Include raw value in Diagnostics json for basic types (#34417)

packages/flutter/lib/src/foundation/diagnostics.dart

@@ -2551,6 +2551,8 @@ class DiagnosticsProperty<T> extends DiagnosticsNode {
     json['defaultLevel'] = describeEnum(_defaultLevel);
     if (value is Diagnosticable || value is DiagnosticsNode)
       json['isDiagnosticableValue'] = true;
+    if (value is num || value is String || value is bool || value == null)
+      json['value'] = value;
     return json;
   }
 

packages/flutter/test/foundation/diagnostics_test.dart

@@ -2098,4 +2098,41 @@ void main() {
         )
     );
   });
+
+  test('DiagnosticsProperty for basic types has value in json', () {
+    DiagnosticsProperty<int> intProperty = DiagnosticsProperty<int>('int1', 10);
+    Map<String, Object> json = simulateJsonSerialization(intProperty);
+    expect(json['name'], 'int1');
+    expect(json['value'], 10);
+
+    intProperty = IntProperty('int2', 20);
+    json = simulateJsonSerialization(intProperty);
+    expect(json['name'], 'int2');
+    expect(json['value'], 20);
+
+    DiagnosticsProperty<double> doubleProperty = DiagnosticsProperty<double>('double', 33.3);
+    json = simulateJsonSerialization(doubleProperty);
+    expect(json['name'], 'double');
+    expect(json['value'], 33.3);
+
+    doubleProperty = DoubleProperty('double2', 33.3);
+    json = simulateJsonSerialization(doubleProperty);
+    expect(json['name'], 'double2');
+    expect(json['value'], 33.3);
+
+    final DiagnosticsProperty<bool> boolProperty = DiagnosticsProperty<bool>('bool', true);
+    json = simulateJsonSerialization(boolProperty);
+    expect(json['name'], 'bool');
+    expect(json['value'], true);
+
+    DiagnosticsProperty<String> stringProperty = DiagnosticsProperty<String>('string1', 'hello');
+    json = simulateJsonSerialization(stringProperty);
+    expect(json['name'], 'string1');
+    expect(json['value'], 'hello');
+
+    stringProperty = StringProperty('string2', 'world');
+    json = simulateJsonSerialization(stringProperty);
+    expect(json['name'], 'string2');
+    expect(json['value'], 'world');
+  });
 }