checker/src/main/java/org/checkerframework/checker/nullness/NullnessChecker.java

package org.checkerframework.checker.nullness;

import java.util.LinkedHashSet;
import java.util.List;
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<Class<? extends BaseTypeChecker>> getImmediateSubcheckerClasses() {
    LinkedHashSet<Class<? extends BaseTypeChecker>> checkers =
        super.getImmediateSubcheckerClasses();
    if (!hasOptionNoSubcheckers("assumeKeyFor")) {
      checkers.add(KeyForSubchecker.class);
    }
    return checkers;
  }

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

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

  @Override
  public List<String> getExtraStubFiles() {
    List<String> result = super.getExtraStubFiles();
    if (hasOption("assumeKeyFor")) {
      result.add("map-assumeKeyFor.astub");
    }
    return result;
  }
}