Make attribute value final

lib/models/documents/attribute.dart

@@ -9,12 +9,9 @@ enum AttributeScope {
 class Attribute<T> {
   final String key;
   final AttributeScope scope;
-  T _value;
+  final T value;
 
-  Attribute(this.key, this.scope, this._value);
-
-  T getValue() => _value;
-  setValue(T val) => _value = val;
+  Attribute(this.key, this.scope, this.value);
 
   static final Map<String, Attribute> _registry = {
     Attribute.bold.key: Attribute.bold,
@@ -63,22 +60,19 @@ class Attribute<T> {
   bool get isBlockExceptHeader =>
       scope == AttributeScope.BLOCK && key != Attribute.header.key;
 
-  Map<String, dynamic> toJson() => <String, dynamic>{key: _value};
+  Map<String, dynamic> toJson() => <String, dynamic>{key: value};
 
   static Attribute fromKeyValue(String key, dynamic value) {
     if (!_registry.containsKey(key)) {
       throw ArgumentError.value(key, 'key "$key" not found.');
     }
     Attribute origin = _registry[key];
-    Attribute attribute = clone(origin);
-    if (value != null) {
-      attribute.setValue(value);
-    }
+    Attribute attribute = clone(origin, value);
     return attribute;
   }
   
-  static Attribute clone(Attribute origin) {
-    return Attribute(origin.key, origin.scope, origin.getValue());
+  static Attribute clone(Attribute origin, dynamic value) {
+    return Attribute(origin.key, origin.scope, value);
   }
 
   @override
@@ -88,15 +82,15 @@ class Attribute<T> {
     Attribute<T> typedOther = other;
     return key == typedOther.key &&
         scope == typedOther.scope &&
-        _value == typedOther._value;
+        value == typedOther.value;
   }
 
   @override
-  int get hashCode => hash3(key, scope, _value);
+  int get hashCode => hash3(key, scope, value);
 
   @override
   String toString() {
-    return 'Attribute{key: $key, scope: $scope, value: $_value}';
+    return 'Attribute{key: $key, scope: $scope, value: $value}';
   }
 }
 

lib/models/documents/nodes/line.dart

@@ -168,7 +168,7 @@ class Line extends Container<Leaf> {
 
     if (parent is Block) {
       Attribute parentStyle = (parent as Block).style.getBlockExceptHeader();
-      if (blockStyle.getValue() == null) {
+      if (blockStyle.value == null) {
         _unwrap();
       } else if (blockStyle != parentStyle) {
         _unwrap();
@@ -177,7 +177,7 @@ class Line extends Container<Leaf> {
         _wrap(block);
         block.adjust();
       }
-    } else if (blockStyle.getValue() != null) {
+    } else if (blockStyle.value != null) {
       Block block = Block();
       block.applyAttribute(blockStyle);
       _wrap(block);

lib/models/documents/style.dart

@@ -24,8 +24,8 @@ class Style {
 
   Map<String, dynamic> toJson() => _attributes.isEmpty
       ? null
-      : _attributes.map<String, dynamic>((String _, Attribute value) =>
-          MapEntry<String, dynamic>(value.key, value.getValue()));
+      : _attributes.map<String, dynamic>((String _, Attribute attribute) =>
+          MapEntry<String, dynamic>(attribute.key, attribute.value));
 
   Iterable<String> get keys => _attributes.keys;
 
@@ -54,7 +54,7 @@ class Style {
 
   Style merge(Attribute attribute) {
     Map<String, Attribute> merged = Map<String, Attribute>.from(_attributes);
-    if (attribute.getValue() == null) {
+    if (attribute.value == null) {
       merged.remove(attribute.key);
     } else {
       merged[attribute.key] = attribute;

lib/models/rules/insert.dart

@@ -79,7 +79,7 @@ class PreserveBlockStyleOnInsertRule extends InsertRule {
       return null;
     }
 
-    var blockStyle = <String, dynamic>{attribute.key: attribute.getValue()};
+    var blockStyle = <String, dynamic>{attribute.key: attribute.value};
 
     Map<String, dynamic> resetStyle;
 

lib/widgets/editor.dart

@@ -298,7 +298,7 @@ class _QuillEditorSelectionGestureDetectorBuilder
       if (getEditor().widget.readOnly) {
         getEditor()
             .widget
-            .onLaunchUrl(segment.style.attributes[Attribute.link.key].getValue());
+            .onLaunchUrl(segment.style.attributes[Attribute.link.key].value);
       }
     }
   }

lib/widgets/raw_editor.dart

@@ -609,7 +609,7 @@ class RawEditorState extends EditorState
       Line line, DefaultStyles defaultStyles) {
     Map<String, Attribute> attrs = line.style.attributes;
     if (attrs.containsKey(Attribute.header.key)) {
-      int level = attrs[Attribute.header.key].getValue();
+      int level = attrs[Attribute.header.key].value;
       switch (level) {
         case 1:
           return defaultStyles.h1.verticalSpacing;

lib/widgets/text_block.dart

@@ -145,7 +145,7 @@ class EditableTextBlock extends StatelessWidget {
 
     Map<String, Attribute> attrs = block.style.attributes;
     if (attrs.containsKey(Attribute.header.key)) {
-      int level = attrs[Attribute.header.key].getValue();
+      int level = attrs[Attribute.header.key].value;
       switch (level) {
         case 1:
           top = defaultStyles.h1.verticalSpacing.item1;