Computed variables: VariableData.formula

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AjsYaRkTHNKszSHjd3j264

Author: claude

lib/src/api/models/variables_model.dart

@@ -114,13 +114,24 @@ class VariableData
   /// metadata or any other information that is not part of the core variable.
   final Map<String, dynamic> extra;
 
+  /// A formula expression (what goes inside `${= ...}`) that computes this
+  /// variable's value from other variables, e.g. `fresh < freshLimit`. Empty
+  /// for a variable that holds a value. A computed variable is read-only:
+  /// actions that set it are ignored, and it changes whenever a variable its
+  /// formula reads changes.
+  final String formula;
+
+  /// Whether this variable's value comes from [formula].
+  bool get isComputed => formula.trim().isNotEmpty;
+
   /// Creates a new [VariableData].
   VariableData({
     required this.id,
     required this.name,
     Object? value = '',
     this.type = VariableType.text,
     Map<String, dynamic>? extra,
+    this.formula = '',
   }) : value = sanitizeValueForVariableType(value, type) ?? '',
        extra = extra ?? {};
 
@@ -133,6 +144,7 @@ class VariableData
     bool? isUsed,
     Set<String>? nodes,
     Map<String, dynamic>? extra,
+    String? formula,
   }) {
     final String? sanitizedValue = value == null
         ? null
@@ -143,11 +155,12 @@ class VariableData
       value: sanitizedValue ?? this.value,
       type: type ?? this.type,
       extra: extra ?? this.extra,
+      formula: formula ?? this.formula,
     );
   }
 
   @override
-  List<Object?> get props => [id, name, value, type];
+  List<Object?> get props => [id, name, value, type, formula];
 
   @override
   int compareTo(VariableData other) => name.compareTo(other.name);
@@ -168,6 +181,7 @@ class VariableData
     name: name,
     value: value,
     type: type,
+    formula: formula,
   );
 
   /// Returns the value converted to the appropriate type according to [type].
@@ -243,6 +257,7 @@ class CanvasVariableData extends VariableData {
     super.type,
     super.value,
     super.extra,
+    super.formula,
   });
 
   @override
@@ -255,6 +270,7 @@ class CanvasVariableData extends VariableData {
     String? canvasId,
     Set<String>? nodes,
     Map<String, dynamic>? extra,
+    String? formula,
   }) {
     final String? sanitizedValue = value == null
         ? null
@@ -266,6 +282,7 @@ class CanvasVariableData extends VariableData {
       id: id ?? this.id,
       canvasId: canvasId ?? this.canvasId,
       extra: extra ?? this.extra,
+      formula: formula ?? this.formula,
     );
   }
 
@@ -301,6 +318,7 @@ class RuntimeVariableData extends VariableData {
     super.value = '',
     super.type = VariableType.text,
     super.extra,
+    super.formula,
   }) : super(id: id ?? generateId());
 
   @override
@@ -312,6 +330,7 @@ class RuntimeVariableData extends VariableData {
     bool? isUsed,
     Set<String>? nodes,
     Map<String, dynamic>? extra,
+    String? formula,
   }) {
     final String? sanitizedValue = value == null
         ? null
@@ -322,6 +341,7 @@ class RuntimeVariableData extends VariableData {
       value: sanitizedValue ?? this.value,
       type: type ?? this.type,
       extra: extra ?? this.extra,
+      formula: formula ?? this.formula,
     );
   }
 }

lib/src/api/models/variables_model.g.dart

@@ -0,0 +1,24 @@
+import 'package:codelessly_api/codelessly_api.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('a computed variable round-trips its formula', () {
+    final variable = VariableData(
+      id: 'over',
+      name: 'over',
+      type: VariableType.boolean,
+      formula: 'level > limit',
+    );
+    final back = VariableData.fromJson(variable.toJson());
+    expect(back, variable);
+    expect(back.isComputed, isTrue);
+    expect(variable.withCanvas('c').formula, 'level > limit');
+    expect(variable.copyWith(name: 'x').formula, 'level > limit');
+  });
+
+  test('a plain variable stores no formula', () {
+    final json = VariableData(id: 'a', name: 'a', value: '1').toJson();
+    expect(json.containsKey('formula'), isFalse);
+    expect(VariableData.fromJson(json).isComputed, isFalse);
+  });
+}