Remove Internal Pubsub Types From Public API: A Guide

by Alex Johnson 54 views

It's crucial to maintain a clean and well-defined public API for any software library or service. This ensures that users interact with the intended functionalities and avoids exposing internal workings that might be subject to change or are not meant for external consumption. In the context of Google Cloud Pub/Sub, ensuring that internal-only types are not exposed in the public API is essential for maintaining stability and clarity. This article delves into the reasons, challenges, and methods for removing such internal types, focusing on a specific scenario involving the google-cloud-rust library.

The Importance of a Clean Public API

Your public API is the face of your library or service. It's the contract you make with your users, defining how they can interact with your system. A clean and well-defined API offers numerous benefits:

  • Usability: A clear API is easier to understand and use. Developers can quickly grasp the intended functionality and how to achieve their goals.
  • Stability: By exposing only stable and well-defined types and functions, you reduce the risk of breaking changes. Internal types, on the other hand, are more likely to change as the implementation evolves.
  • Maintainability: A clean API simplifies maintenance and refactoring. Changes to internal implementations are less likely to affect external users.
  • Security: Hiding internal types can prevent users from accessing functionalities that are not intended for public use, thereby improving security.

In the case of Pub/Sub, a messaging service, exposing internal types could lead to confusion and potential misuse. Users might inadvertently rely on internal structures that are not guaranteed to remain stable, leading to unexpected issues in the future. Therefore, actively removing these internal types is a crucial step in maintaining a robust and user-friendly API.

The Challenge: Exposing Builders for Doctests

One common challenge in software development is ensuring that code examples in documentation (doctests) are working correctly. Doctests are a great way to demonstrate the usage of your API and ensure that the examples remain up-to-date with the code. However, sometimes, achieving this requires exposing internal parts of your code, such as builder types, which are used to construct complex objects.

In the google-cloud-rust library, builders might have been exposed using the #[doc(hidden)] tag as a workaround for doctest failures. This tag hides the types from the generated documentation but doesn't prevent them from being used in the code. While this approach solves the immediate problem of doctests, it leaves the internal types exposed in the public API, which, as discussed earlier, is not ideal.

The reason this happens is often due to the doctests needing to construct complex objects that rely on internal structures. For example, a Pub/Sub message might have several attributes or configurations that are managed by a builder. If the builder itself is not part of the public API, it becomes difficult to create these objects within the doctests without exposing internal details.

The Solution: Sidekick Configuration and API Cleanup

The preferred solution to this problem involves a combination of sidekick configuration and API cleanup. Sidekick, in this context, likely refers to a tool or process used to manage and generate the API documentation and potentially other aspects of the library's build process. By configuring sidekick appropriately, we can address the doctest issue without exposing internal types in the public API.

The steps involved in this solution are:

  1. Identify the Internal Types: The first step is to clearly identify the types that are internal-only and should not be part of the public API. These are often builder types or other implementation-specific structures.
  2. Configure Sidekick: The sidekick configuration should be adjusted to handle doctests correctly without requiring the exposure of internal types. This might involve creating separate test fixtures or using alternative methods for constructing objects within the doctests.
  3. Remove Types from Public API: Once sidekick is configured, the internal types should be removed from the public API. This means ensuring that they are not accessible from the public modules and are not included in the generated documentation.
  4. Verify and Test: After removing the types, it's crucial to verify that the API still functions as expected and that the doctests pass without errors. This step ensures that the changes haven't introduced any regressions.

This approach ensures that the library's API remains clean and stable while still allowing for effective documentation and testing.

Diving Deeper: Implementing the Solution

To implement the solution effectively, let's break down each step in more detail:

1. Identifying Internal Types

The process of identifying internal types involves reviewing the codebase and identifying structures that are not intended for public use. These might include:

  • Builder Types: As mentioned earlier, builder types are often used to construct complex objects but are not meant to be part of the public API.
  • Implementation-Specific Structures: These are types that are used internally within the library's implementation and are not relevant to users.
  • Types Marked with #[doc(hidden)]: While this tag hides the types from documentation, it's a good starting point for identifying potentially internal types.

Carefully examine each type and consider its purpose and intended audience. If a type is only used within the library's implementation and doesn't provide any value to external users, it's likely an internal type.

2. Configuring Sidekick

Configuring sidekick might involve several steps, depending on the specific tool and its capabilities. Some common approaches include:

  • Creating Test Fixtures: Instead of exposing builders, you can create test fixtures that provide pre-constructed objects for use in doctests. These fixtures can use internal builders or other mechanisms to create the objects, but they are not part of the public API.
  • Using Alternative Construction Methods: If possible, provide public methods or functions that allow users to construct the necessary objects without relying on internal builders. This might involve adding factory methods or providing a more user-friendly API for object creation.
  • Configuring Doctest Environment: Some tools allow you to configure the doctest environment to include internal modules or functions. This can be a convenient way to access internal types within doctests without exposing them in the public API.

The specific configuration will depend on the sidekick tool and the structure of the google-cloud-rust library. Consult the sidekick documentation and the library's build process for guidance.

3. Removing Types from the Public API

Once sidekick is configured, the next step is to remove the internal types from the public API. This typically involves the following:

  • Removing Public Exports: Ensure that the internal types are not exported from any public modules. This prevents users from accessing them directly.
  • Adjusting Module Structure: You might need to reorganize the module structure to ensure that internal types are located in private modules that are not accessible from the outside.
  • Verifying API Surface: Use tools or manual inspection to verify that the internal types are no longer part of the public API surface.

This step is crucial for maintaining a clean and stable API. Be careful to avoid accidentally removing types that are intended for public use.

4. Verifying and Testing

After removing the internal types, it's essential to verify that the changes haven't introduced any regressions. This involves:

  • Running Doctests: Ensure that all doctests pass without errors. This confirms that the changes to sidekick configuration and API structure haven't broken the documentation examples.
  • Running Unit Tests: Run all unit tests to verify that the library's functionality remains intact. This helps to catch any unexpected side effects of the changes.
  • Manual Testing: Perform manual testing to ensure that the API behaves as expected from a user's perspective. This might involve writing sample code that uses the public API to perform common tasks.

Thorough testing is crucial for ensuring that the changes have been successful and haven't introduced any new issues.

Conclusion

Removing internal types from the public API is an important step in maintaining a clean, stable, and user-friendly library. By using a combination of sidekick configuration and API cleanup, you can address the challenges of doctests and ensure that your API remains well-defined and easy to use. The process involves identifying internal types, configuring sidekick to handle doctests, removing the types from the public API, and thoroughly verifying and testing the changes.

By following these steps, the google-cloud-rust library can provide a better experience for its users and ensure the long-term stability and maintainability of the API. Remember, a well-defined API is an investment in the future of your library or service. For more information on best practices for API design and maintenance, consider exploring resources from trusted sources like Microsoft's API Design Guide.