[analysis_server] Fix missing selection in override completions

When completing an override, the `throw UnimplementedError()` code should be selected automatically. I think this regressed recently because it broke Dart-Code's integration tests (but apparently we didn't have a test for it here). This fixes the issue and adds a test.

Fixes https://github.com/Dart-Code/Dart-Code/issues/5652

Change-Id: I9576f2494249c70968566d13fdf95854f0285944
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/448180
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>

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

@@ -324,19 +324,20 @@ lsp.CompletionItem? toLspCompletionItem(
   }
 
   var completion = suggestion.completion;
-  var selectionOffset = (suggestion is KeywordSuggestion)
-      ? suggestion.selectionOffset
-      : completion.length;
-  var selectionLength = 0;
 
-  if (suggestion is SuggestionData) {
-    selectionOffset = (suggestion as SuggestionData).selectionOffset;
-  } else if (suggestion case TypedSuggestion(
-    data: TypeImportData(:var selectionOffset?, :var selectionLength?),
-  )) {
-    selectionOffset = selectionOffset;
-    selectionLength = selectionLength;
-  }
+  var (selectionOffset, selectionLength) = switch (suggestion) {
+    KeywordSuggestion(:var selectionOffset) => (selectionOffset, 0),
+    SuggestionData(:var selectionOffset) => (selectionOffset, 0),
+    TypedSuggestion(
+      data: TypeImportData(:var selectionOffset?, :var selectionLength?),
+    ) =>
+      (selectionOffset, selectionLength),
+    OverrideSuggestion(
+      data: TypeImportData(:var selectionOffset?, :var selectionLength?),
+    ) =>
+      (selectionOffset, selectionLength),
+    _ => (completion.length, 0),
+  };
 
   var insertTextInfo = buildInsertText(
     supportsSnippets: supportsSnippets,

pkg/analysis_server/test/lsp/completion_dart_test.dart

@@ -2420,12 +2420,7 @@ void main() {
 
     var completionLabel = 'MyEnum.value1';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   Future<void> test_importedSymbol_libraryImported_showingEnum() async {
@@ -2454,12 +2449,7 @@ void main() {
 
     var completionLabel = 'MyEnum.value1';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   Future<void> test_insertReplaceRanges() async {
@@ -3267,6 +3257,35 @@ class B extends A {
     expect(labels, contains('override unary-() { … }'));
   }
 
+  Future<void> test_override() async {
+    setCompletionItemSnippetSupport();
+    content = '''
+abstract class Base {
+  String get name;
+}
+
+class Derived extends Base {
+  ^
+}
+''';
+
+    var expectedContent = r'''
+abstract class Base {
+  String get name;
+}
+
+class Derived extends Base {
+  @override
+  // TODO: implement name
+  String get name => ${0:throw UnimplementedError()};
+}
+''';
+
+    var completionLabel = 'override name => …';
+
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
+  }
+
   Future<void> test_plainText() async {
     content = '''
 class MyClass {
@@ -3894,12 +3913,7 @@ void f() {
 
     var completionLabel = 'MyClass';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   Future<void>
@@ -3925,12 +3939,7 @@ void f() {
 ''';
 
     var completionLabel = 'myExtensionMethod()';
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   Future<void>
@@ -4199,12 +4208,7 @@ void f() {
 
     var completionLabel = 'MyClass1';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   Future<void> test_unimportedSymbols_libraryImported_hidingOne() async {
@@ -4229,12 +4233,7 @@ void f() {
 
     var completionLabel = 'MyClass1';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   Future<void> test_unimportedSymbols_libraryImported_showingOther() async {
@@ -4259,12 +4258,7 @@ void f() {
 
     var completionLabel = 'MyClass1';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   // Code completion doesn't include prefixes for auto-imports so when an
@@ -4293,12 +4287,7 @@ void f() {
 
     var completionLabel = 'MyClass1';
 
-    await _checkCompletionEdits(
-      mainFileUri,
-      content,
-      completionLabel,
-      expectedContent,
-    );
+    await _checkCompletionEdits(mainFileUri, completionLabel, expectedContent);
   }
 
   /// This test reproduces a bug where the pathKey hash used in
@@ -4495,7 +4484,6 @@ void f() {
 
     await _checkCompletionEdits(
       importingFileUri,
-      content,
       completionLabel,
       expectedContent,
     );
@@ -4541,7 +4529,6 @@ void f() {
 
     await _checkCompletionEdits(
       importingFileUri,
-      content,
       completionLabel,
       expectedContent,
     );
@@ -4630,9 +4617,11 @@ void f() {
   ///
   /// [content] should contain a `^` at the location where completion should be
   /// invoked/accepted.
+  ///
+  /// [expectedContent] can contain LSP snippet syntax if supported and expected
+  /// in the result.
   Future<void> _checkCompletionEdits(
     Uri fileUri,
-    String content,
     String completionLabel,
     String expectedContent,
   ) async {
@@ -4641,7 +4630,7 @@ void f() {
     await initialAnalysis;
     var res = await getCompletion(fileUri, code.position.position);
 
-    var completion = res.where((c) => c.label == completionLabel).single;
+    var completion = res.singleWhere((c) => c.label == completionLabel);
     var resolvedCompletion = await resolveCompletion(completion);
 
     // Apply both the main completion edit and the additionalTextEdits atomically.
@@ -4649,7 +4638,7 @@ void f() {
       code.code,
       [
         toTextEdit(resolvedCompletion.textEdit!),
-      ].followedBy(resolvedCompletion.additionalTextEdits!).toList(),
+      ].followedBy(resolvedCompletion.additionalTextEdits ?? []).toList(),
     );
 
     expect(newContent, equalsNormalized(expectedContent));