[Analyzer] Prevent two sets of parens being inserted for setState() when LSP's completeFunctionCalls is enabled

Fixes Dart-Code/Dart-Code#3006.

Change-Id: Idc1ac2b41208a13a887e0c0ece98a255114fc634
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/176242
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/lsp/mapping.dart

@@ -1297,6 +1297,14 @@ Pair<String, lsp.InsertTextFormat> _buildInsertText({
   var insertText = completion;
   var insertTextFormat = lsp.InsertTextFormat.PlainText;
 
+  // SuggestionBuilder already does the equiv of completeFunctionCalls for
+  // some methods (for example Flutter's setState). If the completion already
+  // includes any `(` then disable our own insertion as the special-cased code
+  // will likely provide better code.
+  if (completion.contains('(')) {
+    completeFunctionCalls = false;
+  }
+
   // If the client supports snippets, we can support completeFunctionCalls or
   // setting a selection.
   if (supportsSnippets) {

pkg/analysis_server/test/lsp/completion_dart_test.dart

@@ -31,6 +31,15 @@ class CompletionTest extends AbstractLspAnalysisServerTest {
     );
   }
 
+  @override
+  void setUp() {
+    super.setUp();
+    writePackageConfig(
+      projectFolderPath,
+      flutter: true,
+    );
+  }
+
   Future<void> test_commitCharacter_completionItem() async {
     await provideConfig(
       () => initialize(
@@ -124,6 +133,55 @@ main() {
     );
   }
 
+  Future<void> test_completeFunctionCalls_flutterSetState() async {
+    // Flutter's setState method has special handling inside SuggestionBuilder
+    // that already adds in a selection (which overlaps with completeFunctionCalls).
+    // Ensure we don't end up with two sets of parens/placeholders in this case.
+    final content = '''
+import 'package:flutter/material.dart';
+
+class MyWidget extends StatefulWidget {
+  @override
+  _MyWidgetState createState() => _MyWidgetState();
+}
+
+class _MyWidgetState extends State<MyWidget> {
+  @override
+  Widget build(BuildContext context) {
+    [[setSt^]]
+    return Container();
+  }
+}
+    ''';
+
+    await provideConfig(
+      () => initialize(
+        textDocumentCapabilities: withCompletionItemSnippetSupport(
+            emptyTextDocumentClientCapabilities),
+        workspaceCapabilities:
+            withConfigurationSupport(emptyWorkspaceClientCapabilities),
+      ),
+      {'completeFunctionCalls': true},
+    );
+    await openFile(mainFileUri, withoutMarkers(content));
+    final res = await getCompletion(mainFileUri, positionFromMarker(content));
+    final item = res.singleWhere((c) => c.label.startsWith('setState('));
+
+    // Usually the label would be "setState(…)" but here it's slightly different
+    // to indicate a full statement is being inserted.
+    expect(item.label, equals('setState(() {});'));
+
+    // Ensure the snippet comes through in the expected format with the expected
+    // placeholders.
+    expect(item.insertTextFormat, equals(InsertTextFormat.Snippet));
+    expect(item.insertText, equals('setState(() {\n      \${0:}\n    \\});'));
+    expect(item.textEdit.newText, equals(item.insertText));
+    expect(
+      item.textEdit.range,
+      equals(rangeFromMarkers(content)),
+    );
+  }
+
   Future<void> test_completeFunctionCalls_noRequiredParameters() async {
     final content = '''
     void myFunction({int a}) {}