org.checkerframework.checker.nullness.NullnessChecker Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of checker Show documentation

The Checker Framework enhances Java's type system to make it more powerful and useful. This lets software developers detect and prevent errors in their Java programs. The Checker Framework includes compiler plug-ins ("checkers") that find bugs or verify their absence. It also permits you to write your own compiler plug-ins.

There is a newer version: 3.44.0

Show newest version

package org.checkerframework.checker.nullness;

import java.util.LinkedHashSet;
import java.util.SortedSet;
import javax.annotation.processing.SupportedOptions;
import org.checkerframework.checker.initialization.InitializationChecker;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.checkerframework.common.basetype.BaseTypeChecker;
import org.checkerframework.common.basetype.BaseTypeVisitor;
import org.checkerframework.framework.source.SupportedLintOptions;

/**
 * An implementation of the nullness type-system, parameterized by an initialization type-system for
 * safe initialization. It uses freedom-before-commitment, augmented by type frames (which are
 * crucial to obtain acceptable precision), as its initialization type system.
 *
 * @checker_framework.manual #nullness-checker Nullness Checker
 */
@SupportedLintOptions({
  NullnessChecker.LINT_NOINITFORMONOTONICNONNULL,
  NullnessChecker.LINT_REDUNDANTNULLCOMPARISON,
  // Temporary option to forbid non-null array component types, which is allowed by default.
  // Forbidding is sound and will eventually be the default.
  // Allowing is unsound, as described in Section 3.3.4, "Nullness and arrays":
  //     https://checkerframework.org/manual/#nullness-arrays
  // It is the default temporarily, until we improve the analysis to reduce false positives or we
  // learn what advice to give programmers about avoid false positive warnings.
  // See issue #986: https://github.com/typetools/checker-framework/issues/986
  "soundArrayCreationNullness",
  // Old name for soundArrayCreationNullness, for backward compatibility; remove in January 2021.
  "forbidnonnullarraycomponents",
  NullnessChecker.LINT_TRUSTARRAYLENZERO,
  NullnessChecker.LINT_PERMITCLEARPROPERTY,
})
@SupportedOptions({"assumeKeyFor"})
public class NullnessChecker extends InitializationChecker {

  /** Should we be strict about initialization of {@link MonotonicNonNull} variables? */
  public static final String LINT_NOINITFORMONOTONICNONNULL = "noInitForMonotonicNonNull";

  /** Default for {@link #LINT_NOINITFORMONOTONICNONNULL}. */
  public static final boolean LINT_DEFAULT_NOINITFORMONOTONICNONNULL = false;

  /**
   * Warn about redundant comparisons of an expression with {@code null}, if the expression is known
   * to be non-null.
   */
  public static final String LINT_REDUNDANTNULLCOMPARISON = "redundantNullComparison";

  /** Default for {@link #LINT_REDUNDANTNULLCOMPARISON}. */
  public static final boolean LINT_DEFAULT_REDUNDANTNULLCOMPARISON = false;

  /**
   * Should the Nullness Checker unsoundly trust {@code @ArrayLen(0)} annotations to improve
   * handling of {@link java.util.Collection#toArray()} by {@link CollectionToArrayHeuristics}?
   */
  public static final String LINT_TRUSTARRAYLENZERO = "trustArrayLenZero";

  /** Default for {@link #LINT_TRUSTARRAYLENZERO}. */
  public static final boolean LINT_DEFAULT_TRUSTARRAYLENZERO = false;

  /**
   * If true, client code may clear system properties. If false (the default), some calls to {@code
   * System.getProperty} are refined to return @NonNull.
   */
  public static final String LINT_PERMITCLEARPROPERTY = "permitClearProperty";

  /** Default for {@link #LINT_PERMITCLEARPROPERTY}. */
  public static final boolean LINT_DEFAULT_PERMITCLEARPROPERTY = false;

  @Override
  protected LinkedHashSet> getImmediateSubcheckerClasses() {
    LinkedHashSet> checkers =
        super.getImmediateSubcheckerClasses();
    if (!hasOptionNoSubcheckers("assumeKeyFor")) {
      checkers.add(KeyForSubchecker.class);
    }
    return checkers;
  }

  @Override
  public SortedSet getSuppressWarningsPrefixes() {
    SortedSet result = super.getSuppressWarningsPrefixes();
    result.add("nullness");
    return result;
  }

  @Override
  protected BaseTypeVisitor createSourceVisitor() {
    return new NullnessVisitor(this);
  }
}