[Completion] Move the legacy completion handler to using SuggestionCollector.

As discussed, test results have changed to

- include all suggestions containing the prefix instead of starting with the prefix
- suggestion kind is now 'prefix' instead of 'library'


Change-Id: Ica5fe62eaf8d4d0741af112810977f122457759f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/439345
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Keerti Parthasarathy <[email protected]>

Author: keertip

pkg/analysis_server/lib/src/handler/legacy/completion_get_suggestions2.dart

@@ -4,15 +4,15 @@
 
 import 'dart:async';
 
-import 'package:analysis_server/protocol/protocol.dart';
-import 'package:analysis_server/protocol/protocol_generated.dart';
+import 'package:analysis_server/src/handler/legacy/completion_utils.dart';
 import 'package:analysis_server/src/handler/legacy/legacy_handler.dart';
 import 'package:analysis_server/src/legacy_analysis_server.dart';
+import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart';
 import 'package:analysis_server/src/request_handler_mixin.dart';
 import 'package:analysis_server/src/services/completion/completion_performance.dart';
+import 'package:analysis_server/src/services/completion/dart/candidate_suggestion.dart';
 import 'package:analysis_server/src/services/completion/dart/completion_manager.dart';
-import 'package:analysis_server/src/services/completion/dart/fuzzy_filter_sort.dart';
 import 'package:analysis_server/src/services/completion/dart/suggestion_builder.dart';
 import 'package:analysis_server/src/services/completion/yaml/analysis_options_generator.dart';
 import 'package:analysis_server/src/services/completion/yaml/fix_data_generator.dart';
@@ -33,6 +33,36 @@ class CompletionGetSuggestions2Handler extends CompletionHandler
     super.performance,
   );
 
+  /// Computes completion results for [request] and append them to the stream.
+  ///
+  /// Clients should not call this method directly as it is
+  /// automatically called when a client listens to the stream returned by
+  /// 'results'. Subclasses should override this method, append at least one
+  /// result to the controller, and close the controller stream once complete.
+  Future<List<CandidateSuggestion>> computeFinalSuggestions({
+    required CompletionBudget budget,
+    required OperationPerformanceImpl performance,
+    required DartCompletionRequest request,
+    required int maxSuggestions,
+    NotImportedSuggestions? notImportedSuggestions,
+    required bool useFilter,
+    required DartCompletionManager manager,
+  }) async {
+    //
+    // Compute completions generated by server.
+    //
+    return await performance.runAsync('computeSuggestions', (
+      performance,
+    ) async {
+      var collector = await manager.computeFinalizedCandidateSuggestions(
+        request: request,
+        performance: performance,
+        maxSuggestions: maxSuggestions,
+      );
+      return collector.suggestions;
+    });
+  }
+
   /// Computes completion results for [request] and append them to the stream.
   ///
   /// Clients should not call this method directly as it is
@@ -193,9 +223,15 @@ class CompletionGetSuggestions2Handler extends CompletionHandler
       setNewRequest(completionRequest);
 
       var notImportedSuggestions = NotImportedSuggestions();
-      var suggestionBuilders = <CompletionSuggestionBuilder>[];
+      var candidateSuggestions = <CandidateSuggestion>[];
+      var suggestions = <CompletionSuggestion>[];
+      var manager = DartCompletionManager(
+        budget: budget,
+        notImportedSuggestions: notImportedSuggestions,
+      );
       try {
-        suggestionBuilders = await computeSuggestions(
+        candidateSuggestions = await computeFinalSuggestions(
+          manager: manager,
           budget: budget,
           performance: performance,
           request: completionRequest,
@@ -213,27 +249,26 @@ class CompletionGetSuggestions2Handler extends CompletionHandler
           ).toResponse(request.id, clientUriConverter: server.uriConverter),
         );
       }
+      // Keep track of whether the set of results was truncated (because
+      // budget was exhausted).
+      bool isIncomplete =
+          (manager.notImportedSuggestions?.isIncomplete ?? false) ||
+          manager.isTruncated;
 
-      performance.run('filter', (performance) {
-        performance.getDataInt('count').add(suggestionBuilders.length);
-        suggestionBuilders = fuzzyFilterSort(
-          pattern: completionRequest.targetPrefix,
-          suggestions: suggestionBuilders,
-        );
-        performance.getDataInt('matchCount').add(suggestionBuilders.length);
-      });
-
-      var lengthRestricted =
-          suggestionBuilders.take(params.maxResults).toList();
-      completionPerformance.computedSuggestionCount = suggestionBuilders.length;
       completionPerformance.transmittedSuggestionCount =
-          lengthRestricted.length;
-
-      var suggestions = lengthRestricted.map((e) => e.build()).toList();
+          candidateSuggestions.length;
 
-      var isIncomplete =
-          notImportedSuggestions.isIncomplete ||
-          lengthRestricted.length < suggestionBuilders.length;
+      await performance.run('mapSuggestions', (performance) async {
+        for (var candidate in candidateSuggestions) {
+          var item = await candidateToCompletionSuggestion(
+            candidate,
+            completionRequest,
+          );
+          if (item != null) {
+            suggestions.add(item);
+          }
+        }
+      });
 
       performance.run('sendResponse', (_) {
         sendResult(