LabeledStatement.java

// Copyright (C) 2005 Google Inc.
//
// 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.caja.parser.js;

import com.google.caja.lexer.FilePosition;
import com.google.caja.lexer.escaping.Escaping;
import com.google.caja.parser.ParseTreeNode;
import com.google.caja.reporting.RenderContext;
import java.util.List;
import java.util.Map;

/**
 * A statement with a label, such as
 * <code>label: for (...) { ... }</code>.
 *
 * <p>Javascript bizarrely allows labels on any statements, but the labels are
 * only useful when applied to loops or switches.</p>
 *
 * <p>The empty string is the default label, so <code>break;</code> breaks with
 * label <code>""</code>.</p>
 *
 * @author mikesamuel@gmail.com
 */
public abstract class LabeledStatement extends AbstractStatement {
  private static final long serialVersionUID = -1825047573111985986L;
  private final String label;

  protected LabeledStatement(
      FilePosition pos,
      String label, Class<? extends ParseTreeNode> childClass) {
    super(pos, childClass);
    assert label != null;
    this.label = label;
  }

  public String getLabel() { return label; }

  /**
   * Is the statement a target for a {@link ContinueStmt continue}?
   * For example, {@code switch} statements can be broken from, but since they
   * are not loops, they cannot be continued to.
   */
  public abstract boolean isTargetForContinue();

  @Override
  public void breaks(Map<String, List<BreakStmt>> labels) {
    super.breaks(labels);
    labels.remove(this.label);
  }

  @Override
  public void continues(Map<String, List<ContinueStmt>> labels) {
    super.continues(labels);
    labels.remove(this.label);
  }

  @Override
  public final Object getValue() { return this.label; }

  /** @return null if no label to render. */
  protected final String getRenderedLabel(RenderContext rc) {
    if (label == null || "".equals(label)) { return null; }
    StringBuilder escapedLabel = new StringBuilder();
    Escaping.escapeJsIdentifier(label, true, escapedLabel);
    return escapedLabel.toString();
  }

}