add completion after export - fixes #24400

pkg/analysis_server/lib/src/services/completion/uri_contributor.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 services.completion.contributor.dart.importuri;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
@@ skipping 30 matching lines @@
   final DartCompletionRequest request;
 
   _UriSuggestionBuilder(this.request);
 
   bool computeFast(AstNode node) {
     node.accept(this);
     return true;
   }
 
   @override
+  visitExportDirective(exportDirective node) {
+    visitNamespaceDirective(node);
+  }
+
+  @override
   visitImportDirective(ImportDirective node) {
+    visitNamespaceDirective(node);
+  }
+
+  visitNamespaceDirective(NamespaceDirective node) {
     StringLiteral uri = node.uri;
     if (uri is SimpleStringLiteral) {
       int offset = request.offset;
       if (uri.offset < offset &&
           (offset < uri.end || offset == uri.offset + 1)) {
-        // Handle degenerate case where import is only line in file
+        // Handle degenerate case where import or export is only line in file
         // and there is no semicolon
         visitSimpleStringLiteral(uri);
       }
     }
   }
 
   @override
   visitSimpleStringLiteral(SimpleStringLiteral node) {
     AstNode parent = node.parent;
-    if (parent is ImportDirective && parent.uri == node) {
+    if (parent is NamespaceDirective && parent.uri == node) {
       String partial = node.literal.lexeme.substring(
           node.contentsOffset - node.offset, request.offset - node.offset);
       request.replacementOffset = node.contentsOffset;
       request.replacementLength = node.contentsEnd - node.contentsOffset;
       _addDartSuggestions();
       _addPackageSuggestions(partial);
       _addFileSuggestions(partial);
     } else if (parent is PartDirective && parent.uri == node) {
       String partial = node.literal.lexeme.substring(
           node.contentsOffset - node.offset, request.offset - node.offset);
@@ skipping 97 matching lines @@
     request.addSuggestion(new CompletionSuggestion(
         CompletionSuggestionKind.IMPORT,
         relevance,
         completion,
         completion.length,
         0,
         false,
         false));
   }
 }