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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 2016 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 static java.lang.Math.min;

import com.google.auto.value.AutoValue;
import com.google.errorprone.annotations.Immutable;
import com.google.javascript.jscomp.deps.ModuleNames;
import java.io.Serializable;

/**
 * Basic information on an entry point module.
 *
 * Closure entry points are namespace names, while ES and CommonJS entry points are file paths
 * which are normalized to a namespace name.
 *
 * This class allows error messages to be based on the user-provided name rather than the
 * normalized name.
 */
@AutoValue
@Immutable
public abstract class ModuleIdentifier implements Serializable {
  /** Returns the user-provided name. */
  public abstract String getName();

  /** Returns the Closure namespace name. */
  public abstract String getClosureNamespace();

  /** Returns the module name. */
  public abstract String getModuleName();

  @Override
  public final String toString() {
    if (getClosureNamespace().equals(getModuleName())) {
      return getClosureNamespace();
    }
    return getModuleName() + ":" + getClosureNamespace();
  }

  /**
   * Returns an identifier for a Closure namespace.
   *
   * @param name The Closure namespace. It may be in one of the formats `name.space`,
   *     `goog:name.space` or `goog:moduleName:name.space`, where the latter specifies that the
   *     module and namespace names are different.
   */
  public static ModuleIdentifier forClosure(String name) {
    String normalizedName = name;
    if (normalizedName.startsWith("goog:")) {
      normalizedName = normalizedName.substring("goog:".length());
    }

    String namespace = normalizedName;
    String moduleName = normalizedName;
    int splitPoint = normalizedName.indexOf(':');
    if (splitPoint != -1) {
      moduleName = normalizedName.substring(0, splitPoint);
      namespace = normalizedName.substring(min(splitPoint + 1, normalizedName.length() - 1));
    }

    return new AutoValue_ModuleIdentifier(normalizedName, namespace, moduleName);
  }

  /**
   * Returns an identifier for an ES or CommonJS module.
   *
   * @param filepath Path to the ES or CommonJS module.
   */
  public static ModuleIdentifier forFile(String filepath) {
    String normalizedName = ModuleNames.fileToModuleName(filepath);
    return new AutoValue_ModuleIdentifier(filepath, normalizedName, normalizedName);
  }

  /**
   * Returns an identifier for an --entry_point flag value.
   *
   * @param flagValue The flag value. If it is in one of the formats `goog:name.space` or
   *     `goog:moduleName:name.space`, it is interpreted as a Closure namespace. Otherwise, it is
   *     interpreted as the path to an ES or CommonJS module.
   */
  public static ModuleIdentifier forFlagValue(String flagValue) {
    if (flagValue.startsWith("goog:")) {
      return ModuleIdentifier.forClosure(flagValue);
    } else {
      return ModuleIdentifier.forFile(flagValue);
    }
  }
}