Create a public API for contributing assists and make assists pluggable

pkg/analysis_server/lib/src/edit/edit_domain.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library edit.domain;
 
 import 'dart:async';
 
+import 'package:analysis_server/edit/assist/assist_core.dart';
 import 'package:analysis_server/edit/fix/fix_core.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/plugin/server_plugin.dart';
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
 import 'package:analysis_server/src/services/correction/assist.dart';
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/correction/sort_members.dart';
 import 'package:analysis_server/src/services/correction/status.dart';
@@ skipping 88 matching lines @@
       SourceEdit edit =
           new SourceEdit(0, unformattedSource.length, formattedSource);
       edits.add(edit);
     }
 
     return new EditFormatResult(edits, formattedResult.selectionStart,
         formattedResult.selectionLength).toResponse(request.id);
   }
 
   Response getAssists(Request request) {
-    var params = new EditGetAssistsParams.fromRequest(request);
+    EditGetAssistsParams params = new EditGetAssistsParams.fromRequest(request);
+    ContextSourcePair pair = server.getContextSourcePair(params.file);
+    engine.AnalysisContext context = pair.context;
+    Source source = pair.source;
     List<SourceChange> changes = <SourceChange>[];
-    List<CompilationUnit> units =
-        server.getResolvedCompilationUnits(params.file);
-    if (units.isNotEmpty) {
-      CompilationUnit unit = units[0];
-      List<Assist> assists = computeAssists(unit, params.offset, params.length);
+    if (context != null && source != null) {
+      List<Assist> assists = computeAssists(plugin, context,
+          source, params.offset, params.length);
       assists.forEach((Assist assist) {
         changes.add(assist.change);
       });
     }
-    // respond
     return new EditGetAssistsResult(changes).toResponse(request.id);
   }
 
   Response getFixes(Request request) {
     var params = new EditGetFixesParams.fromRequest(request);
     String file = params.file;
     int offset = params.offset;
     // add fixes
     List<AnalysisErrorFixes> errorFixesList = <AnalysisErrorFixes>[];
     List<CompilationUnit> units = server.getResolvedCompilationUnits(file);
@@ skipping 493 matching lines @@
     }
     if (refactoring is RenameRefactoring) {
       RenameRefactoring renameRefactoring = refactoring;
       RenameOptions renameOptions = params.options;
       renameRefactoring.newName = renameOptions.newName;
       return renameRefactoring.checkNewName();
     }
     return new RefactoringStatus();
   }
 }