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Only hoist the last statement into the assertThrows() lambda. #5842

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Merged
copybara-service merged 1 commit into from
Jun 5, 2026
+22 −38
Merged

Only hoist the last statement into the assertThrows() lambda. #5842

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27 changes: 11 additions & 16 deletions core/src/main/java/com/google/errorprone/bugpatterns/AssertThrowsUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@

import static com.google.common.collect.ImmutableList.toImmutableList;
import static com.google.common.collect.Iterables.getLast;
import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.errorprone.fixes.SuggestedFixes.renameVariableUsages;
import static com.google.errorprone.util.ASTHelpers.getStartPosition;
import static java.util.stream.Collectors.joining;
Expand Down Expand Up @@ -112,6 +111,10 @@ public static Optional<Fix> tryFailToAssertThrows(
resources.stream().map(state::getSourceForNode).collect(joining("\n", "try (", ") {\n")));
fixSuffix = "\n}";
}
// Hoist all but the last statement out of the lambda to narrow the exception scope.
for (StatementTree statement : throwingStatements.subList(0, throwingStatements.size() - 1)) {
fixPrefix.append(state.getSourceForNode(statement)).append("\n");
}
if (!catchStatements.isEmpty()) {
String name = catchTree.getParameter().getName().toString();
String newName = namer.avoidShadowing(name);
Expand All @@ -133,30 +136,22 @@ public static Optional<Fix> tryFailToAssertThrows(
.map(t -> state.getSourceForNode(t) + ", ")
.orElse(""),
state.getSourceForNode(catchTree.getParameter().getType())));
boolean useExpressionLambda =
throwingStatements.size() == 1
&& getOnlyElement(throwingStatements) instanceof ExpressionStatementTree;
StatementTree lastStatement = getLast(throwingStatements);
boolean useExpressionLambda = lastStatement instanceof ExpressionStatementTree;
if (!useExpressionLambda) {
fixPrefix.append("{");
}
fix.replace(
getStartPosition(tryTree),
getStartPosition(throwingStatements.iterator().next()),
fixPrefix.toString());
fix.replace(getStartPosition(tryTree), getStartPosition(lastStatement), fixPrefix.toString());
if (useExpressionLambda) {
fix.postfixWith(
((ExpressionStatementTree) throwingStatements.iterator().next()).getExpression(), ")");
fix.postfixWith(((ExpressionStatementTree) lastStatement).getExpression(), ")");
} else {
fix.postfixWith(getLast(throwingStatements), "});");
fix.postfixWith(lastStatement, "});");
}
if (catchStatements.isEmpty()) {
fix.replace(
state.getEndPosition(getLast(throwingStatements)),
state.getEndPosition(tryTree),
fixSuffix);
fix.replace(state.getEndPosition(lastStatement), state.getEndPosition(tryTree), fixSuffix);
} else {
fix.replace(
/* startPos= */ state.getEndPosition(getLast(throwingStatements)),
/* startPos= */ state.getEndPosition(lastStatement),
/* endPos= */ getStartPosition(catchStatements.getFirst()),
"\n");
fix.replace(
Expand Down
9 changes: 2 additions & 7 deletions core/src/test/java/com/google/errorprone/bugpatterns/MissingFailTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -948,13 +948,8 @@ class ExceptionTest {
@Test
public void f() throws Exception {
Path p = Paths.get("NOSUCH");
IOException e =
assertThrows(
IOException.class,
() -> {
Files.readAllBytes(p);
Files.readAllBytes(p);
});
Files.readAllBytes(p);
IOException e = assertThrows(IOException.class, () -> Files.readAllBytes(p));
assertThat(e).hasMessageThat().contains("NOSUCH");
}

Expand Down
24 changes: 9 additions & 15 deletions core/src/test/java/com/google/errorprone/bugpatterns/TryFailRefactoringTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -45,12 +45,12 @@ public void catchBlock() {

class ExceptionTest {
@Test
public void f(String message) throws Exception {
public void f(String msg) throws Exception {
Path p = Paths.get("NOSUCH");
try {
Files.readAllBytes(p);
Files.readAllBytes(p);
fail(message);
fail(msg);
} catch (IOException e) {
assertThat(e).hasMessageThat().contains("NOSUCH");
}
Expand Down Expand Up @@ -81,16 +81,10 @@ public void g() throws Exception {

class ExceptionTest {
@Test
public void f(String message) throws Exception {
public void f(String msg) throws Exception {
Path p = Paths.get("NOSUCH");
IOException e =
assertThrows(
message,
IOException.class,
() -> {
Files.readAllBytes(p);
Files.readAllBytes(p);
});
Files.readAllBytes(p);
IOException e = assertThrows(msg, IOException.class, () -> Files.readAllBytes(p));
assertThat(e).hasMessageThat().contains("NOSUCH");
}

Expand Down Expand Up @@ -169,11 +163,11 @@ public void tryWithResources() {

class ExceptionTest {
@Test
public void f(String message, CharSource cs) throws IOException {
public void f(String msg, CharSource cs) throws IOException {
try (BufferedReader buf = cs.openBufferedStream();
PushbackReader pbr = new PushbackReader(buf)) {
pbr.read();
fail(message);
fail(msg);
} catch (IOException e) {
assertThat(e).hasMessageThat().contains("NOSUCH");
}
Expand All @@ -195,10 +189,10 @@ public void f(String message, CharSource cs) throws IOException {

class ExceptionTest {
@Test
public void f(String message, CharSource cs) throws IOException {
public void f(String msg, CharSource cs) throws IOException {
try (BufferedReader buf = cs.openBufferedStream();
PushbackReader pbr = new PushbackReader(buf)) {
IOException e = assertThrows(message, IOException.class, () -> pbr.read());
IOException e = assertThrows(msg, IOException.class, () -> pbr.read());
assertThat(e).hasMessageThat().contains("NOSUCH");
}
}
Expand Down
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