feat: support context.mounted for use-setstate-synchronously (#1164)

* feat: support context.mounted for use-setstate-synchronously

* test: fix test example

Author: incendial

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 * fix: export missing parts of public API.
+* feat: support `context.mounted` for [`use-setstate-synchronously`](https://dcm.dev/docs/individuals/rules/flutter/use-setstate-synchronously).
 
 ## 5.5.0
 

lib/src/analyzers/lint_analyzer/rules/rules_list/use_setstate_synchronously/helpers.dart

@@ -14,15 +14,15 @@ MountedFact _extractMountedCheck(
   bool permitAnd = true,
   bool expandOr = false,
 }) {
-  // ![this.]mounted
+  // ![this. || context.]mounted
   if (node is PrefixExpression &&
       node.operator.type == TokenType.BANG &&
-      _isIdentifier(_thisOr(node.operand), 'mounted')) {
+      _isIdentifier(_thisOrContextOr(node.operand), 'mounted')) {
     return false.asFact();
   }
 
-  // [this.]mounted
-  if (_isIdentifier(_thisOr(node), 'mounted')) {
+  // [this. || context.]mounted
+  if (_isIdentifier(_thisOrContextOr(node), 'mounted')) {
     return true.asFact();
   }
 
@@ -91,10 +91,17 @@ bool _isDivergent(Statement node, {bool allowControlFlow = false}) =>
     node is ExpressionStatement && node.expression is ThrowExpression;
 
 @pragma('vm:prefer-inline')
-Expression _thisOr(Expression node) =>
-    node is PropertyAccess && node.target is ThisExpression
-        ? node.propertyName
-        : node;
+Expression _thisOrContextOr(Expression node) {
+  if (node is PropertyAccess && node.target is ThisExpression) {
+    return node.propertyName;
+  }
+
+  if (node is PrefixedIdentifier && isBuildContext(node.prefix.staticType)) {
+    return node.identifier;
+  }
+
+  return node;
+}
 
 bool _blockDiverges(Statement block, {required bool allowControlFlow}) => block
         is Block

test/src/analyzers/lint_analyzer/rules/rules_list/use_setstate_synchronously/examples/context_mounted.dart

@@ -0,0 +1,24 @@
+class _FooState extends State<StatefulWidget> {
+  Widget build(BuildContext context) {
+    return FooWidget(
+      onChange: (value) async {
+        setState(() {});
+        await fetchData();
+
+        if (context.mounted) setState(() {});
+      },
+    );
+  }
+}
+
+typedef VoidCallback = void Function();
+
+class State {
+  void setState(VoidCallback callback) {}
+}
+
+class BuildContext {
+  bool get mounted => true;
+}
+
+Future<String> fetchData() => Future.value('123');

test/src/analyzers/lint_analyzer/rules/rules_list/use_setstate_synchronously/use_setstate_synchronously_rule_test.dart

@@ -8,6 +8,8 @@ const _examplePath = 'use_setstate_synchronously/examples/example.dart';
 const _issuesPath = 'use_setstate_synchronously/examples/known_errors.dart';
 const _trySwitchPath =
     'use_setstate_synchronously/examples/extras_try_switch.dart';
+const _contextMountedPath =
+    'use_setstate_synchronously/examples/context_mounted.dart';
 
 void main() {
   group('UseSetStateSynchronouslyTest', () {
@@ -115,5 +117,12 @@ void main() {
         ],
       );
     });
+
+    test('reports no issues for context.mounted', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_contextMountedPath);
+      final issues = UseSetStateSynchronouslyRule().check(unit);
+
+      RuleTestHelper.verifyNoIssues(issues);
+    });
   });
 }