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

package org.checkerframework.checker.nullness;

import com.sun.source.tree.MethodInvocationTree;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import javax.annotation.processing.ProcessingEnvironment;
import javax.lang.model.element.ExecutableElement;
import org.checkerframework.framework.type.AnnotatedTypeMirror;
import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedExecutableType;
import org.checkerframework.javacutil.TreeUtils;

/**
 * Utility class for handling {@link java.lang.System#getProperty(String)} and related invocations.
 *
 * <p>The result of the method call is is assumed to be non-null if the argument is a literal key
 * that is guaranteed to be present in the system properties (according to the documentation of
 * {@link java.lang.System#getProperty(String)}), as in {@code
 * System.getProperties("line.separator")}.
 */
public class SystemGetPropertyHandler {

  /**
   * If true, client code may clear system properties, and this class (SystemGetPropertyHandler) has
   * no effect.
   */
  private final boolean permitClearProperty;

  /** The processing environment. */
  private final ProcessingEnvironment env;

  /** The factory for constructing and looking up types. */
  private final NullnessAnnotatedTypeFactory factory;

  /** The System.getProperty(String) method. */
  private final ExecutableElement systemGetProperty;

  /** The System.setProperty(String) method. */
  private final ExecutableElement systemSetProperty;

  /**
   * System properties that are defined at startup on every JVM.
   *
   * <p>This list is from the Javadoc of System.getProperties, for Java 11.
   */
  public static final Collection<String> predefinedSystemProperties =
      new HashSet<>(
          Arrays.asList(
              "java.version",
              "java.version.date",
              "java.vendor",
              "java.vendor.url",
              "java.vendor.version",
              "java.home",
              "java.vm.specification.version",
              "java.vm.specification.vendor",
              "java.vm.specification.name",
              "java.vm.version",
              "java.vm.vendor",
              "java.vm.name",
              "java.specification.version",
              "java.specification.vendor",
              "java.specification.name",
              "java.class.version",
              "java.class.path",
              "java.library.path",
              "java.io.tmpdir",
              "java.compiler",
              "os.name",
              "os.arch",
              "os.version",
              "file.separator",
              "path.separator",
              "line.separator",
              "user.name",
              "user.home",
              "user.dir"));

  /**
   * Creates a SystemGetPropertyHandler.
   *
   * @param env the processing environment
   * @param factory the factory for constructing and looking up types
   * @param permitClearProperty if true, client code may clear system properties, and this object
   *     does nothing
   */
  public SystemGetPropertyHandler(
      ProcessingEnvironment env,
      NullnessAnnotatedTypeFactory factory,
      boolean permitClearProperty) {
    this.env = env;
    this.factory = factory;
    this.permitClearProperty = permitClearProperty;

    systemGetProperty = TreeUtils.getMethod("java.lang.System", "getProperty", 1, env);
    systemSetProperty = TreeUtils.getMethod("java.lang.System", "setProperty", 2, env);
  }

  /**
   * Apply rules regarding System.getProperty and related methods.
   *
   * @param tree a method invocation
   * @param method the method being invoked
   */
  public void handle(MethodInvocationTree tree, AnnotatedExecutableType method) {
    if (permitClearProperty) {
      return;
    }
    if (TreeUtils.isMethodInvocation(tree, systemGetProperty, env)
        || TreeUtils.isMethodInvocation(tree, systemSetProperty, env)) {
      String literal = NullnessVisitor.literalFirstArgument(tree);
      if (literal != null && predefinedSystemProperties.contains(literal)) {
        AnnotatedTypeMirror type = method.getReturnType();
        type.replaceAnnotation(factory.NONNULL);
      }
    }
  }
}