| // Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| import 'package:analyzer/dart/ast/ast.dart'; |
| import 'package:analyzer/dart/ast/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| |
| import '../analyzer.dart'; |
| import '../util/ascii_utils.dart'; |
| import '../utils.dart'; |
| |
| const _desc = r'Avoid leading underscores for local identifiers.'; |
| |
| const _details = r''' |
| **DON'T** use a leading underscore for identifiers that aren't private. Dart |
| uses a leading underscore in an identifier to mark members and top-level |
| declarations as private. This trains users to associate a leading underscore |
| with one of those kinds of declarations. They see `_` and think "private". |
| There is no concept of "private" for local variables or parameters. When one of |
| those has a name that starts with an underscore, it sends a confusing signal to |
| the reader. To avoid that, don't use leading underscores in those names. |
| |
| **EXCEPTION:**: An unused parameter can be named `_`, `__`, `___`, etc. This is |
| common practice in callbacks where you are passed a value but you don't need |
| to use it. Giving it a name that consists solely of underscores is the idiomatic |
| way to indicate that the value isn't used. |
| |
| **BAD:** |
| ```dart |
| void print(String _name) { |
| var _size = _name.length; |
| ... |
| } |
| ``` |
| **GOOD:** |
| |
| ```dart |
| void print(String name) { |
| var size = name.length; |
| ... |
| } |
| ``` |
| |
| **OK:** |
| |
| ```dart |
| [1,2,3].map((_) => print('Hello')); |
| ``` |
| '''; |
| |
| class NoLeadingUnderscoresForLocalIdentifiers extends LintRule { |
| static const LintCode code = LintCode( |
| 'no_leading_underscores_for_local_identifiers', |
| "The local variable '{0}' starts with an underscore.", |
| correctionMessage: |
| 'Try renaming the variable to not start with an underscore.'); |
| |
| NoLeadingUnderscoresForLocalIdentifiers() |
| : super( |
| name: 'no_leading_underscores_for_local_identifiers', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| LintCode get lintCode => code; |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addCatchClause(this, visitor); |
| registry.addDeclaredIdentifier(this, visitor); |
| registry.addFormalParameterList(this, visitor); |
| registry.addForPartsWithDeclarations(this, visitor); |
| registry.addFunctionDeclarationStatement(this, visitor); |
| registry.addVariableDeclarationStatement(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| void checkIdentifier(Token? id) { |
| if (id == null) return; |
| if (!hasLeadingUnderscore(id.lexeme)) return; |
| if (id.lexeme.isJustUnderscores) return; |
| |
| rule.reportLintForToken(id, arguments: [id.lexeme]); |
| } |
| |
| @override |
| void visitCatchClause(CatchClause node) { |
| checkIdentifier(node.exceptionParameter?.name); |
| checkIdentifier(node.stackTraceParameter?.name); |
| } |
| |
| @override |
| void visitDeclaredIdentifier(DeclaredIdentifier node) { |
| checkIdentifier(node.name); |
| } |
| |
| @override |
| void visitFormalParameterList(FormalParameterList node) { |
| for (var parameter in node.parameters) { |
| if (parameter is DefaultFormalParameter) { |
| parameter = parameter.parameter; |
| } |
| if (parameter is FieldFormalParameter || |
| parameter is SuperFormalParameter) { |
| // These are not local identifiers. |
| return; |
| } |
| if (!parameter.isNamed) { |
| // Named parameters produce a `private_optional_parameter` diagnostic. |
| checkIdentifier(parameter.name); |
| } |
| } |
| } |
| |
| @override |
| void visitForPartsWithDeclarations(ForPartsWithDeclarations node) { |
| for (var variable in node.variables.variables) { |
| checkIdentifier(variable.name); |
| } |
| } |
| |
| @override |
| void visitFunctionDeclarationStatement(FunctionDeclarationStatement node) { |
| checkIdentifier(node.functionDeclaration.name); |
| } |
| |
| @override |
| void visitVariableDeclarationStatement(VariableDeclarationStatement node) { |
| for (var variable in node.variables.variables) { |
| checkIdentifier(variable.name); |
| } |
| } |
| } |