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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 2015 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 com.google.common.base.Preconditions.checkState;

import com.google.common.collect.Table;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import org.jspecify.nullness.Nullable;

/** Renames references in code and JSDoc when necessary. */
final class Es6RenameReferences extends AbstractPostOrderCallback {

  private final Table renameTable;
  private final boolean typesOnly;

  Es6RenameReferences(Table renameTable, boolean typesOnly) {
    this.renameTable = renameTable;
    this.typesOnly = typesOnly;
  }

  Es6RenameReferences(Table renameTable) {
    this(renameTable, /* typesOnly= */ false);
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    if (!typesOnly && NodeUtil.isReferenceName(n)) {
      renameNameReference(t, n);
    }

    // Remove this branch after module rewriting is always done
    // after type checking.
    JSDocInfo info = n.getJSDocInfo();
    if (info != null) {
      for (Node root : info.getTypeNodes()) {
        renameTypeNodeRecursive(t, root);
      }
    }
  }

  private void renameTypeNodeRecursive(NodeTraversal t, Node n) {
    if (n.isStringLit()) {
      renameTypeReference(t, n);
    }

    for (Node child = n.getFirstChild(); child != null; child = child.getNext()) {
      renameTypeNodeRecursive(t, child);
    }
  }

  private void renameNameReference(NodeTraversal t, Node n) {
    checkState(n.isName());
    String oldName = n.getString();
    renameReference(t, n, oldName, null, false);
  }

  private void renameTypeReference(NodeTraversal t, Node n) {
    checkState(n.isStringLit());
    String fullName = n.getString();
    String rootName;
    String rest;
    int endPos = fullName.indexOf('.');
    if (endPos == -1) {
      rootName = fullName;
      rest = null;
    } else {
      rootName = fullName.substring(0, endPos);
      rest = fullName.substring(endPos);
    }
    renameReference(t, n, rootName, rest, true);
  }

  /**
   * @param t The NodeTraversal.
   * @param oldName The root name of a qualified name.
   * @param rest The rest of the qualified name or null.
   * @param inJSDoc Whether the rewriting is occuring within JSDoc.
   */
  private void renameReference(
      NodeTraversal t, Node n, String oldName, @Nullable String rest, boolean inJSDoc) {
    Scope current = t.getScope();
    while (current != null) {
      String newName = renameTable.get(current.getRootNode(), oldName);
      if (newName != null) {
        String newFullName = rest == null ? newName : newName + rest;
        n.setString(newFullName);
        // Dont call reportCodeChange for jsdoc changes
        if (!inJSDoc) {
          t.reportCodeChange();
        }
        return;
      } else if (current.hasOwnSlot(oldName)) {
        return;
      } else {
        current = current.getParent();
      }
    }
  }
}