使用 dart 中的分析器检查构造函数元素

Question

I created a library in Flutter to generate code for the annotated elements. I need to check the parameter in the constructor of class is required using analyzer.

Example of widget with annotation:

@myAnnotation
class WidgetText extends StatelessWidget {
  WidgetText({
    @required this.text,
    this.subtitle,
  });

  final String text;
  final String subtitle;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text(text),
        if (subtitle != null) Text(subtitle),
      ],
    );
  }
}

Example of my visitor:

class MyAnnotationVisitor extends SimpleElementVisitor<void> {
  @override
  void visitFieldElement(FieldElement element) {
    print('${element.name} is required? ${element.hasRequired}');
  }
}

This visitor above output this for WidgetText

text is required? false
subtitle is required? false

The visitor can verify if the field is required only when an annotation is marked on the field this way below. But is repetitive and I would like to check in the constructor.

@myAnnotation
class WidgetText extends StatelessWidget {
  WidgetText({
    @required this.text,
    this.subtitle,
  });

  @required
  final String text;
  final String subtitle;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text(text),
        if (subtitle != null) Text(subtitle),
      ],
    );
  }
}

Answer 1

This is possible analyzing ParameterElement . Has a get called hasRequired .