Eliminate `todo!()` Macros To Prevent Aria Crashes
Hey everyone,
It's crucial that we address the remaining todo!() macros in our codebase before launch. These macros act as explicit crash triggers, and we need to resolve them to ensure Aria's stability. Let's dive into the specifics and get these fixed!
The Problem: Lingering todo!() Macros
Currently, there are two instances of todo!() that need our attention:
RuntimeValue::identity: RuntimeValue::Type(_) => todo!(),ListImp::set_at: std::cmp::Ordering::Greater => todo!(),
These aren't just placeholders; they are deterministic points where Aria will crash if the corresponding code paths are executed. Let's break down why this is a problem and how to tackle it.
Why todo!() is a No-Go for Launch
The todo!() macro in Rust is essentially a way to mark code that's not yet implemented. When the program encounters a todo!(), it panics, causing the program to halt execution. This is incredibly useful during development to highlight areas that still need work. However, in a production environment, these panics are unacceptable. They lead to unexpected crashes and a poor user experience.
Imagine a user trying to perform a seemingly simple operation, like checking the type of a value or setting an element in a list, and suddenly, the entire application crashes. That's the reality if we leave these todo!() macros in place. It's not just about preventing crashes; it's about ensuring the reliability and trustworthiness of our platform. Users need to know that Aria will behave predictably and won't randomly fail on them.
Understanding the Impact
Let's look at the specific examples and understand the scenarios that trigger these todo!() macros.
1. RuntimeValue::identity
The identity function in RuntimeValue is supposed to return the identity value for a given type. However, the current implementation has a todo!() for the RuntimeValue::Type(_) case. This means that if the code tries to get the identity value of a Type, Aria will crash. The provided example demonstrates this:
〉identity(typeof(1));
thread 'main' panicked at vm-lib/src/runtime_value/mod.rs:112:38:
not yet implemented
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
This shows that when we try to get the identity of a type (in this case, the type of 1), the program panics because the todo!() is hit. We need to implement the correct behavior for this case to prevent this crash.
2. ListImp::set_at
The set_at function in ListImp is responsible for setting the value at a specific index in a list. The todo!() is triggered when the index is greater than the current length of the list (std::cmp::Ordering::Greater). This means that if you try to set a value at an index that's out of bounds, Aria will crash. The example illustrates this:
〉[][10] = 1;
thread 'main' panicked at vm-lib/src/runtime_value/list.rs:50:44:
not yet implemented
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Here, we're trying to set the value 1 at index 10 of an empty list. Since the index is out of bounds, the todo!() is triggered, and the program panics. We need to handle this out-of-bounds scenario gracefully, either by resizing the list or returning an error, instead of crashing.
The Solution: Removing the todo!() Macros
The solution is straightforward: we need to replace these todo!() macros with proper implementations. This involves understanding the intended behavior for each case and writing the necessary code to achieve it.
Implementing RuntimeValue::identity
For the RuntimeValue::identity function, we need to determine what the identity value for a Type should be. This might involve returning a default value for the type, such as 0 for numbers, false for booleans, or an empty string for strings. The exact behavior will depend on the semantics of our language and what makes sense in the context of Aria.
Here's a possible implementation (remember to adjust it based on your specific requirements):
impl RuntimeValue {
fn identity(ty: &Type) -> Self {
match ty {
Type::Number => RuntimeValue::Number(0.0), // Default number value
Type::Boolean => RuntimeValue::Boolean(false), // Default boolean value
Type::String => RuntimeValue::String("".to_string()), // Default string value
// ... other types
Type::Type(_) => {
//Instead of todo, define Type identity
RuntimeValue::String("Type".to_string())
},
}
}
}
In this example, we're returning 0.0 for numbers, false for booleans, and an empty string for strings. The key is to provide a reasonable default value that won't cause unexpected behavior.
Implementing ListImp::set_at
For the ListImp::set_at function, we have a couple of options for handling out-of-bounds indices:
- Resize the list: We can automatically resize the list to accommodate the new index. This is a convenient option for the user, but it might have performance implications if the list is frequently resized.
- Return an error: We can return an error to indicate that the index is out of bounds. This gives the user more control over how to handle the error, but it requires them to explicitly check for errors.
Here's an example of resizing the list:
impl ListImp {
fn set_at(&mut self, index: usize, value: RuntimeValue) {
match index.cmp(&self.values.len()) {
std::cmp::Ordering::Less => {
self.values[index] = value;
}
std::cmp::Ordering::Equal => {
self.values.push(value);
}
std::cmp::Ordering::Greater => {
// Resize the list to accommodate the new index
self.values.resize(index + 1, RuntimeValue::Null); // Or some other default value
self.values[index] = value;
}
}
}
}
In this example, we're using resize to increase the size of the list to index + 1. We're filling the new elements with RuntimeValue::Null, but you can use any default value that makes sense for your application. Alternatively, if you chose to return an error, here's how you can do it:
impl ListImp {
fn set_at(&mut self, index: usize, value: RuntimeValue) -> Result<(), String> {
match index.cmp(&self.values.len()) {
std::cmp::Ordering::Less => {
self.values[index] = value;
Ok(())
}
std::cmp::Ordering::Equal => {
self.values.push(value);
Ok(())
}
std::cmp::Ordering::Greater => {
// Return an error
Err("Index out of bounds".to_string())
}
}
}
}
In this case, we're returning a Result type. If the index is out of bounds, we return an Err with an error message. Otherwise, we return Ok(()) to indicate success. Remember to handle the result properly to avoid the program crashing or misbehaving.
Testing the Fixes
After implementing these changes, it's crucial to test them thoroughly. You can use the examples provided in the original issue to verify that the crashes are no longer happening. Additionally, you should write more comprehensive tests to cover all possible scenarios and edge cases.
For example, you can test RuntimeValue::identity with different types and ensure that it returns the correct identity values. For ListImp::set_at, you can test setting values at various indices, including out-of-bounds indices, and verify that the list is either resized correctly or an appropriate error is returned.
Here are some test cases you can add:
#[test]
fn test_runtime_value_identity() {
assert_eq!(RuntimeValue::identity(&Type::Number), RuntimeValue::Number(0.0));
assert_eq!(RuntimeValue::identity(&Type::Boolean), RuntimeValue::Boolean(false));
// Add more test cases for other types
}
#[test]
fn test_list_imp_set_at() {
let mut list = ListImp::new();
list.set_at(0, RuntimeValue::Number(1.0));
assert_eq!(list.values[0], RuntimeValue::Number(1.0));
// Test resizing the list
list.set_at(5, RuntimeValue::Number(2.0));
assert_eq!(list.values.len(), 6);
assert_eq!(list.values[5], RuntimeValue::Number(2.0));
}
Write as many unit tests to cover your implementations. This is an important step to ensure that your changes are correct and that they don't introduce any new issues.
Conclusion: Let's Get This Done!
Guys, removing these todo!() macros is a critical step in ensuring Aria's stability and reliability. By implementing the correct behavior for RuntimeValue::identity and ListImp::set_at, and by thoroughly testing our changes, we can prevent unexpected crashes and provide a better experience for our users. Let's get these fixes in and make sure Aria is ready for launch!