[analyzer] Don't show duplicate code completions for items imported via multiple libraries

Fixes https://github.com/Dart-Code/Dart-Code/issues/3227.

Change-Id: Iac5704fea4f00470040b6b94bbf508dd916ed234
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/196923
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/lsp/handlers/handler_completion.dart

@@ -357,11 +357,15 @@ class CompletionHandler
               final key = _createImportedSymbolKey(nameKey, declaringUri);
               final importingUris = alreadyImportedSymbols[key];
 
-              // Keep it only if there are either:
-              // - no URIs importing it
-              // - the URIs importing it include this one
+              // Keep it only if:
+              // - no existing imports include it
+              //     (in which case all libraries will be offered as
+              //     auto-imports)
+              // - this is the first imported URI that includes it
+              //     (we don't want to repeat it for each imported library that
+              //     includes it)
               return importingUris == null ||
-                  importingUris.contains('${library.uri}');
+                  importingUris.first == '${library.uri}';
             }).map((item) => declarationToCompletionItem(
                       capabilities,
                       unit.path!,

pkg/analysis_server/test/lsp/completion_dart_test.dart

@@ -1192,6 +1192,95 @@ main() {
     '''));
   }
 
+  Future<void>
+      test_suggestionSets_doesNotDuplicate_importedViaMultipleLibraries() async {
+    // An item that's already imported through multiple libraries that
+    // export it should not result in multiple entries.
+    newFile(
+      join(projectFolderPath, 'lib/source_file.dart'),
+      content: '''
+      class MyExportedClass {}
+      ''',
+    );
+    newFile(
+      join(projectFolderPath, 'lib/reexport1.dart'),
+      content: '''
+      export 'source_file.dart';
+      ''',
+    );
+    newFile(
+      join(projectFolderPath, 'lib/reexport2.dart'),
+      content: '''
+      export 'source_file.dart';
+      ''',
+    );
+
+    final content = '''
+import 'reexport1.dart';
+import 'reexport2.dart';
+
+main() {
+  MyExported^
+}
+    ''';
+
+    final initialAnalysis = waitForAnalysisComplete();
+    await initialize(
+        workspaceCapabilities:
+            withApplyEditSupport(emptyWorkspaceClientCapabilities));
+    await openFile(mainFileUri, withoutMarkers(content));
+    await initialAnalysis;
+
+    final res = await getCompletion(mainFileUri, positionFromMarker(content));
+
+    final completions = res.where((c) => c.label == 'MyExportedClass').toList();
+    expect(completions, hasLength(1));
+  }
+
+  Future<void>
+      test_suggestionSets_doesNotDuplicate_importedViaSingleLibrary() async {
+    // An item that's already imported through a library that exports it
+    // should not result in multiple entries.
+    newFile(
+      join(projectFolderPath, 'lib/source_file.dart'),
+      content: '''
+      class MyExportedClass {}
+      ''',
+    );
+    newFile(
+      join(projectFolderPath, 'lib/reexport1.dart'),
+      content: '''
+      export 'source_file.dart';
+      ''',
+    );
+    newFile(
+      join(projectFolderPath, 'lib/reexport2.dart'),
+      content: '''
+      export 'source_file.dart';
+      ''',
+    );
+
+    final content = '''
+import 'reexport1.dart';
+
+main() {
+  MyExported^
+}
+    ''';
+
+    final initialAnalysis = waitForAnalysisComplete();
+    await initialize(
+        workspaceCapabilities:
+            withApplyEditSupport(emptyWorkspaceClientCapabilities));
+    await openFile(mainFileUri, withoutMarkers(content));
+    await initialAnalysis;
+
+    final res = await getCompletion(mainFileUri, positionFromMarker(content));
+
+    final completions = res.where((c) => c.label == 'MyExportedClass').toList();
+    expect(completions, hasLength(1));
+  }
+
   Future<void> test_suggestionSets_doesNotFilterSymbolsWithSameName() async {
     // Classes here are not re-exports, so should not be filtered out.
     newFile(