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Update MAIN_METHOD matcher for JDK 25 instance main methods #5701

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Update MAIN_METHOD matcher for JDK 25 instance main methods #5701

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31 changes: 27 additions & 4 deletions check_api/src/main/java/com/google/errorprone/matchers/Matchers.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
import static com.google.common.collect.Iterables.getLast;
import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.common.collect.Streams.stream;
import static com.google.errorprone.matchers.MethodVisibility.Visibility.PRIVATE;
import static com.google.errorprone.matchers.MethodVisibility.Visibility.PUBLIC;
import static com.google.errorprone.predicates.TypePredicates.isDescendantOf;
import static com.google.errorprone.predicates.TypePredicates.isExactType;
Expand Down Expand Up @@ -52,6 +53,7 @@
import com.google.errorprone.suppliers.Supplier;
import com.google.errorprone.suppliers.Suppliers;
import com.google.errorprone.util.ASTHelpers;
import com.google.errorprone.util.SourceVersion;
import com.sun.source.tree.AnnotationTree;
import com.sun.source.tree.AssertTree;
import com.sun.source.tree.AssignmentTree;
Expand Down Expand Up @@ -1454,14 +1456,35 @@ public static <T extends ExpressionTree> Matcher<T> instanceEqualsInvocation() {
return (Matcher<T>) INSTANCE_EQUALS;
}

/**
* Matches main method candidates. On Java 25+, matches as defined in
* <a href="https://docs.oracle.com/javase/specs/jls/se25/html/jls-12.html#jls-12.1.4">JLS 12.1.4</a>:
* named {@code main}, returns {@code void}, not {@code private}, and either has a single {@code
* String[]} parameter or no parameters. On earlier versions, matches the traditional
* {@code public static void main(String[])} signature.
*/
public static final Matcher<MethodTree> MAIN_METHOD =
allOf(
methodHasArity(1),
methodHasVisibility(PUBLIC),
hasModifier(STATIC),
methodReturns(Suppliers.VOID_TYPE),
methodIsNamed("main"),
methodHasParameters(isSameType(Suppliers.arrayOf(STRING_TYPE))));
anyOf(
// Traditional: public static void main(String[])
allOf(
methodHasVisibility(PUBLIC),
hasModifier(STATIC),
methodHasParameters(isSameType(Suppliers.arrayOf(STRING_TYPE)))),
// Java 25+: void main() or void main(String[]), not private
allOf(
supportsInstanceMainMethods(),
not(methodHasVisibility(PRIVATE)),
anyOf(
methodHasNoParameters(),
methodHasParameters(
isSameType(Suppliers.arrayOf(STRING_TYPE)))))));

private static Matcher<MethodTree> supportsInstanceMainMethods() {
return (tree, state) -> SourceVersion.supportsInstanceMainMethods(state.context);
}

private static final Matcher<ExpressionTree> INSTANCE_HASHCODE =
allOf(instanceMethod().anyClass().named("hashCode").withNoParameters(), isSameType(INT_TYPE));
Expand Down
156 changes: 156 additions & 0 deletions core/src/test/java/com/google/errorprone/bugpatterns/SystemExitOutsideMainTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@

package com.google.errorprone.bugpatterns;

import static com.google.common.truth.TruthJUnit.assume;

import com.google.errorprone.CompilationTestHelper;
import org.junit.Test;
import org.junit.runner.RunWith;
Expand Down Expand Up @@ -46,6 +48,7 @@ void f() {

@Test
public void systemExitMainLookalikeWithoutParameters() {
assume().that(Runtime.version().feature()).isLessThan(25);
helper
.addSourceLines(
"Test.java",
Expand All @@ -60,6 +63,22 @@ public static void main() {
.doTest();
}

@Test
public void systemExitMainNoArgsNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
public static void main() {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitMainLookalikeWithTwoParameters() {
helper
Expand All @@ -78,6 +97,7 @@ public static void main(String[] args, int num) {

@Test
public void systemExitMainLookalikeWithoutStatic() {
assume().that(Runtime.version().feature()).isLessThan(25);
helper
.addSourceLines(
"Test.java",
Expand All @@ -92,6 +112,22 @@ public void main(String[] args) {
.doTest();
}

@Test
public void systemExitInstanceMainNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
public void main(String[] args) {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitMainLookalikeDifferentReturnType() {
helper
Expand Down Expand Up @@ -221,4 +257,124 @@ public static void main(String[] args) {
""")
.doTest();
}

@Test
public void systemExitMainLookalikePackagePrivate() {
assume().that(Runtime.version().feature()).isLessThan(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
static void main(String[] args) {
// BUG: Diagnostic contains: SystemExitOutsideMain
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitProtectedMainNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
protected static void main(String[] args) {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitPackagePrivateMainNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
static void main(String[] args) {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitInstanceNoArgsMainNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
void main() {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitInMethodNoArgsMainInClassNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
void main() {
foo();
}

static void foo() {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitInMethodInstanceMainInClassNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
class Test {
void main(String[] args) {
foo();
}

static void foo() {
System.exit(0);
}
}
""")
.doTest();
}

@Test
public void systemExitImplicitlyDeclaredClassNegative() {
assume().that(Runtime.version().feature()).isAtLeast(25);
helper
.addSourceLines(
"Test.java",
"""
void main() {
System.exit(0);
}
""")
.doTest();
}

}