How To Remove Onyx.connect() For ONYXKEYS.NVP_INTRO_SELECTED In Src/libs/SubscriptionUtils.ts

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This article details the process of removing Onyx.connect() for the key ONYXKEYS.NVP_INTRO_SELECTED within the src/libs/SubscriptionUtils.ts module. This task is part of a larger initiative to deprecate Onyx.connect and modernize the application's data handling mechanisms. The approach emphasizes test-driven development (TDD) to ensure code reliability and maintainability throughout the refactoring process. This article provides a comprehensive guide on the steps involved, the rationale behind them, and the importance of thorough testing.

Understanding the Context: Deprecating Onyx.connect

The primary goal of this refactoring effort is to deprecate the use of Onyx.connect. Onyx.connect is a method used to connect React components to Onyx, a persistent data store used within the Expensify application. While Onyx.connect has served its purpose, newer approaches offer improved performance, maintainability, and scalability. Deprecating Onyx.connect involves systematically identifying and replacing its usages with alternative data fetching and management techniques. This particular task focuses on removing the connection associated with the ONYXKEYS.NVP_INTRO_SELECTED key within the src/libs/SubscriptionUtils.ts module.

The Parent Issue provides broader context and outlines the overall strategy for this deprecation effort. Understanding the parent issue is crucial for grasping the significance of individual tasks like this one and ensuring that the changes align with the larger architectural goals of the project.

Identifying the Target: src/libs/SubscriptionUtils.ts and ONYXKEYS.NVP_INTRO_SELECTED

The specific module targeted in this task is src/libs/SubscriptionUtils.ts. This module likely contains utility functions related to subscription management within the Expensify application. The key ONYXKEYS.NVP_INTRO_SELECTED is used to store a boolean value indicating whether the intro screen has been displayed to the user. This value might influence the user's initial experience and subsequent interactions with the application.

The reference to Line 191: ONYXKEYS.NVP_INTRO_SELECTED pinpoints the exact location within the module where the Onyx.connect call needs to be removed or refactored. This level of detail helps developers quickly locate the relevant code and understand its purpose. Knowing the specific key and its usage context is essential for planning the refactoring steps and ensuring that the replacement mechanism correctly handles the data previously managed by Onyx.connect.

The Test-Driven Development (TDD) Approach

This refactoring process strictly adheres to the principles of Test-Driven Development (TDD). TDD is a software development methodology where tests are written before the code itself. This approach helps to ensure that the code behaves as expected and that any changes made during refactoring do not introduce unintended side effects. The TDD cycle involves the following steps:

  1. Write a Unit Test: Before making any changes to the code, a unit test is created to define the expected behavior of the function or module being refactored. This test should fail initially, as the functionality to satisfy the test has not yet been implemented.
  2. Refactor the Methods: The next step involves modifying the code to remove the Onyx.connect call and replace it with an alternative data fetching mechanism. This might involve using hooks, context, or other state management techniques.
  3. Ensure the Unit Test Still Runs: After refactoring, the unit test is executed again. If the refactoring was successful, the test should now pass, indicating that the code behaves as expected.
  4. Reinforce Testing with Functional and QA Tests: To further ensure the reliability of the changes, functional tests and QA tests are added. Functional tests verify that the feature works correctly from a user perspective, while QA tests involve manual testing by quality assurance engineers to identify any potential issues.

By following this TDD approach, developers can confidently refactor code while minimizing the risk of introducing bugs or breaking existing functionality.

Step 1: Creating a Unit Test

The first step in the TDD process is to create a unit test for the method or component that uses Onyx.connect with the ONYXKEYS.NVP_INTRO_SELECTED key. This unit test should assert the expected behavior of the code before any refactoring takes place. For example, the test might check that the correct value is returned when accessing the NVP_INTRO_SELECTED data, or that a specific function is called when the value changes.

The unit test should be specific and focused, testing only the functionality related to Onyx.connect and the NVP_INTRO_SELECTED key. This helps to isolate any issues that might arise during refactoring and makes it easier to debug the code.

Step 2: Refactoring the Methods

Once the unit test is in place, the next step is to refactor the code to remove the Onyx.connect call. This might involve replacing it with a different data fetching mechanism, such as React hooks (useState, useContext), a global state management library (like Redux or Zustand), or a custom solution tailored to the application's needs.

The specific approach used for refactoring will depend on the context of the code and the overall architecture of the application. However, the goal is to replace Onyx.connect with a solution that is more efficient, maintainable, and scalable.

Step 3: Ensuring the Unit Test Still Runs

After refactoring the code, it is crucial to run the unit test again to ensure that the changes have not introduced any regressions. If the unit test passes, this indicates that the code still behaves as expected and that the refactoring was successful.

If the unit test fails, this means that the refactoring has introduced a bug or broken existing functionality. In this case, the developer needs to debug the code and make the necessary adjustments until the unit test passes.

Step 4: Reinforcing Testing with Functional and QA Tests

While unit tests are essential for verifying the correctness of individual components, they do not guarantee that the application works correctly as a whole. To ensure the reliability of the changes, it is important to supplement unit tests with functional tests and QA tests.

Functional tests verify that the feature works correctly from a user perspective. For example, a functional test might simulate a user interacting with the application and check that the NVP_INTRO_SELECTED value is updated correctly when the intro screen is displayed or dismissed.

QA tests involve manual testing by quality assurance engineers. QA testers will explore the application and try to identify any potential issues that might not be caught by automated tests. This might involve testing edge cases, performance issues, or usability problems.

Step 5: Decreasing Allowable ESLint Warnings

As part of the deprecation effort, it's essential to track and reduce the number of Onyx.connect usages across the codebase. The project maintains a count of allowable ESLint warnings related to Onyx.connect. After successfully removing an instance of Onyx.connect, the number of allowable warnings should be decreased to reflect the progress. This ensures that the deprecation effort is systematically tracked and that the codebase is gradually migrated away from Onyx.connect.

The provided link to package.json (https://github.com/Expensify/App/blob/e7b5ac9401e2ae9b5c2c70ec513e8de6f5279d7d/package.json#L48) points to the specific line in the project's package.json file where the allowable warning count is defined. Updating this value ensures that the ESLint configuration accurately reflects the current state of Onyx.connect usage.

Potential Challenges and Considerations

Refactoring code that uses Onyx.connect can present several challenges. Some potential issues to consider include:

  • Data Consistency: Ensuring that the replacement data fetching mechanism maintains data consistency is crucial. If the NVP_INTRO_SELECTED value is not updated correctly, this could lead to unexpected behavior in the application.
  • Performance: The replacement data fetching mechanism should be performant and not introduce any performance regressions. This is especially important for frequently accessed data.
  • Complexity: Refactoring code can sometimes introduce new complexity. It is important to ensure that the replacement solution is as simple and maintainable as possible.
  • Testing Thoroughness: Adequate testing is critical to ensuring that the refactoring is successful. Unit tests, functional tests, and QA tests should all be used to verify the correctness of the changes.

Conclusion

Removing Onyx.connect() for the key ONYXKEYS.NVP_INTRO_SELECTED in src/libs/SubscriptionUtils.ts is a crucial step in deprecating Onyx.connect and modernizing the Expensify application. By following a test-driven development approach and addressing potential challenges proactively, developers can confidently refactor code while minimizing the risk of introducing bugs or breaking existing functionality. The emphasis on thorough testing, including unit, functional, and QA tests, ensures the reliability and maintainability of the codebase. This systematic approach contributes to the long-term health and scalability of the Expensify application.

This article has provided a comprehensive guide to the process, highlighting the importance of understanding the context, identifying the target, and adhering to TDD principles. By following these guidelines, developers can successfully remove Onyx.connect and contribute to the overall improvement of the Expensify application's architecture.