Code Duplication: A Deep Dive Into Engine Implementations

Hey folks! Ever stumble upon the same code snippets popping up all over the place? Well, in this article, we're diving deep into a situation where we found some serious duplicate code in the engine implementations and safe output jobs within a certain project. This isn't just about a few copy-pasted lines; we're talking about a significant chunk of code that's been replicated across multiple files. Let's break down what we discovered, why it matters, and how we can fix it.

The Lowdown on Code Duplication

So, what's the deal? We analyzed a specific commit (9982620) and found a lot of repeated code across the pkg/workflow/ package. The main offenders? The engine implementations, like Claude, Codex, Copilot, and Custom, along with the builders for safe output jobs. Think of it like this: imagine you're building a house, and you keep using the exact same blueprint for the kitchen, the living room, and the bedroom. That's essentially what's happening here. The estimated amount of duplicated code is between 500 and 700 lines, spread across more than eight different files. That's a lot of wasted effort and a potential headache down the line!

Diving into the Duplication Details

Now, let's get into the nitty-gritty. We identified several recurring patterns of code duplication. Each pattern presents different maintenance issues:

Custom Step Handling in Engine Implementations

This is a high-severity issue because it affects how custom steps are handled by each engine. We saw the same code block repeated across the Claude, Codex, Copilot, and Custom engines. What does this mean? If you need to change how custom steps work, you have to make the same change in multiple places, increasing the risk of errors. This section includes code samples to give you a clearer view.

Safe Outputs Environment Variable Setup

Another high-severity pattern involves setting up environment variables for safe outputs. This code is duplicated across the Codex, Copilot, and Custom engines and in safe output jobs. The environment variables ensure that sensitive data is handled securely. Having the same code in several locations increases the chance of a mistake in one place and not the others, leading to potential security vulnerabilities. This is important for maintaining the integrity of the program. The article provides code examples to illustrate the issue.

Custom Engine Environment Variables Merging

This is a medium-severity issue that relates to merging custom environment variables from the engine configurations. The code is replicated in Codex, Copilot, and Custom engines. As the project grows, there is a chance that the environment variables are not correctly configured and maintained.

Safe Output Job Building Structure

Building safe output jobs is another area of high-severity code duplication. The same structure is used to build jobs for creating issues, pull requests, adding comments, and updating issues. Any changes to the job structure would require modification in multiple files. This increases the chances of inconsistencies and makes it harder to maintain.

NPM Installation Steps

This is a medium-severity pattern, fortunately, this already uses a shared helper function, meaning the DRY (Don't Repeat Yourself) principle is being followed. It's still duplicated across Claude, Codex, and Copilot engines, which means the same code for installing NPM packages is present in multiple places. While it's good to have a helper function, reducing duplication even further would improve code quality.

Configuration Parsing in Safe Outputs

Another medium-severity instance of code duplication involves parsing configurations within safe outputs. This pattern is repeated across multiple files related to creating and updating issues, pull requests, and comments. Keeping this code DRY will help prevent potential errors and make future updates easier.

Max Turns Environment Variable

This is a low-severity issue but still contributes to the overall duplication. The code setting the GITHUB_AW_MAX_TURNS environment variable is duplicated in two engine implementations. Fixing this would contribute to the overall cleanup effort.

Analyzing the Impact

So, what's the big deal with all this duplication? Well, it has several negative effects.

• Maintainability: Changes to the code must be made in multiple places, increasing the risk of inconsistent updates and bugs. Imagine having to update the same logic in a dozen different files every time you need to tweak something. Sounds like a nightmare, right?
• Bug Risk: Duplication makes it much more likely that bugs will slip through the cracks. A fix might be implemented in one place but missed in another, leading to inconsistent behavior across the different engines.
• Code Bloat: As mentioned earlier, hundreds of lines of code are needlessly repeated. This bloats the codebase and makes it harder to understand and navigate.
• Testing Burden: Each duplicated pattern requires separate test coverage. This increases the amount of testing required and the effort to maintain the tests.

Suggested Fixes: Refactoring Recommendations

Fortunately, there are several steps we can take to fix this problem. The key is to refactor the code, which means restructuring it without changing its behavior. Here are some of the recommended refactoring approaches:

1. Extract Engine Environment Variable Setup

The current setup for environment variables is duplicated across several files. By extracting this logic to a dedicated file (e.g., engine_env.go), we can create a single source of truth for environment variable setup. This would make it easier to add new variables consistently and reduce the risk of inconsistencies.

2. Extract Custom Steps Handler

Similarly, extracting the custom steps handler to a separate file (e.g., custom_steps.go) would allow for a single implementation of custom step conversion. This simplifies error handling and ensures consistent step processing across all engines.

3. Create Safe Output Job Builder Base

Building a base structure for safe output job builders would help reduce duplication significantly. This would include building steps, setting environment variables, defining outputs, and building conditions. This approach would result in a consistent job structure and simplify adding new safe output types.

4. Extract Configuration Parser Base

Creating a base class or function for parsing safe output configurations would streamline the parsing process. This would make it easier to extend with new configuration fields and ensure consistent validation and error handling.

5. Consolidate NPM Installation Pattern

This pattern already uses a shared function. The team should review and ensure it is correctly implemented.

Prioritizing the Refactoring Tasks

To get the most bang for our buck, we should prioritize the refactoring tasks. Here's a suggested order:

1. High Priority: Extract Engine Environment Variable Setup (Patterns 2, 3, and 7). This addresses the most frequently duplicated patterns and has the biggest impact on maintainability.
2. High Priority: Extract Custom Steps Handler (Pattern 1). This is a relatively quick win that reduces duplication across all engines.
3. Medium Priority: Create Safe Output Job Builder Base (Pattern 4). This is a larger effort, but it results in a significant reduction in code duplication and improves extensibility.
4. Medium Priority: Extract Configuration Parser Base (Pattern 6). This is moderately complex, but it provides a good return on investment and makes it easier to add new safe output types.

The Path Forward

The final step is to review and validate the duplication findings, prioritize the refactoring tasks based on team capacity, create a detailed plan with a test coverage strategy, and implement the changes incrementally with full test coverage. Make sure there are no behavior changes through integration tests, and update documentation where needed. By following these steps, we can significantly improve the maintainability, reliability, and overall quality of the codebase.

And that's it, guys! We hope this deep dive into code duplication has been helpful. Remember, clean and well-organized code is the key to a happy and productive development process.

For more information about code quality and best practices, check out the Snyk website.