[BUG] Dart-dio + Polymorphism + Json_serializable Fails To Produce Polymorphic Classes

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Introduction

In this article, we will explore a bug in the dart-dio generator that prevents it from producing polymorphic classes when used in conjunction with json_serializable. We will also discuss the implications of this bug and provide a potential solution.

Background

The dart-dio generator is a popular tool for generating Dart code from OpenAPI specifications. It allows developers to easily create APIs in Dart, making it a great choice for Flutter developers. However, when used with json_serializable, a library for generating JSON serializable classes, the generator fails to produce polymorphic classes.

The Bug

The bug is demonstrated by the following command:

generate -i swagger.yaml -g dart-dio -o ./_swagger --additional-properties=sourceFolder=openapi/src,pubLibrary=flutter_common.openapi,pubName=flutter_common,serializationLibrary=json_serializable

This command generates the following code:

@JsonSerializable(...)
class Dog { }

However, the expected output is:

@JsonSerializable(...)
class Dog extends Pet { }

As you can see, the Dog class is not extending the Pet class, which is the expected behavior for polymorphic classes.

Implications

This bug has several implications:

  • Immutable classes: When using json_serializable, the generated classes are immutable, which can cause problems when working with other code generators that expect plain old Dart objects.
  • Non-standard constructors: The immutable classes generated by json_serializable have non-standard constructors, which can make it difficult to work with legacy projects that use the -g dart generator.
  • Polymorphism not supported: The -g dart generator does not support polymorphism, which means that developers cannot take advantage of this feature when using this generator.

Potential Solution

To fix this bug, we need to modify the dart-dio generator to produce polymorphic classes when used with json_serializable. This can be achieved by modifying the generator to extend the base class when generating the subclass.

However, before we can implement this fix, we need to understand how the generator works and how to modify it. In the next section, we will provide a guide on how to implement generators.

Implementing Generators

Implementing generators is a complex task that requires a good understanding of the generator's architecture and the code it produces. However, with the right guidance, it is possible to implement a generator that produces polymorphic classes.

Here are the steps to implement a generator:

  1. Understand the generator's architecture: Before we can modify the generator, we need to understand how it works. This includes understanding the code it produces, the inputs it takes, and the outputs it generates.
  2. Identify the problem: Once we understand the generator's architecture, we need to identify the problem that needs to be fixed. In this case, the problem is that the generator fails to produce polymorphic classes when used with json_serializable.
  3. Modify the generator: With the problem identified, we can now modify the generator to produce polymorphic classes. This may involve modifying the code that generates the subclass or adding new code to handle the polymorphism.
  4. Test the generator: Once we have modified the generator, we need to test it to ensure that it produces the correct output. This includes testing the generator with different inputs and verifying that it produces the expected output.

Conclusion

In this article, we have explored a bug in the dart-dio generator that prevents it from producing polymorphic classes when used in conjunction with json_serializable. We have also discussed the implications of this bug and provided a potential solution.

To fix this bug, we need to modify the generator to produce polymorphic classes when used with json_serializable. This can be achieved by modifying the generator to extend the base class when generating the subclass.

However, before we can implement this fix, we need to understand how the generator works and how to modify it. In this article, we have provided a guide on how to implement generators, which should help developers who want to fix this bug.

Future Work

There are several areas where we can improve the generator to make it more useful for developers:

  • Support for more languages: Currently, the generator only supports Dart. However, we can modify it to support other languages, such as Java or Python.
  • Improved error handling: The generator currently does not handle errors well. We can improve it to provide better error messages and handle errors more robustly.
  • More features: We can add more features to the generator, such as support for polymorphism or the ability to generate code for multiple languages at once.

By improving the generator, we can make it more useful for developers and help them to create better APIs.

References

Appendix

Here are some additional resources that may be helpful for developers who want to learn more about generators and how to implement them:

Introduction

In our previous article, we explored a bug in the dart-dio generator that prevents it from producing polymorphic classes when used in conjunction with json_serializable. We also discussed the implications of this bug and provided a potential solution.

In this article, we will answer some frequently asked questions (FAQs) about this bug and provide additional information to help developers who are experiencing this issue.

Q: What is the bug in the dart-dio generator?

A: The bug in the dart-dio generator is that it fails to produce polymorphic classes when used in conjunction with json_serializable. This means that the generated classes do not extend the base class, which is the expected behavior for polymorphic classes.

Q: What are the implications of this bug?

A: The implications of this bug are:

  • Immutable classes: When using json_serializable, the generated classes are immutable, which can cause problems when working with other code generators that expect plain old Dart objects.
  • Non-standard constructors: The immutable classes generated by json_serializable have non-standard constructors, which can make it difficult to work with legacy projects that use the -g dart generator.
  • Polymorphism not supported: The -g dart generator does not support polymorphism, which means that developers cannot take advantage of this feature when using this generator.

Q: How can I fix this bug?

A: To fix this bug, you need to modify the dart-dio generator to produce polymorphic classes when used with json_serializable. This can be achieved by modifying the generator to extend the base class when generating the subclass.

However, before you can implement this fix, you need to understand how the generator works and how to modify it. In our previous article, we provided a guide on how to implement generators, which should help developers who want to fix this bug.

Q: What are the steps to implement a generator?

A: The steps to implement a generator are:

  1. Understand the generator's architecture: Before you can modify the generator, you need to understand how it works. This includes understanding the code it produces, the inputs it takes, and the outputs it generates.
  2. Identify the problem: Once you understand the generator's architecture, you need to identify the problem that needs to be fixed. In this case, the problem is that the generator fails to produce polymorphic classes when used with json_serializable.
  3. Modify the generator: With the problem identified, you can now modify the generator to produce polymorphic classes. This may involve modifying the code that generates the subclass or adding new code to handle the polymorphism.
  4. Test the generator: Once you have modified the generator, you need to test it to ensure that it produces the correct output. This includes testing the generator with different inputs and verifying that it produces the expected output.

Q: What are some additional resources that can help me learn more about generators and how to implement them?

A: Here are some additional resources that can you learn more about generators and how to implement them:

By following these resources, you can learn more about generators and how to implement them, which should help you to fix the bug in the dart-dio generator.

Q: What are some potential solutions to this bug?

A: Here are some potential solutions to this bug:

  • Modify the generator to produce polymorphic classes: This can be achieved by modifying the generator to extend the base class when generating the subclass.
  • Add support for polymorphism to the -g dart generator: This would allow developers to take advantage of polymorphism when using this generator.
  • Improve error handling in the generator: This would make it easier to diagnose and fix issues with the generator.

By implementing one or more of these solutions, you can fix the bug in the dart-dio generator and produce polymorphic classes when used with json_serializable.

Conclusion

In this article, we have answered some frequently asked questions (FAQs) about the bug in the dart-dio generator and provided additional information to help developers who are experiencing this issue. We have also discussed some potential solutions to this bug and provided resources that can help developers learn more about generators and how to implement them.

By following the steps outlined in this article, you should be able to fix the bug in the dart-dio generator and produce polymorphic classes when used with json_serializable.