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Merged
copybara-service merged 1 commit into from
May 28, 2026
+38 −24
Merged

Internal change #5823

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32 changes: 18 additions & 14 deletions core/src/main/java/com/google/errorprone/bugpatterns/AssertThrowsMinimizer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -69,13 +69,14 @@
import java.util.stream.Stream;
import javax.inject.Inject;
import javax.lang.model.element.ElementKind;
import org.jspecify.annotations.Nullable;

/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(summary = "Minimize the amount of logic in assertThrows", severity = WARNING)
public class AssertThrowsMinimizer extends BugChecker implements MethodTreeMatcher {

private static final Matcher<ExpressionTree> MATCHER =
staticMethod().onClass("org.junit.Assert").named("assertThrows");
anyOf(staticMethod().onClass("org.junit.Assert").named("assertThrows"));

private final ConstantExpressions constantExpressions;
private final boolean useVarType;
Expand Down Expand Up @@ -119,11 +120,10 @@ private Optional<AssertThrows> matchMethodInvocation(
if (!(tree.getArguments().getLast() instanceof LambdaExpressionTree lambdaExpressionTree)) {
return Optional.empty();
}
Type firstArgumentType = getType(tree.getArguments().get(0));
if (firstArgumentType.getTypeArguments().isEmpty()) {
Type exceptionType = getExceptionType(tree, state);
if (exceptionType == null) {
return Optional.empty();
}
Type exceptionType = firstArgumentType.getTypeArguments().get(0);
MethodInvocationTree runnable;
switch (lambdaExpressionTree.getBody()) {
case BlockTree blockTree -> {
Expand Down Expand Up @@ -280,7 +280,7 @@ private boolean needsHoisting(ExpressionTree tree, Type exceptionType, VisitorSt
// constant fields and string concatenation.
return false;
}
if (isCheckedException(exceptionType, state) && !throwsSubtypeOf(tree, exceptionType, state)) {
if (isCheckedExceptionType(exceptionType, state) && !maybeThrows(tree, exceptionType, state)) {
return false;
}
boolean needsHoisting =
Expand Down Expand Up @@ -327,18 +327,22 @@ private boolean newClassTreeNeedsHoisting(NewClassTree tree) {
return !tree.getClassBody().getMembers().stream().allMatch(m -> m instanceof MethodTree);
}

private static boolean throwsSubtypeOf(
ExpressionTree tree, Type exceptionType, VisitorState state) {
Types types = state.getTypes();
return types.isSubtype(state.getSymtab().runtimeExceptionType, exceptionType)
|| getThrownExceptions(tree, state).stream()
.anyMatch(t -> isCheckedException(t, state) && types.isSubtype(t, exceptionType));
private static @Nullable Type getExceptionType(MethodInvocationTree tree, VisitorState state) {
Type firstArgumentType = getType(tree.getArguments().get(0));
if (firstArgumentType.getTypeArguments().isEmpty()) {
return null;
}
return firstArgumentType.getTypeArguments().get(0);
}

private static boolean isCheckedException(Type exception, VisitorState state) {
private static boolean maybeThrows(ExpressionTree tree, Type exceptionType, VisitorState state) {
Types types = state.getTypes();
return !types.isSubtype(exception, state.getSymtab().runtimeExceptionType)
&& !types.isSubtype(exception, state.getSymtab().errorType);
if (types.isSubtype(state.getSymtab().runtimeExceptionType, exceptionType)) {
// The exception is Exception or Throwable, assume anything could throw it
return true;
}
return getThrownExceptions(tree, state).stream()
.anyMatch(t -> types.isAssignable(exceptionType, t));
}

private static final Matcher<ExpressionTree> KNOWN_SAFE =
Expand Down
30 changes: 20 additions & 10 deletions core/src/test/java/com/google/errorprone/bugpatterns/AssertThrowsMinimizerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ interface Builder {
Builder setBar(Bar bar);

Builder setBar(Supplier<Bar> bar);

Foo build();
}
}
Expand Down Expand Up @@ -514,7 +515,7 @@ public static Object getThing() throws Exception {
throw new Exception();
}

public static Object getThingUnchecked() {
public static Object getThingUnchecked() {
throw new RuntimeException();
}

Expand Down Expand Up @@ -679,10 +680,11 @@ public void lambda() {
.addInputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

class Test {
void f() {
Expand All @@ -706,10 +708,11 @@ public void methodReference() {
.addInputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

class Test {
void f() {
Expand All @@ -725,10 +728,11 @@ Bar m() {
.addOutputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

class Test {
void f() {
Expand Down Expand Up @@ -797,10 +801,11 @@ public void anonymousClass() {
.addInputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

class Test {
void f() {
Expand Down Expand Up @@ -867,10 +872,11 @@ abstract class InstanceBarSupplier extends BarSupplier {
.addOutputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

class Test {
void f() {
Expand Down Expand Up @@ -984,10 +990,11 @@ public void varArgs() {
.addInputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

abstract class Test {
void f() {
Expand All @@ -1002,10 +1009,11 @@ void f() {
.addOutputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

abstract class Test {
void f() {
Expand All @@ -1028,10 +1036,11 @@ public void cast() {
.addInputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

abstract class Test {
void f(String s, Object o) {
Expand All @@ -1055,10 +1064,11 @@ void f(String s, Object o) {
.addOutputLines(
"Test.java",
"""
import static org.junit.Assert.assertThrows;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import static org.junit.Assert.assertThrows;

abstract class Test {
void f(String s, Object o) {
Expand Down
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