected cases for: FOO, BAR, BAZ, and 42 others. Did you mean to
* include a 'default' case?
* </ul>
*/
private String buildMessage(LinkedHashSet<String> unhandled) {
final int maxCasesToPrint = 5;
StringBuilder message = new StringBuilder("Non-exhaustive switch, expected cases for: ");
boolean tooManyCasesToPrint = unhandled.size() > maxCasesToPrint;
int numberToShow = tooManyCasesToPrint
? 3 // if there are too many to print, only show three examples.
: unhandled.size();
Iterator<String> it = unhandled.iterator();
for (int i = 0; i < numberToShow; ++i) {
if (i != 0) {
message.append(", ");
}
message.append(it.next());
}
if (tooManyCasesToPrint) {
message.append(String.format(", and %d others. Did you mean to include a 'default' case?",
unhandled.size() - numberToShow));
} else {
message.append(".");
}
return message.toString();
}
/** Return the enum values handled by the given switch statement's cases. */
private static LinkedHashSet<String> collectEnumSwitchCases(SwitchTree tree) {
LinkedHashSet<String> cases = new LinkedHashSet<>();
for (CaseTree caseTree : tree.getCases()) {
ExpressionTree pat = caseTree.getExpression();
if (pat instanceof IdentifierTree) {
cases.add(((IdentifierTree) pat).getName().toString());
}
}
return cases;
}
/** Return the difference of sets ax and bx. */
private static <T> LinkedHashSet<T> setDifference(LinkedHashSet<T> ax, LinkedHashSet<T> bx) {
LinkedHashSet<T> result = new LinkedHashSet<>(ax);
result.removeAll(bx);
return result;
}
/** Return true if the switch has a 'default' case. */
private static boolean hasDefaultCase(SwitchTree tree) {
for (CaseTree caseTree : tree.getCases()) {
if (isDefaultCase(caseTree)) {
return true;
}
}
return false;
}
/** The 'default' case is represented in the AST as a CaseTree with a null expression. */
private static boolean isDefaultCase(CaseTree tree) {
return tree.getExpression() == null;
}
}