Fix Game Built For Old Version Not Running With New Python Stubs

Hey guys! Today, we're diving into a common issue that arises when working with retro game development platforms like TIC-80 and dealing with Python stubs. Specifically, we're looking at a situation where a game built for an older version of TIC-80 throws an error when run with newer Python stubs. Let's break down the problem, the solution, and how to potentially avoid it in the future.

Understanding the Issue

The core problem revolves around compatibility between different versions of Python stubs and how they interact with game code. In the context of TIC-80, a fantasy console, Python is often used as the scripting language for creating games. Stubs, in this case, are essentially interface definitions that help the code editor understand the available functions and their expected input types.

When new stubs are introduced, they might enforce stricter type checking or change the expected data types for certain functions. This can lead to legacy code, which worked perfectly fine with older stubs, suddenly throwing type errors. This is exactly what happened with the game "o moku e mun," as reported by a developer who encountered a TypeError: expected 'int', got 'float' after updating to the latest TIC-80 version with new Python stubs.

In the given example, the error occurred within the tile_has_flag function, which ultimately calls mget to retrieve tile data. The issue is that mget expects integer coordinates (tx, ty), but in the older code, these coordinates might have been implicitly or explicitly treated as floats. The new stubs, with their stricter type checking, flagged this discrepancy, causing the error. The original code snippet:

 return fget(mget(tx,ty),f)

was fixed by explicitly converting tx and ty to integers using int(tx) and int(ty):

 return fget(mget(int(tx),int(ty)),f)

This highlights a crucial aspect of software development: the importance of explicit type handling. While Python is dynamically typed, meaning you don't always need to declare the type of a variable, being mindful of data types and performing necessary conversions can prevent unexpected errors, especially when dealing with evolving libraries and stubs.

Deep Dive into Type Errors and Python

To further understand this issue, let's delve a bit deeper into type errors in Python. Python, while dynamically typed, is strongly typed, meaning that the interpreter enforces type rules at runtime. This means that you can't perform operations on incompatible types (e.g., adding a string to an integer) without explicit conversion. In our case, the mget function in the TIC-80 API is designed to work with integer coordinates because tilemaps are essentially grids of integer-indexed tiles. When a float value is passed, the function throws a TypeError because it's not designed to handle non-integer indices. This kind of error is crucial to catch because it prevents the program from accessing memory locations that it shouldn't, which could lead to crashes or undefined behavior.

The evolution of Python stubs in environments like TIC-80 aims to enhance code quality and prevent these types of runtime errors. By enforcing stricter type checking, the stubs act as a safety net, catching potential issues during development rather than when the game is running. This approach aligns with the best practices in software engineering, which emphasize writing robust, error-free code.

However, as we've seen, this increased rigor can sometimes break legacy code that relied on implicit type conversions or loose type handling. This is a common trade-off in software development: balancing backward compatibility with the benefits of newer, more robust systems. The challenge then becomes how to mitigate these breakages while still leveraging the advantages of updated tools and libraries.

The Solution and a Broader Perspective

The immediate solution, as demonstrated, is to explicitly convert the float values to integers before passing them to the mget function. This resolves the type mismatch and allows the game to run. However, this fix raises a more significant question: How can we prevent similar issues from occurring in the future, especially when dealing with a potentially large codebase or multiple legacy projects?

One approach is to adopt a more proactive coding style that emphasizes explicit type handling from the outset. This includes being mindful of data types when writing code and performing necessary conversions early on. For example, if a coordinate is calculated as a float, it's a good practice to immediately convert it to an integer if it's going to be used as a tile index. This reduces the risk of implicit type conversions causing errors later. Furthermore, thorough testing is crucial. Regularly running your game with the latest stubs and tools can help catch these types of issues early in the development cycle. Automated testing, if feasible, can further streamline this process.

Another strategy is to carefully manage dependencies and be aware of changes in the libraries and tools you're using. When updating to a new version of TIC-80 or other game development environments, it's always a good idea to review the release notes and changelogs for any breaking changes that might affect your projects. This allows you to anticipate potential issues and plan accordingly.

Linting and Disabling It (with Caution)

The original poster also raised an interesting point about disabling linting when running a cart. Linting is a process of analyzing code for potential errors, stylistic issues, and deviations from coding standards. While linting is generally a good thing, as it helps catch bugs and improve code quality, there might be situations where you want to temporarily disable it, especially when dealing with legacy code that might not conform to the latest linting rules.

However, disabling linting should be approached with caution. While it might provide a temporary workaround for compatibility issues, it also means that you're potentially bypassing valuable error detection mechanisms. A better approach is to address the underlying issues in the code, such as the type mismatches we discussed earlier, rather than simply suppressing the warnings.

In the context of TIC-80, there might be options within the development environment to configure linting rules or selectively disable certain checks. However, the specific mechanisms for doing this would depend on the version of TIC-80 and the tools being used. If you're considering disabling linting, it's always a good idea to document why you're doing it and to re-enable it as soon as possible after addressing the underlying issues.

Preventing Future Breakage

To really future-proof your TIC-80 projects and minimize the chances of encountering similar issues down the line, there are several best practices you can incorporate into your workflow. One of the most effective is to write modular code. By breaking your game logic into smaller, self-contained functions and modules, you make it easier to isolate and fix issues when they arise. This also makes your code more readable and maintainable in the long run.

Another key principle is to avoid relying on implicit behavior. This means being explicit about your intentions in your code, rather than assuming that the system will do what you expect. For example, if you need an integer, explicitly convert the value to an integer rather than relying on implicit conversion. This not only makes your code more robust but also easier to understand for other developers (or even your future self!).

Embracing Type Hints in Python

One of the most powerful tools for preventing type-related errors in Python is the use of type hints. Type hints, introduced in Python 3.5, allow you to specify the expected data types for function arguments and return values. While Python remains a dynamically typed language, type hints provide valuable information to static analysis tools (like linters and type checkers) that can catch type errors before you even run your code.

For example, in our tile_has_flag function, we could add type hints like this:

def tile_has_flag(tx: int, ty: int, f: int) -> bool:
 return fget(mget(tx, ty), f)

This tells the type checker that tx, ty, and f are expected to be integers, and that the function should return a boolean value. If we were to accidentally pass a float value to tx or ty, the type checker would flag it as an error.

While adding type hints might seem like extra work upfront, it can save you a significant amount of time and effort in the long run by preventing runtime errors and making your code more maintainable. Furthermore, type hints make your code easier to understand for others, as they clearly document the expected data types. They're a fantastic way to communicate your intentions and ensure that your code behaves as expected.

Conclusion

This issue with the older game not running on newer Python stubs highlights the challenges of maintaining compatibility in a constantly evolving software ecosystem. The key takeaways are to be mindful of data types, handle type conversions explicitly, test your code regularly, and embrace tools like type hints to catch errors early. By adopting these practices, you can minimize the risk of breakage and ensure that your TIC-80 games (and other Python projects) remain robust and reliable. Remember guys, by understanding the root cause of the error and taking proactive steps, we can create awesome games without pulling our hair out over unexpected issues! We've explored how newer Python stubs can cause issues with legacy code due to stricter type checking, especially with functions like mget in TIC-80. We've also covered the immediate fix of explicitly converting floats to integers, and the broader strategies of proactive coding, managing dependencies, and the cautious use of disabling linting. To avoid future issues, consider writing modular code, avoiding implicit behavior, and embracing Python's type hints. By staying aware and adopting these practices, you can keep your TIC-80 game development smooth and your games running flawlessly. Happy coding!