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Don't report NonFinalStaticField findings for fields modified in @BeforeClass methods #4215

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Dec 14, 2023
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Don't report NonFinalStaticField findings for fields modified in @BeforeClass methods #4215

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121 changes: 79 additions & 42 deletions core/src/main/java/com/google/errorprone/bugpatterns/NonFinalStaticField.java
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Original file line number Diff line number Diff line change
Expand Up @@ -38,15 +38,16 @@
import com.google.errorprone.bugpatterns.BugChecker.VariableTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.CompoundAssignmentTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.tree.UnaryTree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.code.Symbol.VarSymbol;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicBoolean;
import javax.lang.model.element.Modifier;

/** A BugPattern; see the summary. */
Expand All @@ -71,7 +72,11 @@ public Description matchVariable(VariableTree tree, VisitorState state) {
.anyMatch(anno -> hasDirectAnnotationWithSimpleName(tree, anno))) {
return NO_MATCH;
}
if (!canBeRemoved(symbol, state) || isEverMutatedInSameCompilationUnit(symbol, state)) {
IsMutated everMutatedInSameCompilationUnit = isEverMutatedInSameCompilationUnit(symbol, state);
if (everMutatedInSameCompilationUnit == IsMutated.IN_BEFORE_METHOD) {
return NO_MATCH;
}
if (!canBeRemoved(symbol, state) || everMutatedInSameCompilationUnit == IsMutated.TRUE) {
return describeMatch(tree);
}
return describeMatch(
Expand Down Expand Up @@ -117,45 +122,77 @@ private static String getDefaultInitializer(VariableTree tree, VisitorState stat
return "null";
}

private static boolean isEverMutatedInSameCompilationUnit(VarSymbol symbol, VisitorState state) {
AtomicBoolean seen = new AtomicBoolean(false);
new TreeScanner<Void, Void>() {
@Override
public Void visitAssignment(AssignmentTree tree, Void unused) {
if (Objects.equals(getSymbol(tree.getVariable()), symbol)) {
seen.set(true);
}
return super.visitAssignment(tree, null);
}

@Override
public Void visitCompoundAssignment(CompoundAssignmentTree tree, Void unused) {
if (Objects.equals(getSymbol(tree.getVariable()), symbol)) {
seen.set(true);
}
return super.visitCompoundAssignment(tree, null);
}

@Override
public Void visitUnary(UnaryTree tree, Void unused) {
if (Objects.equals(getSymbol(tree.getExpression()), symbol) && isMutating(tree.getKind())) {
seen.set(true);
}
return super.visitUnary(tree, null);
}

private boolean isMutating(Kind kind) {
switch (kind) {
case POSTFIX_DECREMENT:
case POSTFIX_INCREMENT:
case PREFIX_DECREMENT:
case PREFIX_INCREMENT:
return true;
default:
return false;
}
}
}.scan(state.getPath().getCompilationUnit(), null);
return seen.get();
enum IsMutated {
TRUE,
FALSE,
IN_BEFORE_METHOD
}

private static IsMutated isEverMutatedInSameCompilationUnit(
VarSymbol symbol, VisitorState state) {
var scanner =
new TreeScanner<Void, Void>() {
IsMutated isMutated = IsMutated.FALSE;

boolean inBeforeMethod = false;

@Override
public Void visitAssignment(AssignmentTree tree, Void unused) {
if (Objects.equals(getSymbol(tree.getVariable()), symbol)) {
isMutated();
}
return super.visitAssignment(tree, null);
}

@Override
public Void visitCompoundAssignment(CompoundAssignmentTree tree, Void unused) {
if (Objects.equals(getSymbol(tree.getVariable()), symbol)) {
isMutated();
}
return super.visitCompoundAssignment(tree, null);
}

@Override
public Void visitUnary(UnaryTree tree, Void unused) {
if (Objects.equals(getSymbol(tree.getExpression()), symbol)
&& isMutating(tree.getKind())) {
isMutated();
}
return super.visitUnary(tree, null);
}

private void isMutated() {
if (inBeforeMethod) {
isMutated = IsMutated.IN_BEFORE_METHOD;
} else if (isMutated.equals(IsMutated.FALSE)) {
isMutated = IsMutated.TRUE;
}
}

private boolean isMutating(Kind kind) {
switch (kind) {
case POSTFIX_DECREMENT:
case POSTFIX_INCREMENT:
case PREFIX_DECREMENT:
case PREFIX_INCREMENT:
return true;
default:
return false;
}
}

@Override
public Void visitMethod(MethodTree tree, Void unused) {
boolean prev = inBeforeMethod;
try {
inBeforeMethod |= ASTHelpers.hasAnnotation(tree, "org.junit.BeforeClass", state);
return super.visitMethod(tree, null);
} finally {
inBeforeMethod = prev;
}
}
};
scanner.scan(state.getPath().getCompilationUnit(), null);
return scanner.isMutated;
}
}
16 changes: 16 additions & 0 deletions core/src/test/java/com/google/errorprone/bugpatterns/NonFinalStaticFieldTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -211,4 +211,20 @@ public void volatileRemoved() {
"}")
.doTest();
}

@Test
public void beforeClass() {
compilationTestHelper
.addSourceLines(
"Test.java", //
"import org.junit.BeforeClass;",
"public class Test {",
" private static String foo;",
" @BeforeClass",
" public static void setup() {",
" foo = \"\";",
" }",
"}")
.doTest();
}
}
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