pkg/linter/lib/src/rules/prefer_spread_collections.dart

// Copyright (c) 2019, 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/analysis_rule/rule_context.dart';
import 'package:analyzer/analysis_rule/rule_visitor_registry.dart';
import 'package:analyzer/dart/ast/visitor.dart';
import 'package:analyzer/error/error.dart';
import 'package:analyzer/src/dart/ast/ast.dart'; // ignore: implementation_imports

import '../analyzer.dart';

const _desc = r'Use spread collections when possible.';

class PreferSpreadCollections extends LintRule {
  PreferSpreadCollections()
    : super(name: LintNames.prefer_spread_collections, description: _desc);

  @override
  DiagnosticCode get diagnosticCode => LinterLintCode.preferSpreadCollections;

  @override
  void registerNodeProcessors(
    RuleVisitorRegistry registry,
    RuleContext context,
  ) {
    var visitor = _Visitor(this);
    registry.addMethodInvocation(this, visitor);
  }
}

class _Visitor extends SimpleAstVisitor<void> {
  final LintRule rule;

  _Visitor(this.rule);

  @override
  void visitMethodInvocation(MethodInvocation invocation) {
    if (invocation.methodName.name != 'addAll' ||
        !invocation.isCascaded ||
        invocation.argumentList.arguments.length != 1) {
      return;
    }

    var cascade = invocation.thisOrAncestorOfType<CascadeExpression>();
    var sections = cascade?.cascadeSections;
    var target = cascade?.target;
    // TODO(pq): add support for Set literals.
    if (target is! ListLiteral ||
        (target is ListLiteralImpl && target.inConstantContext) ||
        (sections != null && sections.first != invocation)) {
      return;
    }

    var argument = invocation.argumentList.arguments.first;
    if (argument is ListLiteral) {
      // Handled by: prefer_inlined_adds
      return;
    }

    rule.reportAtNode(invocation.methodName);
  }
}