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SONARJAVA-6874 S9351: Fix FPs on null checks and normalized scales #6057

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Merged
nathsou merged 2 commits into from
Aug 28, 2026
+65 −3
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SONARJAVA-6874 S9351: Fix FPs on null checks and normalized scales #6057

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d29eae7
RC-289 S9351: Fix FPs on normalized BigDecimals
nathsou Aug 28, 2026
6d0061a
RC-289 Handle inherited BigDecimal setScale calls
nathsou Aug 28, 2026
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5 changes: 5 additions & 0 deletions java-checks-test-sources/default/src/main/java/checks/BigDecimalEqualsCheckGuavaSample.java
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,11 @@ void method(BigDecimal a, BigDecimal b, Object o, String s) {

// Compliant
res = com.google.common.base.Objects.equal(s, "hello");
res = com.google.common.base.Objects.equal(null, s);
res = com.google.common.base.Objects.equal(s, null);
res = com.google.common.base.Objects.equal(null, a);
res = com.google.common.base.Objects.equal(a, null);
res = com.google.common.base.Objects.equal(a.setScale(2), b.setScale(2));
}

static class AccountWithGuavaEquals {
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20 changes: 19 additions & 1 deletion java-checks-test-sources/default/src/main/java/checks/BigDecimalEqualsCheckSample.java
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Expand Up @@ -5,7 +5,9 @@

class BigDecimalEqualsCheckSample {

void method(BigDecimal a, BigDecimal b, Object o, String s) {
private static final int SCALE = 2;

void method(BigDecimal a, BigDecimal b, Object o, String s, int runtimeScaleA, int runtimeScaleB) {
boolean res;

res = a.equals(b); // Noncompliant [["BigDecimal.equals()" compares scale as well as value; use "compareTo() == 0" for numerical comparison.]]
Expand All @@ -18,6 +20,11 @@ void method(BigDecimal a, BigDecimal b, Object o, String s) {
// ^^^^^^
res = Objects.equals(a, o); // Noncompliant
res = Objects.equals(o, a); // Noncompliant
res = a.setScale(2).equals(b); // Noncompliant
res = a.equals(b.setScale(2)); // Noncompliant
res = a.setScale(2).equals(b.setScale(3)); // Noncompliant
res = a.setScale(runtimeScaleA).equals(b.setScale(runtimeScaleB)); // Noncompliant
res = Objects.equals(a.setScale(2), b); // Noncompliant

// Compliant
res = a.compareTo(b) == 0;
Expand All @@ -26,6 +33,16 @@ void method(BigDecimal a, BigDecimal b, Object o, String s) {
res = s.equals(a);
res = s.equals("hello");
res = Objects.equals(s, "hello");
res = Objects.equals(null, s);
res = Objects.equals(s, null);
res = Objects.equals(null, a);
res = Objects.equals(a, null);
res = Objects.equals((null), s);
res = a.setScale(2).equals(b.setScale(2));
res = a.setScale(2, java.math.RoundingMode.UP).equals(b.setScale(2, java.math.RoundingMode.DOWN));
res = a.setScale(SCALE, java.math.RoundingMode.HALF_UP).equals(b.setScale(SCALE, java.math.RoundingMode.HALF_UP));
res = (a.setScale(2)).equals((b.setScale(2)));
res = Objects.equals(a.setScale(2), b.setScale(2));
}

static class Account {
Expand Down Expand Up @@ -67,6 +84,7 @@ public MyBigDecimal(String val) {

void testCustom(MyBigDecimal other) {
boolean r = this.equals(other); // Noncompliant
r = this.setScale(2).equals(other.setScale(2));
}
}
}
43 changes: 41 additions & 2 deletions java-checks/src/main/java/org/sonar/java/checks/BigDecimalEqualsCheck.java
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Expand Up @@ -18,13 +18,16 @@

import java.util.Collections;
import java.util.List;
import java.util.Optional;
import org.sonar.check.Rule;
import org.sonar.java.checks.helpers.MethodTreeUtils;
import org.sonar.java.model.ExpressionUtils;
import org.sonar.plugins.java.api.IssuableSubscriptionVisitor;
import org.sonar.plugins.java.api.semantic.MethodMatchers;
import org.sonar.plugins.java.api.semantic.Type;
import org.sonar.plugins.java.api.tree.Arguments;
import org.sonar.plugins.java.api.tree.ExpressionTree;
import org.sonar.plugins.java.api.tree.MemberSelectExpressionTree;
import org.sonar.plugins.java.api.tree.MethodInvocationTree;
import org.sonar.plugins.java.api.tree.MethodTree;
import org.sonar.plugins.java.api.tree.Tree;
Expand All @@ -48,6 +51,14 @@ public class BigDecimalEqualsCheck extends IssuableSubscriptionVisitor {
.addParametersMatcher(JAVA_LANG_OBJECT, JAVA_LANG_OBJECT)
.build();

private static final MethodMatchers SET_SCALE = MethodMatchers.create()
.ofTypes(BIG_DECIMAL)
.names("setScale")
.addParametersMatcher("int")
.addParametersMatcher("int", "int")
.addParametersMatcher("int", "java.math.RoundingMode")
.build();
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@Override
public List<Tree.Kind> nodesToVisit() {
return Collections.singletonList(Tree.Kind.METHOD_INVOCATION);
Expand All @@ -60,17 +71,45 @@ public void visitNode(Tree tree) {
return;
}
if (INSTANCE_EQUALS.matches(mit)) {
reportIssue(ExpressionUtils.methodName(mit), MESSAGE);
if (!hasSameKnownScale(mit)) {
reportIssue(ExpressionUtils.methodName(mit), MESSAGE);
}
} else if (STATIC_EQUALS.matches(mit)) {
Arguments arguments = mit.arguments();
Type firstType = arguments.get(0).symbolType();
Type secondType = arguments.get(1).symbolType();
if (isBigDecimal(firstType) || isBigDecimal(secondType)) {
if (!hasNullArgument(arguments)
&& (isBigDecimal(firstType) || isBigDecimal(secondType))
&& !hasSameKnownScale(arguments.get(0), arguments.get(1))) {
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reportIssue(ExpressionUtils.methodName(mit), MESSAGE);
}
}
}
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private static boolean hasNullArgument(Arguments arguments) {
return arguments.stream().anyMatch(ExpressionUtils::isNullLiteral);
}

private static boolean hasSameKnownScale(MethodInvocationTree invocation) {
if (invocation.methodSelect() instanceof MemberSelectExpressionTree memberSelect) {
return hasSameKnownScale(memberSelect.expression(), invocation.arguments().get(0));
}
return false;
}

private static boolean hasSameKnownScale(ExpressionTree first, ExpressionTree second) {
Optional<Integer> firstScale = setScale(first);
return firstScale.isPresent() && firstScale.equals(setScale(second));
}

private static Optional<Integer> setScale(ExpressionTree expression) {
ExpressionTree unwrapped = ExpressionUtils.skipParentheses(expression);
if (unwrapped instanceof MethodInvocationTree invocation && SET_SCALE.matches(invocation.methodSymbol())) {
return invocation.arguments().get(0).asConstant(Integer.class);
}
return Optional.empty();
}

private static boolean isBigDecimal(Type type) {
return !type.isUnknown() && type.isSubtypeOf(BIG_DECIMAL);
}
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