Add new WidgetInspector service extension: getRootWidgetTree (flutter#150010)

The new service extension `getRootWidgetTree` can be used instead of the existing:

* `getRootWidgetSummaryTree` -->  use`getRootWidgetTree` with parameters `isSummaryTree=true`
* `getRootWidgetSummaryTreeWithPreviews` --> use `getRootWidgetTree` with parameters `isSummaryTree=true` and `withPreviews=true`

This new service extension will enable Flutter DevTools to combine the widget summary tree with the widget details tree by calling `getRootWidgetTree` with `isSummary=false` and `withPreviews=true`. 

Closes flutter/devtools#7894

Author: elliette

packages/flutter/lib/src/widgets/service_extensions.dart

@@ -366,6 +366,22 @@ enum WidgetInspectorServiceExtensions {
   ///   extension is registered.
   getRootWidget,
 
+  /// Name of service extension that, when called, will return the
+  /// [DiagnosticsNode] data for the root [Element] of the widget tree.
+  ///
+  /// If the parameter `isSummaryTree` is true, the tree will only include
+  /// [Element]s that were created by user code.
+  ///
+  /// If the parameter `withPreviews` is true, text previews will be included
+  /// for [Element]s with a corresponding [RenderObject] of type
+  /// [RenderParagraph].
+  ///
+  /// See also:
+  ///
+  /// * [WidgetInspectorService.initServiceExtensions], where the service
+  ///   extension is registered.
+  getRootWidgetTree,
+
   /// Name of service extension that, when called, will return the
   /// [DiagnosticsNode] data for the root [Element] of the summary tree, which
   /// only includes [Element]s that were created by user code.

packages/flutter/lib/src/widgets/widget_inspector.dart

@@ -1255,6 +1255,11 @@ mixin WidgetInspectorService {
       callback: _getRootWidgetSummaryTreeWithPreviews,
       registerExtension: registerExtension,
     );
+    registerServiceExtension(
+      name: WidgetInspectorServiceExtensions.getRootWidgetTree.name,
+      callback: _getRootWidgetTree,
+      registerExtension: registerExtension,
+    );
     registerServiceExtension(
       name: WidgetInspectorServiceExtensions.getDetailsSubtree.name,
       callback: (Map<String, String> parameters) async {
@@ -1951,42 +1956,93 @@ mixin WidgetInspectorService {
     String groupName, {
     Map<String, Object>? Function(DiagnosticsNode, InspectorSerializationDelegate)? addAdditionalPropertiesCallback,
   }) {
-    return _nodeToJson(
-      WidgetsBinding.instance.rootElement?.toDiagnosticsNode(),
-      InspectorSerializationDelegate(
-        groupName: groupName,
-        subtreeDepth: 1000000,
-        summaryTree: true,
-        service: this,
-        addAdditionalPropertiesCallback: addAdditionalPropertiesCallback,
-      ),
+    return _getRootWidgetTreeImpl(
+      groupName: groupName,
+      isSummaryTree: true,
+      withPreviews: false,
+      addAdditionalPropertiesCallback: addAdditionalPropertiesCallback,
     );
   }
 
-
   Future<Map<String, Object?>> _getRootWidgetSummaryTreeWithPreviews(
     Map<String, String> parameters,
   ) {
     final String groupName = parameters['groupName']!;
-    final Map<String, Object?>? result = _getRootWidgetSummaryTree(
-      groupName,
-      addAdditionalPropertiesCallback: (DiagnosticsNode node, InspectorSerializationDelegate? delegate) {
-        final Map<String, Object> additionalJson = <String, Object>{};
-        final Object? value = node.value;
-        if (value is Element) {
-          final RenderObject? renderObject = value.renderObject;
-          if (renderObject is RenderParagraph) {
-            additionalJson['textPreview'] = renderObject.text.toPlainText();
-          }
-        }
-        return additionalJson;
-      },
+    final Map<String, Object?>? result = _getRootWidgetTreeImpl(
+      groupName: groupName,
+      isSummaryTree: true,
+      withPreviews: true,
     );
     return Future<Map<String, dynamic>>.value(<String, dynamic>{
       'result': result,
     });
   }
 
+  Future<Map<String, Object?>> _getRootWidgetTree(
+    Map<String, String> parameters,
+  ) {
+    final String groupName = parameters['groupName']!;
+    final bool isSummaryTree = parameters['isSummaryTree'] == 'true';
+    final bool withPreviews = parameters['withPreviews'] == 'true';
+
+    final Map<String, Object?>? result = _getRootWidgetTreeImpl(
+      groupName: groupName,
+      isSummaryTree: isSummaryTree,
+      withPreviews: withPreviews,
+    );
+
+    return Future<Map<String, dynamic>>.value(<String, dynamic>{
+      'result': result,
+    });
+  }
+
+  Map<String, Object?>? _getRootWidgetTreeImpl({
+    required String groupName,
+    required bool isSummaryTree,
+    required bool withPreviews,
+    Map<String, Object>? Function(
+            DiagnosticsNode, InspectorSerializationDelegate)?
+        addAdditionalPropertiesCallback,
+  }) {
+    final bool shouldAddAdditionalProperties =
+        addAdditionalPropertiesCallback != null || withPreviews;
+
+    // Combine the given addAdditionalPropertiesCallback with logic to add text
+    // previews as well (if withPreviews is true):
+    Map<String, Object>? combinedAddAdditionalPropertiesCallback(
+      DiagnosticsNode node,
+      InspectorSerializationDelegate delegate,
+    ) {
+      final Map<String, Object> additionalPropertiesJson =
+          addAdditionalPropertiesCallback?.call(node, delegate) ??
+              <String, Object>{};
+      if (!withPreviews) {
+        return additionalPropertiesJson;
+      }
+      final Object? value = node.value;
+      if (value is Element) {
+        final RenderObject? renderObject = value.renderObject;
+        if (renderObject is RenderParagraph) {
+          additionalPropertiesJson['textPreview'] =
+              renderObject.text.toPlainText();
+        }
+      }
+      return additionalPropertiesJson;
+    }
+    return _nodeToJson(
+      WidgetsBinding.instance.rootElement?.toDiagnosticsNode(),
+      InspectorSerializationDelegate(
+        groupName: groupName,
+        subtreeDepth: 1000000,
+        summaryTree: isSummaryTree,
+        service: this,
+        addAdditionalPropertiesCallback: shouldAddAdditionalProperties
+            ? combinedAddAdditionalPropertiesCallback
+            : null,
+      ),
+    );
+  }
+
   /// Returns a JSON representation of the subtree rooted at the
   /// [DiagnosticsNode] object that `diagnosticsNodeId` references providing
   /// information needed for the details subtree view.

packages/flutter/test/foundation/service_extensions_test.dart

@@ -166,7 +166,7 @@ void main() {
   tearDownAll(() async {
     // See widget_inspector_test.dart for tests of the ext.flutter.inspector
     // service extensions included in this count.
-    int widgetInspectorExtensionCount = 28;
+    int widgetInspectorExtensionCount = 29;
     if (WidgetInspectorService.instance.isWidgetCreationTracked()) {
       // Some inspector extensions are only exposed if widget creation locations
       // are tracked.