com.google.errorprone.bugpatterns.BigDecimalLiteralDouble Maven / Gradle / Ivy
/*
* Copyright 2016 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;
import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.NewClassTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.matchers.Matchers;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.NewClassTree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.tree.UnaryTree;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Optional;
/**
* Matches usages of {@code new BigDecimal(double)} which lose precision.
*
* @author [email protected] (Eric Dobson)
*/
@BugPattern(summary = "new BigDecimal(double) loses precision in this case.", severity = WARNING)
public class BigDecimalLiteralDouble extends BugChecker implements NewClassTreeMatcher {
private static final BigInteger LONG_MAX = BigInteger.valueOf(Long.MAX_VALUE);
private static final BigInteger LONG_MIN = BigInteger.valueOf(Long.MIN_VALUE);
private static final String BIG_DECIMAL = BigDecimal.class.getName();
private static final Matcher BIGDECIMAL_DOUBLE_CONSTRUCTOR =
Matchers.constructor().forClass(BIG_DECIMAL).withParameters("double");
// Matches literals and unary +/- followed by a literal, since most people conceptually think of
// -1.0 as a literal. Doesn't handle nested unary operators as new BigDecimal(String) doesn't
// accept multiple unary prefixes.
private static boolean floatingPointArgument(ExpressionTree tree) {
if (tree.getKind() == Kind.UNARY_PLUS || tree.getKind() == Kind.UNARY_MINUS) {
tree = ((UnaryTree) tree).getExpression();
}
return tree.getKind() == Kind.DOUBLE_LITERAL || tree.getKind() == Kind.FLOAT_LITERAL;
}
@Override
public Description matchNewClass(NewClassTree tree, VisitorState state) {
if (!BIGDECIMAL_DOUBLE_CONSTRUCTOR.matches(tree, state)) {
return Description.NO_MATCH;
}
ExpressionTree arg = getOnlyElement(tree.getArguments());
if (!floatingPointArgument(arg)) {
return Description.NO_MATCH;
}
return createDescription(arg, state);
}
private Description createDescription(ExpressionTree arg, VisitorState state) {
Number literalNumber = ASTHelpers.constValue(arg, Number.class);
if (literalNumber == null) {
return Description.NO_MATCH;
}
double literal = literalNumber.doubleValue();
// Strip off 'd', 'f' suffixes and _ separators from the source.
String literalString = state.getSourceForNode(arg).replaceAll("[_dDfF]", "");
// We assume that the expected value of `new BigDecimal(double)` is precisely the BigDecimal
// which stringifies to the same String as `double`'s literal.
BigDecimal intendedValue;
try {
intendedValue = new BigDecimal(literalString);
} catch (ArithmeticException e) {
return Description.NO_MATCH;
}
// Compute the actual BigDecimal produced by the expression, and bail if they're equivalent.
BigDecimal actualValue = new BigDecimal(literal);
if (actualValue.compareTo(intendedValue) == 0) {
return Description.NO_MATCH;
}
Optional integralValue = asBigInteger(intendedValue);
if (integralValue.map(BigDecimalLiteralDouble::isWithinLongRange).orElse(false)) {
long longValue = integralValue.get().longValue();
return suggestReplacement(arg, actualValue, String.format("%sL", longValue));
}
return suggestReplacement(arg, actualValue, String.format("\"%s\"", literalString));
}
private Description suggestReplacement(
ExpressionTree tree, BigDecimal actualValue, String replacement) {
return buildDescription(tree)
.setMessage(
message()
+ String.format(" The exact value here is `new BigDecimal(\"%s\")`.", actualValue))
.addFix(SuggestedFix.replace(tree, replacement))
.build();
}
private static Optional asBigInteger(BigDecimal v) {
try {
return Optional.of(v.toBigIntegerExact());
} catch (ArithmeticException e) {
return Optional.empty();
}
}
private static boolean isWithinLongRange(BigInteger v) {
return LONG_MIN.compareTo(v) <= 0 && v.compareTo(LONG_MAX) <= 0;
}
}