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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2008 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp;

import com.google.common.base.Preconditions;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;

import java.util.LinkedHashMap;
import java.util.LinkedHashSet;

/**
 * Records all of the symbols and properties that should be exported.
 *
 * Currently applies to:
 * - function foo() {}
 * - var foo = function() {}
 * - foo.bar = function() {}
 * - var FOO = ...;
 * - foo.BAR = ...;
 *
 * FOO = BAR = 5;
 * and
 * var FOO = BAR = 5;
 * are not supported because the annotation is ambiguous to whether it applies
 * to all the variables or only the first one.
 *
 */
class FindExportableNodes extends AbstractPostOrderCallback {

  static final DiagnosticType NON_GLOBAL_ERROR =
      DiagnosticType.error("JSC_NON_GLOBAL_ERROR",
          "@export only applies to symbols/properties defined in the "
          + "global scope.");

  static final DiagnosticType EXPORT_ANNOTATION_NOT_ALLOWED =
      DiagnosticType.error("JSC_EXPORT_ANNOTATION_NOT_ALLOWED",
          "@export is not supported on this expression.");

  private final AbstractCompiler compiler;

  /**
   * The set of node with @export annotations and their associated fully qualified names
   */
  private final LinkedHashMap exports = new LinkedHashMap<>();

  /**
   * The set of property names associated with @export annotations that do not have
   * an associated fully qualified name.
   */
  private final LinkedHashSet localExports = new LinkedHashSet<>();

  private final boolean allowLocalExports;

  FindExportableNodes(
      AbstractCompiler compiler, boolean allowLocalExports) {
    this.compiler = compiler;
    this.allowLocalExports = allowLocalExports;
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    JSDocInfo docInfo = n.getJSDocInfo();
    if (docInfo != null && docInfo.isExport()) {

      if (parent.isAssign() && (n.isFunction() || n.isClass())) {
        JSDocInfo parentInfo = parent.getJSDocInfo();
        if (parentInfo != null && parentInfo.isExport()) {
          // ScopedAliases produces export annotations on both the function/class
          // node and assign node, we only want to visit the assign node.
          return;
        }
      }

      Mode mode = null;
      String export = null;
      Node context = null;

      switch (n.getToken()) {
        case FUNCTION:
        case CLASS:
          if (parent.isScript()) {
            export = NodeUtil.getName(n);
            context = n;
            mode = Mode.EXPORT;
          }
          break;

        case MEMBER_FUNCTION_DEF:
          export = n.getString();
          context = n;
          mode = Mode.EXPORT;
          break;

        case ASSIGN:
          Node grandparent = parent.getParent();
          if (parent.isExprResult() && !n.getLastChild().isAssign()) {
            if (grandparent != null
                && grandparent.isScript()
                && n.getFirstChild().isQualifiedName()) {
              export = n.getFirstChild().getQualifiedName();
              context = n;
              mode = Mode.EXPORT;
            } else if (allowLocalExports && n.getFirstChild().isGetProp()) {
              Node target = n.getFirstChild();
              export = target.getLastChild().getString();
              mode = Mode.EXTERN;
            }
          }
          break;

        case VAR:
        case LET:
        case CONST:
          if (parent.isScript()) {
            if (n.getFirstChild().hasChildren() && !n.getFirstFirstChild().isAssign()) {
              export = n.getFirstChild().getString();
              context = n;
              mode = Mode.EXPORT;
            }
          }
          break;

        case GETPROP:
          if (allowLocalExports && parent.isExprResult()) {
            mode = Mode.EXTERN;
            export = n.getLastChild().getString();
            mode = Mode.EXTERN;
          }
          break;

        case STRING_KEY:
        case GETTER_DEF:
        case SETTER_DEF:
          if (allowLocalExports) {
            export = n.getString();
            mode = Mode.EXTERN;
          }
          break;
        default:
          break;
      }

      if (export != null) {
        if (mode == Mode.EXPORT) {
          Preconditions.checkNotNull(context);
          exports.put(export, context);
        } else {
          Preconditions.checkState(context == null);
          Preconditions.checkState(mode == Mode.EXTERN);
          Preconditions.checkState(!export.isEmpty());
          localExports.add(export);
        }
      } else {
        // Don't produce extra warnings for functions values of object literals
        if (!n.isFunction() || !NodeUtil.isObjectLitKey(parent)) {
          if (allowLocalExports) {
            compiler.report(t.makeError(n, EXPORT_ANNOTATION_NOT_ALLOWED));
          } else {
            compiler.report(t.makeError(n, NON_GLOBAL_ERROR));
          }
        }
      }
    }
  }

  LinkedHashMap getExports() {
    return exports;
  }

  LinkedHashSet getLocalExports() {
    return localExports;
  }

  static enum Mode {
    EXPORT,
    EXTERN
  }
}