[Analyzer] Add support for LSP experimental SnippetTextEdit

Change-Id: Id37a1954c71fb10c4968c5af6a873ad0ef864a5a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/191403
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/lsp_protocol/protocol_custom_generated.dart

@@ -1573,3 +1573,135 @@ class PublishOutlineParams implements ToJsonable {
   @override
   String toString() => jsonEncoder.convert(toJson());
 }
+
+class SnippetTextEdit implements TextEdit, ToJsonable {
+  static const jsonHandler =
+      LspJsonHandler(SnippetTextEdit.canParse, SnippetTextEdit.fromJson);
+
+  SnippetTextEdit(
+      {@required this.insertTextFormat,
+      @required this.range,
+      @required this.newText}) {
+    if (insertTextFormat == null) {
+      throw 'insertTextFormat is required but was not provided';
+    }
+    if (range == null) {
+      throw 'range is required but was not provided';
+    }
+    if (newText == null) {
+      throw 'newText is required but was not provided';
+    }
+  }
+  static SnippetTextEdit fromJson(Map<String, dynamic> json) {
+    final insertTextFormat = json['insertTextFormat'] != null
+        ? InsertTextFormat.fromJson(json['insertTextFormat'])
+        : null;
+    final range = json['range'] != null ? Range.fromJson(json['range']) : null;
+    final newText = json['newText'];
+    return SnippetTextEdit(
+        insertTextFormat: insertTextFormat, range: range, newText: newText);
+  }
+
+  final InsertTextFormat insertTextFormat;
+
+  /// The string to be inserted. For delete operations use an empty string.
+  final String newText;
+
+  /// The range of the text document to be manipulated. To insert text into a
+  /// document create a range where start === end.
+  final Range range;
+
+  Map<String, dynamic> toJson() {
+    var __result = <String, dynamic>{};
+    __result['insertTextFormat'] = insertTextFormat?.toJson() ??
+        (throw 'insertTextFormat is required but was not set');
+    __result['range'] =
+        range?.toJson() ?? (throw 'range is required but was not set');
+    __result['newText'] =
+        newText ?? (throw 'newText is required but was not set');
+    return __result;
+  }
+
+  static bool canParse(Object obj, LspJsonReporter reporter) {
+    if (obj is Map<String, dynamic>) {
+      reporter.push('insertTextFormat');
+      try {
+        if (!obj.containsKey('insertTextFormat')) {
+          reporter.reportError('must not be undefined');
+          return false;
+        }
+        if (obj['insertTextFormat'] == null) {
+          reporter.reportError('must not be null');
+          return false;
+        }
+        if (!(InsertTextFormat.canParse(obj['insertTextFormat'], reporter))) {
+          reporter.reportError('must be of type InsertTextFormat');
+          return false;
+        }
+      } finally {
+        reporter.pop();
+      }
+      reporter.push('range');
+      try {
+        if (!obj.containsKey('range')) {
+          reporter.reportError('must not be undefined');
+          return false;
+        }
+        if (obj['range'] == null) {
+          reporter.reportError('must not be null');
+          return false;
+        }
+        if (!(Range.canParse(obj['range'], reporter))) {
+          reporter.reportError('must be of type Range');
+          return false;
+        }
+      } finally {
+        reporter.pop();
+      }
+      reporter.push('newText');
+      try {
+        if (!obj.containsKey('newText')) {
+          reporter.reportError('must not be undefined');
+          return false;
+        }
+        if (obj['newText'] == null) {
+          reporter.reportError('must not be null');
+          return false;
+        }
+        if (!(obj['newText'] is String)) {
+          reporter.reportError('must be of type String');
+          return false;
+        }
+      } finally {
+        reporter.pop();
+      }
+      return true;
+    } else {
+      reporter.reportError('must be of type SnippetTextEdit');
+      return false;
+    }
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is SnippetTextEdit && other.runtimeType == SnippetTextEdit) {
+      return insertTextFormat == other.insertTextFormat &&
+          range == other.range &&
+          newText == other.newText &&
+          true;
+    }
+    return false;
+  }
+
+  @override
+  int get hashCode {
+    var hash = 0;
+    hash = JenkinsSmiHash.combine(hash, insertTextFormat.hashCode);
+    hash = JenkinsSmiHash.combine(hash, range.hashCode);
+    hash = JenkinsSmiHash.combine(hash, newText.hashCode);
+    return JenkinsSmiHash.finish(hash);
+  }
+
+  @override
+  String toString() => jsonEncoder.convert(toJson());
+}

pkg/analysis_server/lib/lsp_protocol/protocol_generated.dart

@@ -30666,14 +30666,17 @@ class TextDocumentEdit implements ToJsonable {
         ? OptionalVersionedTextDocumentIdentifier.fromJson(json['textDocument'])
         : null;
     final edits = json['edits']
-        ?.map((item) => TextEdit.canParse(item, nullLspJsonReporter)
-            ? Either2<TextEdit, AnnotatedTextEdit>.t1(
-                item != null ? TextEdit.fromJson(item) : null)
+        ?.map((item) => SnippetTextEdit.canParse(item, nullLspJsonReporter)
+            ? Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t1(
+                item != null ? SnippetTextEdit.fromJson(item) : null)
             : (AnnotatedTextEdit.canParse(item, nullLspJsonReporter)
-                ? Either2<TextEdit, AnnotatedTextEdit>.t2(
+                ? Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t2(
                     item != null ? AnnotatedTextEdit.fromJson(item) : null)
-                : (throw '''${item} was not one of (TextEdit, AnnotatedTextEdit)''')))
-        ?.cast<Either2<TextEdit, AnnotatedTextEdit>>()
+                : (TextEdit.canParse(item, nullLspJsonReporter)
+                    ? Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t3(
+                        item != null ? TextEdit.fromJson(item) : null)
+                    : (throw '''${item} was not one of (SnippetTextEdit, AnnotatedTextEdit, TextEdit)'''))))
+        ?.cast<Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>>()
         ?.toList();
     return TextDocumentEdit(textDocument: textDocument, edits: edits);
   }
@@ -30681,7 +30684,7 @@ class TextDocumentEdit implements ToJsonable {
   /// The edits to be applied.
   ///  @since 3.16.0 - support for AnnotatedTextEdit. This is guarded by the
   /// client capability `workspace.workspaceEdit.changeAnnotationSupport`
-  final List<Either2<TextEdit, AnnotatedTextEdit>> edits;
+  final List<Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>> edits;
 
   /// The text document to change.
   final OptionalVersionedTextDocumentIdentifier textDocument;
@@ -30726,10 +30729,12 @@ class TextDocumentEdit implements ToJsonable {
           return false;
         }
         if (!((obj['edits'] is List &&
-            (obj['edits'].every((item) => (TextEdit.canParse(item, reporter) ||
-                AnnotatedTextEdit.canParse(item, reporter))))))) {
+            (obj['edits'].every((item) =>
+                (SnippetTextEdit.canParse(item, reporter) ||
+                    AnnotatedTextEdit.canParse(item, reporter) ||
+                    TextEdit.canParse(item, reporter))))))) {
           reporter.reportError(
-              'must be of type List<Either2<TextEdit, AnnotatedTextEdit>>');
+              'must be of type List<Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>>');
           return false;
         }
       } finally {
@@ -30749,8 +30754,9 @@ class TextDocumentEdit implements ToJsonable {
           listEqual(
               edits,
               other.edits,
-              (Either2<TextEdit, AnnotatedTextEdit> a,
-                      Either2<TextEdit, AnnotatedTextEdit> b) =>
+              (Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit> a,
+                      Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>
+                          b) =>
                   a == b) &&
           true;
     }
@@ -31777,6 +31783,9 @@ class TextEdit implements ToJsonable {
     if (AnnotatedTextEdit.canParse(json, nullLspJsonReporter)) {
       return AnnotatedTextEdit.fromJson(json);
     }
+    if (SnippetTextEdit.canParse(json, nullLspJsonReporter)) {
+      return SnippetTextEdit.fromJson(json);
+    }
     final range = json['range'] != null ? Range.fromJson(json['range']) : null;
     final newText = json['newText'];
     return TextEdit(range: range, newText: newText);

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

@@ -78,6 +78,7 @@ class LspClientCapabilities {
   final Set<SymbolKind> workspaceSymbolKinds;
   final Set<CompletionItemKind> completionItemKinds;
   final Set<InsertTextMode> completionInsertTextModes;
+  final bool experimentalSnippetTextEdit;
 
   LspClientCapabilities(this.raw)
       : applyEdit = raw?.workspace?.applyEdit ?? false,
@@ -125,7 +126,10 @@ class LspClientCapabilities {
         workDoneProgress = raw.window?.workDoneProgress ?? false,
         workspaceSymbolKinds = _listToSet(
             raw?.workspace?.symbol?.symbolKind?.valueSet,
-            defaults: defaultSupportedSymbolKinds);
+            defaults: defaultSupportedSymbolKinds),
+        experimentalSnippetTextEdit =
+            raw.experimental is Map<String, dynamic> &&
+                raw.experimental['snippetTextEdit'] == true;
 
   static Set<MarkupKind> _completionDocumentationFormats(
       ClientCapabilities raw) {

pkg/analysis_server/lib/src/lsp/handlers/commands/perform_refactor.dart

@@ -87,7 +87,7 @@ class PerformRefactorCommandHandler extends SimpleEditCommandHandler {
             return fileModifiedError;
           }
 
-          final edit = createWorkspaceEdit(server, change.edits);
+          final edit = createWorkspaceEdit(server, change);
           return await sendWorkspaceEditToClient(edit);
         } on InconsistentAnalysisException {
           return fileModifiedError;

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

@@ -143,7 +143,7 @@ class CodeActionHandler extends MessageHandler<CodeActionParams,
       title: assist.change.message,
       kind: toCodeActionKind(assist.change.id, CodeActionKind.Refactor),
       diagnostics: const [],
-      edit: createWorkspaceEdit(server, assist.change.edits),
+      edit: createWorkspaceEdit(server, assist.change),
     );
   }
 
@@ -156,7 +156,7 @@ class CodeActionHandler extends MessageHandler<CodeActionParams,
       title: fix.change.message,
       kind: toCodeActionKind(fix.change.id, CodeActionKind.QuickFix),
       diagnostics: [diagnostic],
-      edit: createWorkspaceEdit(server, fix.change.edits),
+      edit: createWorkspaceEdit(server, fix.change),
     );
   }
 

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

@@ -146,7 +146,8 @@ class CompletionResolveHandler
         // a command that the client will call to apply those edits later.
         Command command;
         if (otherFilesChanges.isNotEmpty) {
-          final workspaceEdit = createWorkspaceEdit(server, otherFilesChanges);
+          final workspaceEdit =
+              createPlainWorkspaceEdit(server, otherFilesChanges);
           command = Command(
               title: 'Add import',
               command: Commands.sendWorkspaceEdit,

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

@@ -187,7 +187,7 @@ class RenameHandler extends MessageHandler<RenameParams, WorkspaceEdit> {
         return fileModifiedError;
       }
 
-      final workspaceEdit = createWorkspaceEdit(server, change.edits);
+      final workspaceEdit = createWorkspaceEdit(server, change);
       return success(workspaceEdit);
     });
   }

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

@@ -53,7 +53,7 @@ class WillRenameFilesHandler extends MessageHandler<RenameFilesParams, void> {
     }
 
     final change = await refactoring.createChange();
-    final edit = createWorkspaceEdit(server, change.edits);
+    final edit = createWorkspaceEdit(server, change);
 
     return success(edit);
   }

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

@@ -108,10 +108,12 @@ String buildSnippetStringWithTabStops(
   return output.join('');
 }
 
+/// Creates a [lsp.WorkspaceEdit] from simple [server.SourceFileEdit]s.
+///
 /// Note: This code will fetch the version of each document being modified so
 /// it's important to call this immediately after computing edits to ensure
 /// the document is not modified before the version number is read.
-lsp.WorkspaceEdit createWorkspaceEdit(
+lsp.WorkspaceEdit createPlainWorkspaceEdit(
     lsp.LspAnalysisServer server, List<server.SourceFileEdit> edits) {
   return toWorkspaceEdit(
       server.clientCapabilities,
@@ -126,6 +128,52 @@ lsp.WorkspaceEdit createWorkspaceEdit(
           .toList());
 }
 
+/// Creates a [lsp.WorkspaceEdit] from a [server.SourceChange] that can include
+/// experimental [server.SnippetTextEdit]s if the client has indicated support
+/// for these in the experimental section of their client capabilities.
+///
+/// Note: This code will fetch the version of each document being modified so
+/// it's important to call this immediately after computing edits to ensure
+/// the document is not modified before the version number is read.
+lsp.WorkspaceEdit createWorkspaceEdit(
+    lsp.LspAnalysisServer server, server.SourceChange change) {
+  // In order to return snippets, we must ensure we are only modifying a single
+  // existing file with a single edit and that there is a linked edit group with
+  // only one position and no suggestions.
+  if (!server.clientCapabilities.experimentalSnippetTextEdit ||
+      change.edits.length != 1 ||
+      change.edits.first.fileStamp == -1 || // new file
+      change.edits.first.edits.length != 1 ||
+      change.linkedEditGroups.isEmpty ||
+      change.linkedEditGroups.first.positions.length != 1 ||
+      change.linkedEditGroups.first.suggestions.isNotEmpty) {
+    return createPlainWorkspaceEdit(server, change.edits);
+  }
+
+  // Additionally, the selection must fall within the edit offset.
+  final edit = change.edits.first.edits.first;
+  final selectionOffset = change.linkedEditGroups.first.positions.first.offset;
+  final selectionLength = change.linkedEditGroups.first.length;
+
+  if (selectionOffset < edit.offset ||
+      selectionOffset + selectionLength > edit.offset + edit.length) {
+    return createPlainWorkspaceEdit(server, change.edits);
+  }
+
+  return toWorkspaceEdit(
+      server.clientCapabilities,
+      change.edits
+          .map((e) => FileEditInformation(
+                server.getVersionedDocumentIdentifier(e.file),
+                server.getLineInfo(e.file),
+                e.edits,
+                selectionOffsetRelative: selectionOffset - edit.offset,
+                selectionLength: selectionLength,
+                newFile: e.fileStamp == -1,
+              ))
+          .toList());
+}
+
 lsp.CompletionItemKind declarationKindToCompletionItemKind(
   Set<lsp.CompletionItemKind> supportedCompletionKinds,
   dec.DeclarationKind kind,
@@ -1224,6 +1272,21 @@ lsp.SignatureHelp toSignatureHelp(Set<lsp.MarkupKind> preferredFormats,
   );
 }
 
+lsp.SnippetTextEdit toSnippetTextEdit(
+    LspClientCapabilities capabilities,
+    server.LineInfo lineInfo,
+    server.SourceEdit edit,
+    int selectionOffsetRelative,
+    int selectionLength) {
+  assert(selectionOffsetRelative != null);
+  return lsp.SnippetTextEdit(
+    insertTextFormat: lsp.InsertTextFormat.Snippet,
+    range: toRange(lineInfo, edit.offset, edit.length),
+    newText: buildSnippetStringWithTabStops(
+        edit.replacement, [selectionOffsetRelative, selectionLength ?? 0]),
+  );
+}
+
 ErrorOr<server.SourceRange> toSourceRange(
     server.LineInfo lineInfo, Range range) {
   if (range == null) {
@@ -1247,14 +1310,33 @@ ErrorOr<server.SourceRange> toSourceRange(
   return success(server.SourceRange(startOffset, endOffset - startOffset));
 }
 
-lsp.TextDocumentEdit toTextDocumentEdit(FileEditInformation edit) {
+lsp.TextDocumentEdit toTextDocumentEdit(
+    LspClientCapabilities capabilities, FileEditInformation edit) {
   return lsp.TextDocumentEdit(
-    textDocument: edit.doc,
-    edits: edit.edits
-        .map((e) => Either2<lsp.TextEdit, lsp.AnnotatedTextEdit>.t1(
-            toTextEdit(edit.lineInfo, e)))
-        .toList(),
-  );
+      textDocument: edit.doc,
+      edits: edit.edits
+          .map((e) => toTextDocumentEditEdit(capabilities, edit.lineInfo, e,
+              selectionOffsetRelative: edit.selectionOffsetRelative,
+              selectionLength: edit.selectionLength))
+          .toList());
+}
+
+Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>
+    toTextDocumentEditEdit(
+  LspClientCapabilities capabilities,
+  server.LineInfo lineInfo,
+  server.SourceEdit edit, {
+  int selectionOffsetRelative,
+  int selectionLength,
+}) {
+  if (!capabilities.experimentalSnippetTextEdit ||
+      selectionOffsetRelative == null) {
+    return Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>.t3(
+        toTextEdit(lineInfo, edit));
+  }
+  return Either3<lsp.SnippetTextEdit, lsp.AnnotatedTextEdit, lsp.TextEdit>.t1(
+      toSnippetTextEdit(capabilities, lineInfo, edit, selectionOffsetRelative,
+          selectionLength));
 }
 
 lsp.TextEdit toTextEdit(server.LineInfo lineInfo, server.SourceEdit edit) {
@@ -1286,7 +1368,7 @@ lsp.WorkspaceEdit toWorkspaceEdit(
         changes.add(createUnion);
       }
 
-      final textDocEdit = toTextDocumentEdit(edit);
+      final textDocEdit = toTextDocumentEdit(capabilities, edit);
       final textDocEditUnion = Either4<lsp.TextDocumentEdit, lsp.CreateFile,
           lsp.RenameFile, lsp.DeleteFile>.t1(textDocEdit);
       changes.add(textDocEditUnion);

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

@@ -307,6 +307,12 @@ class FileEditInformation {
   final List<server.SourceEdit> edits;
   final bool newFile;
 
+  /// The selection offset, relative to the edit.
+  final int selectionOffsetRelative;
+  final int selectionLength;
+
   FileEditInformation(this.doc, this.lineInfo, this.edits,
-      {this.newFile = false});
+      {this.newFile = false,
+      this.selectionOffsetRelative,
+      this.selectionLength});
 }

pkg/analysis_server/test/lsp/code_actions_assists_test.dart

@@ -2,7 +2,9 @@
 // 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.
 
+import 'package:analysis_server/lsp_protocol/protocol_custom_generated.dart';
 import 'package:analysis_server/lsp_protocol/protocol_generated.dart';
+import 'package:analysis_server/lsp_protocol/protocol_special.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -16,6 +18,15 @@ void main() {
 
 @reflectiveTest
 class AssistsCodeActionsTest extends AbstractCodeActionsTest {
+  @override
+  void setUp() {
+    super.setUp();
+    writePackageConfig(
+      projectFolderPath,
+      flutter: true,
+    );
+  }
+
   Future<void> test_appliesCorrectEdits_withDocumentChangesSupport() async {
     // This code should get an assist to add a show combinator.
     const content = '''
@@ -107,4 +118,171 @@ class AssistsCodeActionsTest extends AbstractCodeActionsTest {
         await getCodeActions(pubspecFileUri.toString(), range: startOfDocRange);
     expect(codeActions, isEmpty);
   }
+
+  Future<void> test_snippetTextEdits_supported() async {
+    // This tests experimental support for including Snippets in TextEdits.
+    // https://github.com/rust-analyzer/rust-analyzer/blob/b35559a2460e7f0b2b79a7029db0c5d4e0acdb44/docs/dev/lsp-extensions.md#snippet-textedit
+    //
+    // This allows setting the cursor position/selection in TextEdits included
+    // in CodeActions, for example Flutter's "Wrap with widget" assist that
+    // should select the text "widget".
+
+    const content = '''
+    import 'package:flutter/widgets.dart';
+    build() {
+      return Container(
+        child: Row(
+          children: [^
+            Text('111'),
+            Text('222'),
+            Container(),
+          ],
+        ),
+      );
+    }
+    ''';
+
+    // For testing, the snippet will be inserted literally into the text, as
+    // this requires some magic on the client. The expected text should therefore
+    // contain the snippets in the standard format.
+    const expectedContent = r'''
+    import 'package:flutter/widgets.dart';
+    build() {
+      return Container(
+        child: Row(
+          children: [
+            ${0:widget}(
+              children: [
+                Text('111'),
+                Text('222'),
+                Container(),
+              ],
+            ),
+          ],
+        ),
+      );
+    }
+    ''';
+
+    newFile(mainFilePath, content: withoutMarkers(content));
+    await initialize(
+      textDocumentCapabilities: withCodeActionKinds(
+          emptyTextDocumentClientCapabilities, [CodeActionKind.Refactor]),
+      workspaceCapabilities:
+          withDocumentChangesSupport(emptyWorkspaceClientCapabilities),
+      experimentalCapabilities: {
+        'snippetTextEdit': true,
+      },
+    );
+
+    final marker = positionFromMarker(content);
+    final codeActions = await getCodeActions(mainFileUri.toString(),
+        range: Range(start: marker, end: marker));
+    final assist = findEditAction(codeActions,
+        CodeActionKind('refactor.flutter.wrap.generic'), 'Wrap with widget...');
+
+    // Ensure the edit came back, and using documentChanges.
+    expect(assist, isNotNull);
+    expect(assist.edit.documentChanges, isNotNull);
+    expect(assist.edit.changes, isNull);
+
+    // Ensure applying the changes will give us the expected content.
+    final contents = {
+      mainFilePath: withoutMarkers(content),
+    };
+    applyDocumentChanges(contents, assist.edit.documentChanges);
+    expect(contents[mainFilePath], equals(expectedContent));
+
+    // Also ensure there was a single edit that was correctly marked
+    // as a SnippetTextEdit.
+    final textEdits = _extractTextDocumentEdits(assist.edit.documentChanges)
+        .expand((tde) => tde.edits)
+        .map((edit) => edit.map(
+              (e) => e,
+              (e) => throw 'Expected SnippetTextEdit, got AnnotatedTextEdit',
+              (e) => throw 'Expected SnippetTextEdit, got TextEdit',
+            ))
+        .toList();
+    expect(textEdits, hasLength(1));
+    expect(textEdits.first.insertTextFormat, equals(InsertTextFormat.Snippet));
+  }
+
+  Future<void> test_snippetTextEdits_unsupported() async {
+    // This tests experimental support for including Snippets in TextEdits
+    // is not active when the client capabilities do not advertise support for it.
+    // https://github.com/rust-analyzer/rust-analyzer/blob/b35559a2460e7f0b2b79a7029db0c5d4e0acdb44/docs/dev/lsp-extensions.md#snippet-textedit
+
+    const content = '''
+    import 'package:flutter/widgets.dart';
+    build() {
+      return Container(
+        child: Row(
+          children: [^
+            Text('111'),
+            Text('222'),
+            Container(),
+          ],
+        ),
+      );
+    }
+    ''';
+
+    newFile(mainFilePath, content: withoutMarkers(content));
+    await initialize(
+      textDocumentCapabilities: withCodeActionKinds(
+          emptyTextDocumentClientCapabilities, [CodeActionKind.Refactor]),
+      workspaceCapabilities:
+          withDocumentChangesSupport(emptyWorkspaceClientCapabilities),
+    );
+
+    final marker = positionFromMarker(content);
+    final codeActions = await getCodeActions(mainFileUri.toString(),
+        range: Range(start: marker, end: marker));
+    final assist = findEditAction(codeActions,
+        CodeActionKind('refactor.flutter.wrap.generic'), 'Wrap with widget...');
+
+    // Ensure the edit came back, and using documentChanges.
+    expect(assist, isNotNull);
+    expect(assist.edit.documentChanges, isNotNull);
+    expect(assist.edit.changes, isNull);
+
+    // Extract just TextDocumentEdits, create/rename/delete are not relevant.
+    final textDocumentEdits =
+        _extractTextDocumentEdits(assist.edit.documentChanges);
+    final textEdits = textDocumentEdits
+        .expand((tde) => tde.edits)
+        .map((edit) => edit.map((e) => e, (e) => e, (e) => e))
+        .toList();
+
+    // Ensure the edit does _not_ have a format of Snippet, nor does it include
+    // any $ characters that would indicate snippet text.
+    for (final edit in textEdits) {
+      expect(edit, isNot(TypeMatcher<SnippetTextEdit>()));
+      expect(edit.newText, isNot(contains(r'$')));
+    }
+  }
+
+  List<TextDocumentEdit> _extractTextDocumentEdits(
+          Either2<
+                  List<TextDocumentEdit>,
+                  List<
+                      Either4<TextDocumentEdit, CreateFile, RenameFile,
+                          DeleteFile>>>
+              documentChanges) =>
+      documentChanges.map(
+        // Already TextDocumentEdits
+        (edits) => edits,
+        // Extract TextDocumentEdits from union of resource changes
+        (changes) => changes
+            .map(
+              (change) => change.map(
+                (textDocEdit) => textDocEdit,
+                (create) => null,
+                (rename) => null,
+                (delete) => null,
+              ),
+            )
+            .where((e) => e != null)
+            .toList(),
+      );
 }

pkg/analysis_server/test/lsp/server_abstract.dart

@@ -650,10 +650,10 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     });
   }
 
-  String applyTextEdit(
-      String content, Either2<TextEdit, AnnotatedTextEdit> change) {
+  String applyTextEdit(String content,
+      Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit> change) {
     // Both sites of the union can cast to TextEdit.
-    final edit = change.map((e) => e, (e) => e);
+    final edit = change.map((e) => e, (e) => e, (e) => e);
     final startPos = edit.range.start;
     final endPos = edit.range.end;
     final lineInfo = LineInfo.fromContent(content);
@@ -714,8 +714,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
       );
 
     for (final change in sortedChanges) {
-      newContent = applyTextEdit(
-          newContent, Either2<TextEdit, AnnotatedTextEdit>.t1(change));
+      newContent = applyTextEdit(newContent,
+          Either3<SnippetTextEdit, AnnotatedTextEdit, TextEdit>.t3(change));
     }
 
     return newContent;
@@ -1217,6 +1217,7 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     TextDocumentClientCapabilities textDocumentCapabilities,
     ClientCapabilitiesWorkspace workspaceCapabilities,
     ClientCapabilitiesWindow windowCapabilities,
+    Map<String, Object> experimentalCapabilities,
     Map<String, Object> initializationOptions,
     bool throwOnFailure = true,
     bool allowEmptyRootUri = false,
@@ -1225,6 +1226,7 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
       workspace: workspaceCapabilities,
       textDocument: textDocumentCapabilities,
       window: windowCapabilities,
+      experimental: experimentalCapabilities,
     );
 
     // Handle any standard incoming requests that aren't test-specific, for example

pkg/analysis_server/tool/lsp_spec/generate_all.dart

@@ -272,6 +272,26 @@ List<AstNode> getCustomClasses() {
       ],
       baseType: 'CompletionItemResolutionInfo',
     ),
+    // Custom types for experimental SnippetTextEdits
+    // https://github.com/rust-analyzer/rust-analyzer/blob/b35559a2460e7f0b2b79a7029db0c5d4e0acdb44/docs/dev/lsp-extensions.md#snippet-textedit
+    interface(
+      'SnippetTextEdit',
+      [
+        field('insertTextFormat', type: 'InsertTextFormat'),
+      ],
+      baseType: 'TextEdit',
+    ),
+    TypeAlias(
+      null,
+      Token.identifier('TextDocumentEditEdits'),
+      ArrayType(
+        UnionType([
+          Type.identifier('SnippetTextEdit'),
+          Type.identifier('AnnotatedTextEdit'),
+          Type.identifier('TextEdit'),
+        ]),
+      ),
+    )
   ];
   return customTypes;
 }

pkg/analysis_server/tool/lsp_spec/typescript.dart

@@ -124,6 +124,9 @@ String getImprovedType(String interfaceName, String fieldName) {
     },
     'ServerCapabilities': {
       'changeNotifications': 'bool',
+    },
+    'TextDocumentEdit': {
+      'edits': 'TextDocumentEditEdits',
     }
   };