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/*
* Copyright 2018 The Error Prone 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.errorprone.bugpatterns.time;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Matchers.instanceMethod;
import com.google.common.base.Enums;
import com.google.common.base.Optional;
import com.google.common.primitives.Longs;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.Tree;
import java.util.concurrent.TimeUnit;
/** Check for problematic or suspicious TimeUnit conversion calls. */
@BugPattern(
name = "TimeUnitConversionChecker",
summary =
"This TimeUnit conversion looks buggy: converting from a smaller unit to a larger unit "
+ "(and passing a constant), converting to/from the same TimeUnit, or converting "
+ "TimeUnits where the result is statically known to be 0 or 1 are all buggy patterns.",
explanation =
"This checker flags potential problems with TimeUnit conversions: "
+ "1) conversions that are statically known to be equal to 0 or 1; "
+ "2) conversions that are converting from a given unit back to the same unit; "
+ "3) conversions that are converting from a smaller unit to a larger unit and passing "
+ "a constant value",
severity = WARNING)
public final class TimeUnitConversionChecker extends BugChecker
implements MethodInvocationTreeMatcher {
// TODO(kak): We should probably also extend this to recognize TimeUnit.convertTo() invocations
private static final Matcher MATCHER =
instanceMethod()
.onExactClass("java.util.concurrent.TimeUnit")
.namedAnyOf(
"toDays", "toHours", "toMinutes", "toSeconds", "toMillis", "toMicros", "toNanos");
@Override
public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
if (!MATCHER.matches(tree, state)) {
return Description.NO_MATCH;
}
Tree receiverOfConversion = ASTHelpers.getReceiver(tree);
if (receiverOfConversion == null) {
// Usage inside TimeUnit itself, no changes we can make here.
return Description.NO_MATCH;
}
// This trips up on code like:
// TimeUnit SECONDS = TimeUnit.MINUTES;
// long about2500 = SECONDS.toSeconds(42);
// but... I think that's bad enough to ignore here :)
String timeUnitName = ASTHelpers.getSymbol(receiverOfConversion).getSimpleName().toString();
Optional receiver = Enums.getIfPresent(TimeUnit.class, timeUnitName);
if (!receiver.isPresent()) {
return Description.NO_MATCH;
}
String methodName = ASTHelpers.getSymbol(tree).getSimpleName().toString();
TimeUnit convertTo = methodNameToTimeUnit(methodName);
ExpressionTree arg0 = tree.getArguments().get(0);
// if we have a constant and can Long-parse it...
Long constant = Longs.tryParse(String.valueOf(state.getSourceForNode(arg0)));
if (constant != null) {
long converted = invokeConversion(receiver.get(), methodName, constant);
// ... and the conversion results in 0 or 1, just inline it!
if (converted == 0 || converted == 1 || constant == converted) {
SuggestedFix fix = replaceTreeWith(tree, convertTo, converted + "L");
return describeMatch(tree, fix);
}
// otherwise we have a suspect case: SMALLER_UNIT.toLargerUnit(constantValue)
// because: "people usually don't like to have constants like 60_000_000 and use"
// "libraries to turn them into smaller numbers"
if (receiver.get().compareTo(convertTo) < 0) {
// We can't suggest a replacement here, so we just have to error out.
return describeMatch(tree);
}
}
// if we're trying to convert the unit to itself, just return the arg
if (receiver.get().equals(convertTo)) {
SuggestedFix fix = replaceTreeWith(tree, convertTo, state.getSourceForNode(arg0));
return describeMatch(tree, fix);
}
return Description.NO_MATCH;
}
private static SuggestedFix replaceTreeWith(
MethodInvocationTree tree, TimeUnit units, String replacement) {
return SuggestedFix.builder()
.postfixWith(tree, " /* " + units.toString().toLowerCase() + " */")
.replace(tree, replacement)
.build();
}
private static long invokeConversion(TimeUnit timeUnit, String methodName, long duration) {
switch (methodName) {
case "toDays":
return timeUnit.toDays(duration);
case "toHours":
return timeUnit.toHours(duration);
case "toMinutes":
return timeUnit.toMinutes(duration);
case "toSeconds":
return timeUnit.toSeconds(duration);
case "toMillis":
return timeUnit.toMillis(duration);
case "toMicros":
return timeUnit.toMicros(duration);
case "toNanos":
return timeUnit.toNanos(duration);
default:
throw new IllegalArgumentException();
}
}
private static TimeUnit methodNameToTimeUnit(String methodName) {
switch (methodName) {
case "toDays":
return TimeUnit.DAYS;
case "toHours":
return TimeUnit.HOURS;
case "toMinutes":
return TimeUnit.MINUTES;
case "toSeconds":
return TimeUnit.SECONDS;
case "toMillis":
return TimeUnit.MILLISECONDS;
case "toMicros":
return TimeUnit.MICROSECONDS;
case "toNanos":
return TimeUnit.NANOSECONDS;
default:
throw new IllegalArgumentException();
}
}
}
