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/*
* Copyright 2016 The Error Prone Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.errorprone.bugpatterns.nullness;
import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.findDeclaration;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.fixByAddingNullableAnnotationToType;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.getNullCheck;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.hasDefinitelyNullBranch;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.isAlreadyAnnotatedNullable;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.nullnessChecksShouldBeConservative;
import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.varsProvenNullByParentIf;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static javax.lang.model.element.ElementKind.FIELD;
import com.google.common.collect.ImmutableSet;
import com.google.errorprone.BugPattern;
import com.google.errorprone.ErrorProneFlags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker;
import com.google.errorprone.bugpatterns.BugChecker.AssignmentTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.BinaryTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.VariableTreeMatcher;
import com.google.errorprone.bugpatterns.nullness.NullnessUtils.NullCheck;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.VariableTree;
import com.sun.tools.javac.code.Symbol;
import javax.inject.Inject;
import javax.lang.model.element.Name;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
summary =
"Field is assigned (or compared against) a definitely null value but is not annotated"
+ " @Nullable",
severity = SUGGESTION)
public class FieldMissingNullable extends BugChecker
implements BinaryTreeMatcher, AssignmentTreeMatcher, VariableTreeMatcher {
private final boolean beingConservative;
@Inject
FieldMissingNullable(ErrorProneFlags flags) {
this.beingConservative = nullnessChecksShouldBeConservative(flags);
}
@Override
public Description matchBinary(BinaryTree tree, VisitorState state) {
if (beingConservative) {
/*
* We occasionally see unnecessary null checks for fields. Probably sometime the checks were
* necessary years ago. Other times, they were never necessary but were inserted, e.g., by
* IDEs as part of an autogenerated equals() implementation.
*/
return NO_MATCH;
}
NullCheck nullCheck = getNullCheck(tree);
if (nullCheck == null) {
return NO_MATCH;
}
// TODO(cpovirk): Consider not adding @Nullable in cases like `checkState(foo != null)`.
return matchIfLocallyDeclaredReferenceFieldWithoutNullable(
/*
* We do want the Symbol here: We conclude that a field may be null if there is code that
* compares *any* access of the field (foo, this.foo, other.foo) to null.
*/
nullCheck.varSymbolButUsuallyPreferBareIdentifier(), tree, state);
}
@Override
public Description matchAssignment(AssignmentTree tree, VisitorState state) {
return match(getSymbol(tree.getVariable()), tree.getExpression(), state);
}
@Override
public Description matchVariable(VariableTree tree, VisitorState state) {
return match(getSymbol(tree), tree.getInitializer(), state);
}
private Description match(Symbol assigned, ExpressionTree expression, VisitorState state) {
if (expression == null) {
return NO_MATCH;
}
ImmutableSet varsProvenNullByParentIf =
varsProvenNullByParentIf(
/*
* Start at the AssignmentTree/VariableTree, not its expression. This matches what we do
* for ReturnMissingNullable, where we start at the ReturnTree and not its expression.
*/
state.getPath().getParentPath());
if (!hasDefinitelyNullBranch(
expression,
// TODO(cpovirk): Precompute a set of definitelyNullVars instead of passing an empty set.
ImmutableSet.of(),
varsProvenNullByParentIf,
state)) {
return NO_MATCH;
}
return matchIfLocallyDeclaredReferenceFieldWithoutNullable(assigned, expression, state);
}
private Description matchIfLocallyDeclaredReferenceFieldWithoutNullable(
Symbol assigned, ExpressionTree treeToReportOn, VisitorState state) {
if (assigned == null || assigned.getKind() != FIELD || assigned.type.isPrimitive()) {
return NO_MATCH;
}
/*
* TODO(cpovirk): In conservative mode, consider skipping fields whose type is a type-variable
* usage, just as we do in ReturnMissingNullable. (Alternatively, we may decide that that's
* *too* conservative, even for ReturnMissingNullable.)
*/
if (isAlreadyAnnotatedNullable(assigned)) {
return NO_MATCH;
}
VariableTree fieldDecl = findDeclaration(state, assigned);
if (fieldDecl == null) {
return NO_MATCH;
}
SuggestedFix fix = fixByAddingNullableAnnotationToType(state, fieldDecl);
if (fix.isEmpty()) {
return NO_MATCH;
}
return describeMatch(treeToReportOn, fix);
}
}
