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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 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.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.Node;

import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.Map;


/**
 * Extract a list of all function nodes defined in a JavaScript
 * program, assigns them globally unique ids and computes their fully
 * qualified names.  Function names are derived from the property they
 * are assigned to and the scope they are defined in.  For instance,
 * the following code
 *
 * goog.widget = function(str) {
 *   this.member_fn = function() {}
 *   local_fn = function() {}
 *   goog.array.map(arr, function(){});
 * }
 *
 * defines the following functions
 *
 *  goog.widget
 *  goog.widget.member_fn
 *  goog.widget::local_fn
 *  goog.widget::<anonymous>
 *
 */

class FunctionNames implements CompilerPass, Serializable {
  private static final long serialVersionUID = 1L;

  private final transient AbstractCompiler compiler;
  private final Map functionMap = new LinkedHashMap<>();
  private final transient FunctionListExtractor functionListExtractor;

  FunctionNames(AbstractCompiler compiler) {
    this.compiler = compiler;
    this.functionListExtractor = new FunctionListExtractor(functionMap);
  }

  @Override
  public void process(Node externs, Node root) {
    NodeTraversal.traverseEs6(compiler, root, functionListExtractor);
    FunctionExpressionNamer namer = new FunctionExpressionNamer(functionMap);
    AnonymousFunctionNamingCallback namingCallback =
        new AnonymousFunctionNamingCallback(namer);
    NodeTraversal.traverseEs6(compiler, root, namingCallback);
  }

  public Iterable getFunctionNodeList() {
    return functionMap.keySet();
  }

  public int getFunctionId(Node f) {
    FunctionRecord record = functionMap.get(f);
    if (record != null) {
      return record.id;
    } else {
      return -1;
    }
  }

  public String getFunctionName(Node f) {
    FunctionRecord record = functionMap.get(f);
    if (record == null) {
      // Function node was added during compilation and has no name.
      return null;
    }

    String str = record.name;
    if (str.isEmpty()) {
      str = "";
    }

    Node parent = record.parent;
    if (parent != null) {
      str = getFunctionName(parent) + "::" + str;
    }

    // this.foo -> foo
    str = str.replace("::this.", ".");
    // foo.prototype.bar -> foo.bar
    // AnonymousFunctionNamingCallback already replaces ".prototype."
    // with "..", just remove the extra dot.
    str = str.replace("..", ".");
    // remove toplevel anonymous blocks, if they exists.
    str = str.replaceFirst("^(::)*", "");
    return str;
  }

  private static class FunctionRecord implements Serializable {
    private static final long serialVersionUID = 1L;

    public final int id;
    public final Node parent;
    public String name;

    FunctionRecord(int id, Node parent, String name) {
      this.id = id;
      this.parent = parent;
      this.name = name;
    }
  }

  private static class FunctionListExtractor extends AbstractPostOrderCallback {
    private final Map functionMap;
    private int nextId = 0;

    FunctionListExtractor(Map functionMap) {
      this.functionMap = functionMap;
    }

    @Override
    public void visit(NodeTraversal t, Node n, Node parent) {
      if (n.isFunction()) {
        Node functionNameNode = n.getFirstChild();
        String functionName = functionNameNode.getString();

        Node enclosingFunction = t.getEnclosingFunction();

        functionMap.put(n,
            new FunctionRecord(nextId, enclosingFunction, functionName));
        nextId++;
      }
    }
  }

  private static class FunctionExpressionNamer
      implements AnonymousFunctionNamingCallback.FunctionNamer {
    private static final char DELIMITER = '.';
    private static final NodeNameExtractor extractor =
        new NodeNameExtractor(DELIMITER);
    private final Map functionMap;

    FunctionExpressionNamer(Map functionMap) {
      this.functionMap = functionMap;
    }

    @Override
    public final String getName(Node node) {
      return extractor.getName(node);
    }

    @Override
    public final void setFunctionName(String name, Node fnNode) {
      FunctionRecord record = functionMap.get(fnNode);
      assert(record != null);
      assert(record.name.isEmpty());
      record.name = name;
    }

    @Override
    public final String getCombinedName(String lhs, String rhs) {
      return lhs + DELIMITER + rhs;
    }
  }
}