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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.

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/*
 * Copyright 2014 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.collect.ImmutableMap;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.JSDocInfo.Visibility;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.StaticSourceFile;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.ObjectType;
import javax.annotation.Nullable;

/**
 * Helper functions for computing the visibility of names and properties
 * in JavaScript source code.
 *
 * @see CheckAccessControls
 */
public final class AccessControlUtils {

  /** Non-instantiable. */
  private AccessControlUtils() {}

  /**
   * Returns the effective visibility of the given name. This can differ
   * from the name's declared visibility if the file's {@code @fileoverview}
   * JsDoc specifies a default visibility.
   *
   * @param name The name node to compute effective visibility for.
   * @param var The name to compute effective visibility for.
   * @param fileVisibilityMap A map of {@code @fileoverview} visibility
   *     annotations, used to compute the name's default visibility.
   */
  static Visibility getEffectiveNameVisibility(Node name, Var var,
      ImmutableMap fileVisibilityMap) {
    JSDocInfo jsDocInfo = var.getJSDocInfo();
    Visibility raw = (jsDocInfo == null || jsDocInfo.getVisibility() == null)
        ? Visibility.INHERITED
        : jsDocInfo.getVisibility();
    if (raw != Visibility.INHERITED) {
      return raw;
    }
    Visibility defaultVisibilityForFile =
        fileVisibilityMap.get(var.getSourceFile());
    JSType type = name.getJSType();
    boolean createdFromGoogProvide = (type != null && type.isLiteralObject());
    // Ignore @fileoverview visibility when computing the effective visibility
    // for names created by goog.provide.
    //
    // ProcessClosurePrimitives rewrites goog.provide()s as object literal
    // declarations, but the exact form depends on the ordering of the
    // input files. If goog.provide('a.b') occurs in the inputs before
    // goog.provide('a'), it is rewritten like
    //
    // var a={};a.b={};
    //
    // If the file containing goog.provide('a.b') also declares a @fileoverview
    // visibility, it must not apply to a, as this would make every a.* namespace
    // effectively package-private.
    return (createdFromGoogProvide || defaultVisibilityForFile == null)
        ? raw
        : defaultVisibilityForFile;
  }

  /**
   * Returns the effective visibility of the given property. This can differ
   * from the property's declared visibility if the property is inherited from
   * a superclass, or if the file's {@code @fileoverview} JsDoc specifies
   * a default visibility.
   *
   * @param property The property to compute effective visibility for.
   * @param referenceType The JavaScript type of the property.
   * @param fileVisibilityMap A map of {@code @fileoverview} visibility
   *     annotations, used to compute the property's default visibility.
   * @param codingConvention The coding convention in effect (if any),
   *     used to determine whether the property is private by lexical convention
   *     (example: trailing underscore).
   */
  static Visibility getEffectivePropertyVisibility(
      Node property,
      ObjectType referenceType,
      ImmutableMap fileVisibilityMap,
      @Nullable CodingConvention codingConvention) {
    String propertyName = property.getLastChild().getString();
    StaticSourceFile definingSource = getDefiningSource(
        property, referenceType, propertyName);
    Visibility fileOverviewVisibility = fileVisibilityMap.get(definingSource);
    Node parent = property.getParent();
    boolean isOverride = parent.getJSDocInfo() != null
        && parent.isAssign()
        && parent.getFirstChild() == property;
    ObjectType objectType = getObjectType(
        referenceType, isOverride, propertyName);
    if (isOverride) {
      Visibility overridden = getOverriddenPropertyVisibility(
          objectType, propertyName);
      return getEffectiveVisibilityForOverriddenProperty(
          overridden, fileOverviewVisibility, propertyName, codingConvention);
    } else {
      return getEffectiveVisibilityForNonOverriddenProperty(
          property, objectType, fileOverviewVisibility, codingConvention);
    }
  }

  /** Returns the source file in which the given property is defined, or null if it is not known. */
  @Nullable
  static StaticSourceFile getDefiningSource(
      Node node, @Nullable ObjectType referenceType, String propertyName) {
    if (referenceType != null) {
      Node propDefNode = referenceType.getPropertyDefSite(propertyName);
      if (propDefNode != null) {
        return propDefNode.getStaticSourceFile();
      }
    }
    return node.getStaticSourceFile();
  }

  /**
   * Returns the lowest property defined on a class with visibility information.
   */
  @Nullable static ObjectType getObjectType(
      @Nullable ObjectType referenceType,
      boolean isOverride,
      String propertyName) {
    if (referenceType == null) {
      return null;
    }

    // Find the lowest property defined on a class with visibility information.
    ObjectType current = isOverride ? referenceType.getImplicitPrototype() : referenceType;
    for (; current != null; current = current.getImplicitPrototype()) {
      JSDocInfo docInfo = current.getOwnPropertyJSDocInfo(propertyName);
      if (docInfo != null && docInfo.getVisibility() != Visibility.INHERITED) {
        return current;
      }
    }
    return null;
  }

  /** Returns the original visibility of an overridden property. */
  static Visibility getOverriddenPropertyVisibility(ObjectType objectType, String propertyName) {
    return objectType != null
        ? objectType.getOwnPropertyJSDocInfo(propertyName).getVisibility()
        : Visibility.INHERITED;
  }

  /**
   * Returns the effective visibility of the given overridden property. An overridden property
   * inherits the visibility of the property it overrides.
   */
  static Visibility getEffectiveVisibilityForOverriddenProperty(
      Visibility visibility,
      @Nullable Visibility fileOverviewVisibility,
      String propertyName,
      @Nullable CodingConvention codingConvention) {
    if (codingConvention != null && codingConvention.isPrivate(propertyName)) {
      return Visibility.PRIVATE;
    }
    return (fileOverviewVisibility != null
        && visibility == Visibility.INHERITED)
        ? fileOverviewVisibility
        : visibility;
  }

  /**
   * Returns the effective visibility of the given non-overridden property.
   * Non-overridden properties without an explicit visibility annotation
   * receive the default visibility declared in the file's {@code @fileoverview}
   * block, if one exists.
   */
  private static Visibility getEffectiveVisibilityForNonOverriddenProperty(
      Node getprop,
      ObjectType objectType,
      @Nullable Visibility fileOverviewVisibility,
      @Nullable CodingConvention codingConvention) {
    String propertyName = getprop.getLastChild().getString();
    if (codingConvention != null && codingConvention.isPrivate(propertyName)) {
      return Visibility.PRIVATE;
    }
    Visibility raw = Visibility.INHERITED;
    if (objectType != null) {
      raw = objectType.getOwnPropertyJSDocInfo(propertyName).getVisibility();
    }
    JSType type = getprop.getJSType();
    boolean createdFromGoogProvide = (type != null && type.isLiteralObject());
    // Ignore @fileoverview visibility when computing the effective visibility
    // for properties created by goog.provide.
    //
    // ProcessClosurePrimitives rewrites goog.provide()s as object literal
    // declarations, but the exact form depends on the ordering of the
    // input files. If goog.provide('a.b.c') occurs in the inputs before
    // goog.provide('a'), it is rewritten like
    //
    // var a={};a.b={}a.b.c={};
    //
    // If the file containing goog.provide('a.b.c') also declares
    // a @fileoverview visibility, it must not apply to b, as this would make
    // every a.b.* namespace effectively package-private.
    return (raw != Visibility.INHERITED
        || fileOverviewVisibility == null
        || createdFromGoogProvide)
        ? raw
        : fileOverviewVisibility;
  }
}




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