How to use com.oracle.truffle.api.debug

@Override
boolean step(DebuggerSession steppingSession, EventContext context, SuspendAnchor suspendAnchor) {
  boolean hit = current.step(steppingSession, context, suspendAnchor);
  if (hit) {
    if (current == last) {
      return true;
    } else {
      current = current.next;
      current.initialize(SuspendedContext.create(context, steppingSession.getDebugger().getEnv()), suspendAnchor);
    }
  }
  return false;
}

  @Override
  public SuspendedContext get() {
    return SuspendedContext.create(source.getContext(), debugger.getEnv());
  }
});

@Override
protected void onEnter(VirtualFrame frame) {
  if (stepping.get()) {
    doEnter();
    if (hasRootElement) {
      super.onEnter(frame);
    }
  }
}

Debugger(Env env) {
  this.env = env;
  this.msgNodes = new ObjectStructures.MessageNodes();
  this.alwaysHaltBreakpoint = new Breakpoint(BreakpointLocation.ANY, SuspendAnchor.BEFORE, false, null);
  this.alwaysHaltBreakpoint.setEnabled(true);
}

final LanguageInfo resolveLanguage() {
  LanguageInfo languageInfo;
  if (preferredLanguage != null) {
    languageInfo = preferredLanguage;
  } else if (getScope() != null && getScope().getLanguage() != null) {
    languageInfo = getScope().getLanguage();
  } else {
    languageInfo = getOriginalLanguage();
  }
  return languageInfo;
}

/**
 * Returns <code>true</code> if the underlying guest language source location is denoted as the
 * source element.
 *
 * @param sourceElement the source element to check, must not be <code>null</code>.
 * @since 0.33
 */
public boolean hasSourceElement(SourceElement sourceElement) {
  return context.hasTag(sourceElement.getTag());
}

/**
 * Test if the language context of the source of the event is initialized.
 *
 * @since 0.26
 */
public boolean isLanguageContextInitialized() {
  verifyValidState(true);
  return context.isLanguageContextInitialized();
}

@Override
public void onContextClosed(TruffleContext context) {
  DebugContextsListener l = contextsListener;
  if (l != null) {
    DebugContext dc = getCachedDebugContext(context);
    l.contextClosed(dc);
  }
}

@Override
public void onLanguageContextInitialized(TruffleContext context, LanguageInfo language) {
  DebugContextsListener l = contextsListener;
  if (l != null) {
    DebugContext dc = getCachedDebugContext(context);
    l.languageContextInitialized(dc, language);
  }
}

private SuspendedContext getContext() {
  SuspendedContext context = event.getContext();
  if (context == null) {
    // there is a race condition here if the event
    // got disposed between the parent verifyValidState and getContext.
    // if the context is null we assume the event got disposed so we re-check
    // the disposed flag. return null should therefore not be reachable.
    verifyValidState(true);
    assert false : "should not be reachable";
  }
  return context;
}

AbstractBreakpointNode(Breakpoint breakpoint, EventContext context) {
  super(context);
  this.breakpoint = breakpoint;
  initializeSessions();
  this.conditionExistsUnchanged = breakpoint.getConditionExistsUnchanged();
  if (breakpoint.condition != null) {
    this.breakCondition = new ConditionalBreakNode(context, breakpoint);
  }
}

@Override
public void onThreadInitialized(TruffleContext context, Thread thread) {
  DebugThreadsListener l = threadsListener;
  if (l != null) {
    DebugContext dc = getCachedDebugContext(context);
    l.threadInitialized(dc, thread);
  }
}

@Override
public void onLanguageContextFinalized(TruffleContext context, LanguageInfo language) {
  DebugContextsListener l = contextsListener;
  if (l != null) {
    DebugContext dc = getCachedDebugContext(context);
    l.languageContextFinalized(dc, language);
  }
}

@Override
public void onThreadDisposed(TruffleContext context, Thread thread) {
  DebugThreadsListener l = threadsListener;
  if (l != null) {
    DebugContext dc = getCachedDebugContext(context);
    l.threadDisposed(dc, thread);
  }
}

/**
 * Returns the guest language source section of the AST node before/after the execution is
 * suspended. Returns <code>null</code> if no source section information is available.
 * <p>
 * This method is thread-safe.
 *
 * @since 0.17
 */
public SourceSection getSourceSection() {
  verifyValidState(true);
  return session.resolveSection(sourceSection);
}

void resetReportedException() {
  if (haveReportedExceptions.get()) {
    doResetReportedException();
  }
}

Debugger(Env env) {
  this.env = env;
  this.msgNodes = new ObjectStructures.MessageNodes();
  this.alwaysHaltBreakpoint = new Breakpoint(BreakpointLocation.ANY, SuspendAnchor.BEFORE);
  this.alwaysHaltBreakpoint.setEnabled(true);
}

/**
 * Returns <code>true</code> if the underlying guest language source location is denoted as the
 * source element.
 *
 * @param sourceElement the source element to check, must not be <code>null</code>.
 * @since 0.33
 */
public boolean hasSourceElement(SourceElement sourceElement) {
  return context.hasTag(sourceElement.getTag());
}

/**
 * Test if the language context of the source of the event is initialized.
 *
 * @since 0.26
 */
public boolean isLanguageContextInitialized() {
  verifyValidState(true);
  return context.isLanguageContextInitialized();
}

@Override
public void onContextClosed(TruffleContext context) {
  DebugContextsListener l = contextsListener;
  if (l != null) {
    DebugContext dc = getCachedDebugContext(context);
    l.contextClosed(dc);
  }
}