Solving the Autodoc Failure with Nested Pydantic Models in Python

Discover how to fix the `Autodoc` failure when working with nested Pydantic models in your Python project. Follow this guide for a seamless documentation experience.
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Solving the Autodoc Failure with Nested Pydantic Models in Python

If you are developing in Python and using Sphinx to generate documentation, you might encounter an issue when working with nested Pydantic models. Specifically, the error can arise when you try to use the autodoc_pydantic extension in your Sphinx documentation setup. This can be particularly frustrating if you’re trying to leverage the power of Pydantic for data validation and settings management within your classes. Let's break down the problem and how you can easily resolve it.

The Problem

You might find yourself dealing with an AttributeError message that indicates that your class Foo does not have a Config attribute, despite intended use of nested Pydantic models. This typically happens if autodoc_pydantic mistakenly thinks that the outer class is the Pydantic model, while in fact, it is the inner class that inherits from pydantic.BaseModel. Here’s a closer look at your situation:

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However, upon running the make html command, an error ensues, leading to:

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Understanding the Root Cause

At its core, this issue arises from how autodoc_pydantic interprets the hierarchy of your models. It incorrectly identifies the Foo class as a Pydantic model instead of recognizing that only Bar derives from pydantic.BaseModel. This confusion can lead to issues when you include additional Pydantic features, such as validators.

Even further, if you remove the validator method from class Bar, the error vanishes. This suggests that the existence of certain Pydantic features may trigger the misidentification.

The Solution: Update Your Libraries

Upon investigation, the solution to this problem is surprisingly straightforward—updating your autodoc_pydantic package. As of version 1.7.2 and later, this issue has been addressed and should function correctly with nested models. Here’s how you can update it:

Open your terminal or command prompt.

Use pip to upgrade the package with the following command:

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After upgrading, rebuild your documentation by running:

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By following these steps, you should find that the AttributeError no longer appears, and your documentation generation process works seamlessly.

Conclusion

Dealing with documentation in Python projects, especially with nested models, can sometimes be fraught with challenges. However, by keeping your dependencies updated, you can often sidestep many of the issues that can arise. If you find yourself stuck in the future, remember to check for updates and refer to the documentation of the packages you're using. Happy coding and documenting!