feat: add use_nearest_context rule (#190)

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.3.4
+
+- Added `use_nearest_context` rule.
+
 ## 0.3.3
 
 - Fix pub.dev analysis issue

lib/main.dart

@@ -11,6 +11,9 @@ import 'package:solid_lints/src/lints/avoid_returning_widgets/models/avoid_retur
 import 'package:solid_lints/src/lints/double_literal_format/double_literal_format_rule.dart';
 import 'package:solid_lints/src/lints/double_literal_format/fixes/double_literal_format_fix.dart';
 import 'package:solid_lints/src/lints/proper_super_calls/proper_super_calls_rule.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/fixes/rename_nearest_context_parameter_fix.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/fixes/replace_with_nearest_context_parameter_fix.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/use_nearest_context_rule.dart';
 
 /// The entry point for the Solid Lints analyser server plugin.
 ///
@@ -42,6 +45,7 @@ class SolidLintsPlugin extends Plugin {
         analysisOptionsLoader: analysisLoader,
         parametersParser: AvoidReturningWidgetsParameters.fromJson,
       ),
+      UseNearestContextRule(),
     ];
 
     for (final lintRule in lintRules) {
@@ -56,5 +60,15 @@ class SolidLintsPlugin extends Plugin {
       AvoidFinalWithGetterRule.code,
       AvoidFinalWithGetterFix.new,
     );
+
+    registry.registerFixForRule(
+      UseNearestContextRule.code,
+      RenameNearestContextParameterFix.new,
+    );
+
+    registry.registerFixForRule(
+      UseNearestContextRule.code,
+      ReplaceWithNearestContextParameterFix.new,
+    );
   }
 }

lib/src/lints/use_nearest_context/fixes/rename_nearest_context_parameter_fix.dart

@@ -0,0 +1,58 @@
+import 'package:analysis_server_plugin/edit/dart/correction_producer.dart';
+import 'package:analysis_server_plugin/edit/dart/dart_fix_kind_priority.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/use_nearest_context_rule.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/utils/use_nearest_context_utils.dart';
+
+/// A Quick fix for [UseNearestContextRule] rule
+/// Suggests to rename the nearest BuildContext parameter
+/// to the one that is being used.
+class RenameNearestContextParameterFix extends ResolvedCorrectionProducer {
+  static const _renameParameterKind = FixKind(
+    'solid_lints.fix.${UseNearestContextRule.lintName}.rename_parameter',
+    DartFixKindPriority.standard,
+    "Rename nearest BuildContext parameter",
+  );
+
+  /// Creates a new instance of [RenameNearestContextParameterFix].
+  RenameNearestContextParameterFix({required super.context});
+
+  @override
+  FixKind get fixKind => _renameParameterKind;
+
+  @override
+  CorrectionApplicability get applicability =>
+      CorrectionApplicability.automatically;
+
+  @override
+  Future<void> compute(ChangeBuilder builder) async {
+    final identifierNode = node;
+    if (identifierNode is! SimpleIdentifier) return;
+
+    // Do not offer renaming the parameter if this is an access on `this`
+    // or `super`.
+    final parent = identifierNode.parent;
+    if (parent is PropertyAccess) {
+      var target = parent.target;
+      while (target is ParenthesizedExpression) {
+        target = target.expression;
+      }
+      if (target is ThisExpression || target is SuperExpression) return;
+    }
+
+    final closestBuildContext = findClosestBuildContext(identifierNode);
+    if (closestBuildContext == null) return;
+
+    final parameterName = closestBuildContext.name;
+    if (parameterName == null) return;
+
+    await builder.addDartFileEdit(file, (builder) {
+      builder.addSimpleReplacement(
+        parameterName.sourceRange,
+        identifierNode.name,
+      );
+    });
+  }
+}

lib/src/lints/use_nearest_context/fixes/replace_with_nearest_context_parameter_fix.dart

@@ -0,0 +1,68 @@
+import 'package:analysis_server_plugin/edit/dart/correction_producer.dart';
+import 'package:analysis_server_plugin/edit/dart/dart_fix_kind_priority.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/use_nearest_context_rule.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/utils/use_nearest_context_utils.dart';
+
+/// A Quick fix for [UseNearestContextRule] rule
+/// Suggests to replace the outer BuildContext expression
+/// with the nearest available parameter.
+class ReplaceWithNearestContextParameterFix extends ResolvedCorrectionProducer {
+  static const _replaceExpressionKind = FixKind(
+    'solid_lints.fix.${UseNearestContextRule.lintName}.replace_expression',
+    DartFixKindPriority.standard,
+    "Replace with nearest BuildContext parameter",
+  );
+
+  /// Creates a new instance of [ReplaceWithNearestContextParameterFix].
+  ReplaceWithNearestContextParameterFix({required super.context});
+
+  @override
+  FixKind get fixKind => _replaceExpressionKind;
+
+  @override
+  CorrectionApplicability get applicability =>
+      CorrectionApplicability.automatically;
+
+  @override
+  Future<void> compute(ChangeBuilder builder) async {
+    final errorNode = node;
+
+    final closestBuildContext = findClosestBuildContext(errorNode);
+    if (closestBuildContext == null) return;
+
+    final parameterName = closestBuildContext.name?.lexeme;
+    if (parameterName == null) return;
+
+    if (errorNode is ThisExpression) {
+      await builder.addDartFileEdit(file, (builder) {
+        builder.addSimpleReplacement(
+          errorNode.sourceRange,
+          parameterName,
+        );
+      });
+      return;
+    }
+
+    if (errorNode is SimpleIdentifier) {
+      final parent = errorNode.parent;
+      if (parent is PropertyAccess) {
+        var target = parent.target;
+        while (target is ParenthesizedExpression) {
+          target = target.expression;
+        }
+        if (target is ThisExpression || target is SuperExpression) {
+          await builder.addDartFileEdit(file, (builder) {
+            builder.addSimpleReplacement(
+              parent.sourceRange,
+              parameterName,
+            );
+          });
+          return;
+        }
+      }
+    }
+  }
+}

lib/src/lints/use_nearest_context/use_nearest_context_rule.dart

@@ -0,0 +1,82 @@
+import 'package:analyzer/analysis_rule/analysis_rule.dart';
+import 'package:analyzer/analysis_rule/rule_context.dart';
+import 'package:analyzer/analysis_rule/rule_visitor_registry.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/visitors/use_nearest_context_visitor.dart';
+
+/// A rule which checks that we use BuildContext from the nearest available
+/// scope.
+///
+/// ### Example:
+/// #### BAD:
+/// ```dart
+/// class SomeWidget extends StatefulWidget {
+/// ...
+/// }
+///
+/// class _SomeWidgetState extends State<SomeWidget> {
+///   ...
+///   void _showDialog() {
+///     showModalBottomSheet(
+///       context: context,
+///       builder: (BuildContext _) {
+///         final someProvider = context.watch<SomeProvider>(); // LINT, BuildContext is used not from the nearest available scope
+///
+///         return const SizedBox.shrink();
+///       },
+///     );
+///   }
+/// }
+/// ```
+/// #### GOOD:
+/// ```dart
+/// class SomeWidget extends StatefulWidget {
+/// ...
+/// }
+///
+/// class _SomeWidgetState extends State<SomeWidget> {
+///   ...
+///   void _showDialog() {
+///     showModalBottomSheet(
+///       context: context,
+///       builder: (BuildContext context)
+///         final someProvider = context.watch<SomeProvider>(); // OK
+///
+///         return const SizedBox.shrink();
+///       },
+///     );
+///   }
+/// }
+/// ```
+///
+class UseNearestContextRule extends AnalysisRule {
+  /// This lint rule represents the error if BuildContext is used not from the
+  /// nearest available scope
+  static const lintName = 'use_nearest_context';
+
+  /// The code to report for a violation
+  static const LintCode code = LintCode(
+    lintName,
+    'Use the nearest BuildContext parameter instead of the outer one.',
+  );
+
+  /// Creates a new instance of [UseNearestContextRule].
+  UseNearestContextRule()
+      : super(
+          name: lintName,
+          description: code.problemMessage,
+        );
+
+  @override
+  LintCode get diagnosticCode => code;
+
+  @override
+  void registerNodeProcessors(
+    RuleVisitorRegistry registry,
+    RuleContext context,
+  ) {
+    final visitor = UseNearestContextVisitor(this);
+    registry.addSimpleIdentifier(this, visitor);
+    registry.addThisExpression(this, visitor);
+  }
+}

lib/src/lints/use_nearest_context/utils/use_nearest_context_utils.dart

@@ -0,0 +1,23 @@
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:solid_lints/src/utils/types_utils.dart';
+
+/// Finds the closest BuildContext parameter in the AST parent chain of [node].
+SimpleFormalParameter? findClosestBuildContext(AstNode node) {
+  AstNode? current = node.parent;
+
+  while (current != null) {
+    if (current is FunctionExpression) {
+      final functionParams = current.parameters?.parameters ?? [];
+      for (final param in functionParams) {
+        final actualParam =
+            param is DefaultFormalParameter ? param.parameter : param;
+        if (actualParam is SimpleFormalParameter &&
+            isBuildContext(actualParam.declaredFragment?.element.type)) {
+          return actualParam;
+        }
+      }
+    }
+    current = current.parent;
+  }
+  return null;
+}

lib/src/lints/use_nearest_context/visitors/use_nearest_context_visitor.dart

@@ -0,0 +1,74 @@
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/use_nearest_context_rule.dart';
+import 'package:solid_lints/src/lints/use_nearest_context/utils/use_nearest_context_utils.dart';
+import 'package:solid_lints/src/utils/types_utils.dart';
+
+/// A visitor for [UseNearestContextRule].
+class UseNearestContextVisitor extends SimpleAstVisitor<void> {
+  final UseNearestContextRule _rule;
+
+  /// Creates a new instance of [UseNearestContextVisitor].
+  UseNearestContextVisitor(this._rule);
+
+  @override
+  void visitSimpleIdentifier(SimpleIdentifier node) {
+    if (!isBuildContext(node.staticType)) return;
+    if (_isPropertyOfOtherObject(node)) return;
+
+    final closestBuildContext = findClosestBuildContext(node);
+    if (closestBuildContext == null) return;
+    if (closestBuildContext.name?.lexeme != node.name) {
+      if (_isDeclaredInNearestScope(node, closestBuildContext)) return;
+
+      _rule.reportAtNode(node);
+    }
+  }
+
+  @override
+  void visitThisExpression(ThisExpression node) {
+    if (!isBuildContext(node.staticType)) return;
+
+    final closestBuildContext = findClosestBuildContext(node);
+    if (closestBuildContext == null) return;
+
+    _rule.reportAtNode(node);
+  }
+
+  /// Returns `true` if [node] is a property accessed on another object
+  /// (e.g. `state.context`), but not on `this` (e.g. `this.context`).
+  bool _isPropertyOfOtherObject(SimpleIdentifier node) {
+    final parent = node.parent;
+    if (parent is PrefixedIdentifier && node == parent.identifier) {
+      return true;
+    }
+    if (parent is PropertyAccess && node == parent.propertyName) {
+      var target = parent.target;
+      while (target is ParenthesizedExpression) {
+        target = target.expression;
+      }
+      return target is! ThisExpression && target is! SuperExpression;
+    }
+    return false;
+  }
+
+  /// Returns `true` if [node] refers to a variable declared inside the body
+  /// of the function that owns [closestParam] (i.e. a local variable
+  /// in the same scope, like `final localCtx = innerContext;`).
+  bool _isDeclaredInNearestScope(
+    SimpleIdentifier node,
+    SimpleFormalParameter closestParam,
+  ) {
+    final element = node.element;
+    if (element is! LocalVariableElement) return false;
+
+    final nearestFunction = closestParam.parent?.parent;
+    if (nearestFunction is! FunctionExpression) return false;
+
+    final body = nearestFunction.body;
+    final declOffset = element.firstFragment.nameOffset;
+    if (declOffset == null) return false;
+    return declOffset >= body.offset && declOffset < body.end;
+  }
+}

lib/src/utils/types_utils.dart

@@ -129,8 +129,11 @@ bool isRowWidget(DartType? type) => type?.getDisplayString() == 'Row';
 
 bool isPaddingWidget(DartType? type) => type?.getDisplayString() == 'Padding';
 
-bool isBuildContext(DartType? type) =>
-    type?.getDisplayString() == 'BuildContext';
+bool isBuildContext(DartType? type) {
+  if (type == null) return false;
+  final displayString = type.getDisplayString();
+  return displayString == 'BuildContext' || displayString == 'BuildContext?';
+}
 
 bool isGameWidget(DartType? type) => type?.getDisplayString() == 'GameWidget';
 

pubspec.yaml

@@ -2,7 +2,7 @@ name: solid_lints
 description:
   Lints for Dart and Flutter based on software industry standards and best
   practices.
-version: 0.3.3
+version: 0.3.4
 homepage: https://github.com/solid-software/solid_lints/
 documentation: https://solid-software.github.io/solid_lints/docs/intro
 topics: [lints, linter, lint, analysis, analyzer]