Issue 23640. Implement 'analysis.getNavigation' request.

pkg/analysis_server/tool/spec/generated/java/AnalysisServer.java

 /*
  * Copyright (c) 2014, the Dart project authors.
  *
  * Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
  *
  * 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
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    * request will be delayed until it has been computed. If the content of the file changes after
    * this request was received but before a response could be sent, then an error of type
    * CONTENT_MODIFIED will be generated.
    *
    * If a navigation region overlaps (but extends either before or after) the given region of the
    * file it will be included in the result. This means that it is theoretically possible to get the
    * same navigation region in response to multiple requests. Clients can avoid this by always
    * choosing a region that starts at the beginning of a line and ends at the end of a (possibly
    * different) line in the file.
    *
+   * If a request is made for a file which does not exist, or which is not currently subject to
+   * analysis (e.g. because it is not associated with any analysis root specified to
+   * analysis.setAnalysisRoots), an error of type GET_NAVIGATION_INVALID_FILE will be generated.
+   *
    * @param file The file in which navigation information is being requested.
    * @param offset The offset of the region for which navigation information is being requested.
    * @param length The length of the region for which navigation information is being requested.
    */
   public void analysis_getNavigation(String file, int offset, int length, GetNavigationConsumer consumer);
 
   /**
    * {@code analysis.reanalyze}
    *
    * Force the re-analysis of everything contained in the specified analysis roots. This will cause
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    * the response to this request has been sent.
    */
   public void server_shutdown();
 
   /**
    * Start the analysis server.
    */
   public void start() throws Exception;
 
 }