feat: Add conditional widget with expression evaluation support

examples/stac_gallery/assets/json/home_screen.json

@@ -1373,5 +1373,27 @@
         "assetPath": "assets/json/variable_example.json"
       }
     }
+  },
+  {
+    "type": "listTile",
+    "leading": {
+      "type": "icon",
+      "icon": "code"
+    },
+    "title": {
+      "type": "text",
+      "data": "Conditional Rendering"
+    },
+    "subtitle": {
+      "type": "text",
+      "data": "Use if-else conditions in STAC templates"
+    },
+    "onTap": {
+      "actionType": "navigate",
+      "widgetJson": {
+        "type": "exampleScreen",
+        "assetPath": "assets/json/conditional_example.json"
+      }
+    }
   }
 ]

examples/stac_gallery/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -26,6 +26,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      customLLDBInitFile = "$(SRCROOT)/Flutter/ephemeral/flutter_lldbinit"
       shouldUseLaunchSchemeArgsEnv = "YES">
       <MacroExpansion>
          <BuildableReference
@@ -54,6 +55,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      customLLDBInitFile = "$(SRCROOT)/Flutter/ephemeral/flutter_lldbinit"
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"

packages/stac/lib/src/framework/stac.dart

@@ -106,6 +106,7 @@ class Stac {
     const StacGestureDetectorParser(),
     const StacSetValueParser(),
     const StacInkwellParser(),
+    const StacConditionalParser(),
   ];
 
   static final _actionParsers = <StacActionParser>[

packages/stac/lib/src/parsers/widgets/stac_conditional/stac_conditional.dart

@@ -0,0 +1,19 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+import 'package:stac_framework/stac_framework.dart';
+
+export 'stac_conditional_parser.dart';
+
+part 'stac_conditional.freezed.dart';
+part 'stac_conditional.g.dart';
+
+@freezed
+abstract class StacConditional with _$StacConditional {
+  const factory StacConditional({
+    required String condition,
+    required StacWidget ifTrue,
+    StacWidget? ifFalse,
+  }) = _StacConditional;
+
+  factory StacConditional.fromJson(Map<String, dynamic> json) =>
+      _$StacConditionalFromJson(json);
+}

packages/stac/lib/src/parsers/widgets/stac_conditional/stac_conditional_parser.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+import 'package:stac/src/framework/stac.dart';
+import 'package:stac/src/parsers/widgets/stac_conditional/stac_conditional.dart';
+import 'package:stac/src/utils/expression_resolver.dart';
+import 'package:stac/src/utils/widget_type.dart';
+import 'package:stac_framework/stac_framework.dart';
+
+class StacConditionalParser extends StacParser<StacConditional> {
+  const StacConditionalParser();
+
+  @override
+  String get type => WidgetType.conditional.name;
+
+  @override
+  StacConditional getModel(StacWidget json) => StacConditional.fromJson(json);
+
+  @override
+  Widget parse(BuildContext context, StacConditional model) {
+    final result = ExpressionResolver.evaluate(model.condition);
+    if (result) {
+      return Stac.fromJson(model.ifTrue, context) ?? const SizedBox();
+    } else if (model.ifFalse != null) {
+      return Stac.fromJson(model.ifFalse, context) ?? const SizedBox();
+    }
+    return const SizedBox();
+  }
+}

packages/stac/lib/src/parsers/widgets/stac_dynamic_view/stac_dynamic_view_parser.dart

@@ -217,10 +217,9 @@ class StacDynamicViewParser extends StacParser<StacDynamicView> {
 
               // Extract the value from the data
               final dataValue = _extractNestedData(data, keys);
-              if (dataValue != null) {
-                processedValue = processedValue.replaceAll(
-                    placeholder, dataValue.toString());
-              }
+
+              processedValue =
+                  processedValue.replaceAll(placeholder, dataValue.toString());
             }
 
             template[key] = processedValue;

packages/stac/lib/src/parsers/widgets/widgets.dart

@@ -27,6 +27,7 @@ export 'package:stac/src/parsers/widgets/stac_clip_oval/stac_clip_oval.dart';
 export 'package:stac/src/parsers/widgets/stac_clip_rrect/stac_clip_rrect.dart';
 export 'package:stac/src/parsers/widgets/stac_colored_box/stac_colored_box.dart';
 export 'package:stac/src/parsers/widgets/stac_column/stac_column.dart';
+export 'package:stac/src/parsers/widgets/stac_conditional/stac_conditional.dart';
 export 'package:stac/src/parsers/widgets/stac_container/stac_container.dart';
 export 'package:stac/src/parsers/widgets/stac_custom_scroll_view/stac_custom_scroll_view.dart';
 export 'package:stac/src/parsers/widgets/stac_decoration_image/stac_decoration_image.dart';