lib/src/rules/sort_child_properties_last.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/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/visitor.dart';

import '../analyzer.dart';
import '../util/flutter_utils.dart';

const _desc = r'Sort child properties last in widget instance creations.';

const _details = r'''
Sort child properties last in widget instance creations.  This improves
readability and plays nicest with UI as Code visualization in IDEs with UI as
Code Guides in editors (such as IntelliJ) where Properties in the correct order 
appear clearly associated with the constructor call and separated from the 
children.

**BAD:**
```
return Scaffold(
  appBar: AppBar(
    title: Text(widget.title),
  ),
  body: Center(
    child: Column(
      children: <Widget>[
        Text(
          'You have pushed the button this many times:',
         ),
        Text(
          '$_counter',
          style: Theme.of(context).textTheme.display1,
         ),
      ],
      mainAxisAlignment: MainAxisAlignment.center,
    ),
    floatingActionButton: FloatingActionButton(
      child: Icon(Icons.add),
      onPressed: _incrementCounter,
      tooltip: 'Increment',
    ),
  ),
);
```

**GOOD:**
```
return Scaffold(
  appBar: AppBar(
    title: Text(widget.title),
  ),
  body: Center(
    floatingActionButton: FloatingActionButton(
      onPressed: _incrementCounter,
      tooltip: 'Increment',
      child: Icon(Icons.add),
    ),
    child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Text(
          'You have pushed the button this many times:',
         ),
        Text(
          '$_counter',
          style: Theme.of(context).textTheme.display1,
         ),
      ],
    ),
  ),
);
```
''';

class SortChildPropertiesLast extends LintRule implements NodeLintRule {
  SortChildPropertiesLast()
      : super(
            name: 'sort_child_properties_last',
            description: _desc,
            details: _details,
            group: Group.style);

  @override
  void registerNodeProcessors(
      NodeLintRegistry registry, LinterContext context) {
    final visitor = _Visitor(this);
    registry.addInstanceCreationExpression(this, visitor);
  }
}

class _Visitor extends SimpleAstVisitor {
  final LintRule rule;

  _Visitor(this.rule);

  @override
  void visitInstanceCreationExpression(InstanceCreationExpression node) {
    if (!isWidgetType(node.staticType)) {
      return;
    }

    var arguments = node.argumentList.arguments;
    if (arguments.length < 2 || isChildArg(arguments.last)) {
      return;
    }

    for (var i = 0; i < arguments.length - 1; ++i) {
      if (isChildArg(arguments[i])) {
        rule.reportLint(arguments[i]);
      }
    }
  }

  static bool isChildArg(Expression e) {
    if (e is NamedExpression) {
      var name = e.name.label.name;
      return (name == 'child' || name == 'children') &&
          isWidgetProperty(e.staticType);
    }
    return false;
  }
}