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Rejig OptionalNotPresent to be a) a bit simpler (very debatable), b) …
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…reuse ConstantExpressions, c) and remove a bug.

The only existing finding for this check is a false positive: unknown commit, and the new findings are unknown commit

PiperOrigin-RevId: 421579480
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@graememorgan
graememorgan authored and Error Prone Team committed Jan 13, 2022
1 parent 606d386 commit 895c461
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185 changes: 87 additions & 98 deletions core/src/main/java/com/google/errorprone/bugpatterns/OptionalNotPresent.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,139 +15,128 @@
*/
package com.google.errorprone.bugpatterns;

import static com.google.common.collect.Multisets.removeOccurrences;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.anyOf;
import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod;
import static com.google.errorprone.util.ASTHelpers.getReceiver;

import com.google.common.collect.HashMultiset;
import com.google.common.collect.Multiset;
import com.google.errorprone.BugPattern;
import com.google.errorprone.ErrorProneFlags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.CompilationUnitTreeMatcher;
import com.google.errorprone.bugpatterns.threadsafety.ConstantExpressions;
import com.google.errorprone.bugpatterns.threadsafety.ConstantExpressions.ConstantExpression;
import com.google.errorprone.bugpatterns.threadsafety.ConstantExpressions.ConstantExpression.ConstantExpressionKind;
import com.google.errorprone.bugpatterns.threadsafety.ConstantExpressions.PureMethodInvocation;
import com.google.errorprone.bugpatterns.threadsafety.ConstantExpressions.Truthiness;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.BlockTree;
import com.sun.source.tree.CompilationUnitTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.IfTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.tree.UnaryTree;
import com.sun.source.util.TreeScanner;
import java.util.Iterator;
import javax.annotation.Nullable;
import javax.lang.model.element.Name;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import java.util.stream.Stream;

/** @author mariasam@google.com (Maria Sam) */
@BugPattern(
name = "OptionalNotPresent",
summary =
"One should not call optional.get() inside an if statement that checks "
+ "!optional.isPresent",
"This Optional has been confirmed to be empty at this point, so the call to `get` will"
+ " throw.",
severity = WARNING)
public class OptionalNotPresent extends BugChecker implements MethodInvocationTreeMatcher {
public final class OptionalNotPresent extends BugChecker implements CompilationUnitTreeMatcher {
private static final Matcher<ExpressionTree> OPTIONAL_GET =
anyOf(
instanceMethod().onDescendantOf("com.google.common.base.Optional").named("get"),
instanceMethod().onDescendantOf("java.util.Optional").namedAnyOf("get", "orElseThrow"));

private static final Matcher<ExpressionTree> OPTIONAL_PRESENT =
instanceMethod()
.onDescendantOfAny("com.google.common.base.Optional", "java.util.Optional")
.named("isPresent");
private final ConstantExpressions constantExpressions;

private static final Matcher<ExpressionTree> OPTIONAL_EMPTY =
instanceMethod().onDescendantOf("java.util.Optional").named("isEmpty");
public OptionalNotPresent(ErrorProneFlags flags) {
this.constantExpressions = ConstantExpressions.fromFlags(flags);
}

@Override
public Description matchMethodInvocation(
MethodInvocationTree methodInvocationTree, VisitorState visitorState) {
Iterator<Tree> iter = visitorState.getPath().iterator();
Tree upTree;
if (OPTIONAL_PRESENT.matches(methodInvocationTree, visitorState)) {
// using an iterator to make sure that only !optional.isPresent() matches and not
// !(optional.isPresent() || foo == 7)
iter.next();
upTree = iter.next();
if (!(upTree instanceof UnaryTree) || upTree.getKind() != Kind.LOGICAL_COMPLEMENT) {
return NO_MATCH;
}
} else if (OPTIONAL_EMPTY.matches(methodInvocationTree, visitorState)) {
iter = visitorState.getPath().iterator();
upTree = methodInvocationTree;
} else {
return NO_MATCH;
}
IfTree ifTree = null;
ifTree = possibleIf(ifTree, upTree, iter);
if (ifTree == null) {
return NO_MATCH;
}
TreeScannerInside treeScannerInside = new TreeScannerInside();
ExpressionTree optionalVar = ASTHelpers.getReceiver(methodInvocationTree);
if (optionalVar == null) {
return NO_MATCH;
}
treeScannerInside.scan(ifTree.getThenStatement(), optionalVar);
if (treeScannerInside.hasGet && !treeScannerInside.hasAssignment) {
return describeMatch(methodInvocationTree);
}
public Description matchCompilationUnit(CompilationUnitTree tree, VisitorState state) {
new IfScanner(state).scan(state.getPath(), null);

return NO_MATCH;
}

@Nullable
private static IfTree possibleIf(IfTree ifTree, Tree upTree, Iterator<Tree> iter) {
while (iter.hasNext()) {
// if it's in the body of an if statement, and not the condition, then it does not apply,
// so return null
if (upTree instanceof BlockTree) {
return null;
}
if (upTree instanceof BinaryTree) {
// If an "or" is in the if condition, then it does not apply
if (upTree.getKind() == Kind.CONDITIONAL_OR) {
return null;
}
}
// if it finds an if tree, that means at this point it was not in the body of the then/else
// statements, so !optional.isPresent() is most definitely in the if condition
if (upTree instanceof IfTree) {
ifTree = (IfTree) upTree;
break;
}
// If tree is not a BlockTree or an or, it keeps going up
upTree = iter.next();
/** Scans a compilation unit, keeping track of which things are known to be true and false. */
private final class IfScanner extends SuppressibleTreePathScanner<Void, Void> {
private final Multiset<ConstantExpression> truths = HashMultiset.create();
private final Multiset<ConstantExpression> falsehoods = HashMultiset.create();
private final VisitorState state;

private IfScanner(VisitorState state) {
this.state = state;
}
return ifTree;
}

private static class TreeScannerInside extends TreeScanner<Void, ExpressionTree> {
@Override
public Void visitIf(IfTree tree, Void unused) {
Truthiness truthiness =
constantExpressions.truthiness(tree.getCondition(), /* not= */ false, state);

withinScope(truthiness, tree.getThenStatement());

private boolean hasGet = false;
private boolean hasAssignment = false;
withinScope(
constantExpressions.truthiness(tree.getCondition(), /* not= */ true, state),
tree.getElseStatement());
return null;
}

private void withinScope(Truthiness truthiness, Tree tree) {
truths.addAll(truthiness.requiredTrue());
falsehoods.addAll(truthiness.requiredFalse());
scan(tree, null);
removeOccurrences(truths, truthiness.requiredTrue());
removeOccurrences(falsehoods, truthiness.requiredFalse());
}

@Override
public Void visitMethodInvocation(MethodInvocationTree tree, ExpressionTree optionalVar) {
if (tree.getArguments().stream().anyMatch(m -> ASTHelpers.sameVariable(m, optionalVar))) {
hasAssignment = true;
}
ExpressionTree receiver = ASTHelpers.getReceiver(tree);
if (receiver != null && ASTHelpers.sameVariable(receiver, optionalVar)) {
ExpressionTree treeIdent = tree.getMethodSelect();
if (treeIdent instanceof MemberSelectTree) {
Name identifier = ((MemberSelectTree) treeIdent).getIdentifier();
if (identifier.contentEquals("get") || identifier.contentEquals("orElseThrow")) {
hasGet = true;
}
public Void visitMethodInvocation(MethodInvocationTree tree, Void unused) {
if (OPTIONAL_GET.matches(tree, state)) {
var receiver = getReceiver(tree);
if (receiver != null) {
constantExpressions
.constantExpression(receiver, state)
.ifPresent(o -> checkForEmptiness(tree, o));
}
}
return super.visitMethodInvocation(tree, optionalVar);
return super.visitMethodInvocation(tree, null);
}

@Override
public Void visitAssignment(AssignmentTree assignmentTree, ExpressionTree optionalVar) {
if (ASTHelpers.sameVariable(assignmentTree.getVariable(), optionalVar)) {
hasAssignment = true;
private void checkForEmptiness(
MethodInvocationTree tree, ConstantExpression constantExpression) {
if (getMethodInvocations(truths)
.filter(
truth ->
truth.symbol() instanceof MethodSymbol
&& truth.symbol().getSimpleName().contentEquals("isEmpty"))
.flatMap(truth -> truth.receiver().stream())
.anyMatch(constantExpression::equals)
|| getMethodInvocations(falsehoods)
.filter(
truth ->
truth.symbol() instanceof MethodSymbol
&& truth.symbol().getSimpleName().contentEquals("isPresent"))
.flatMap(truth -> truth.receiver().stream())
.anyMatch(constantExpression::equals)) {
state.reportMatch(describeMatch(tree));
}
return super.visitAssignment(assignmentTree, optionalVar);
}

private Stream<PureMethodInvocation> getMethodInvocations(Multiset<ConstantExpression> truths) {
return truths.stream()
.filter(truth -> truth.kind().equals(ConstantExpressionKind.PURE_METHOD))
.map(ConstantExpression::pureMethod);
}
}
}

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