bevy/crates/bevy_render
Chris Russell ac04ec0075 Improve error message for missing resources (#18593)
# Objective

Fixes #18515 

After the recent changes to system param validation, the panic message
for a missing resource is currently:

```
Encountered an error in system `missing_resource_error::res_system`: SystemParamValidationError { skipped: false }
```

Add the parameter type name and a descriptive message, improving the
panic message to:

```
Encountered an error in system `missing_resource_error::res_system`: SystemParamValidationError { skipped: false, message: "Resource does not exist", param: "bevy_ecs::change_detection::Res<missing_resource_error::MissingResource>" }
```

## Solution

Add fields to `SystemParamValidationError` for error context. Include
the `type_name` of the param and a message.

Store them as `Cow<'static, str>` and only format them into a friendly
string in the `Display` impl. This lets us create errors using a
`&'static str` with no allocation or formatting, while still supporting
runtime `String` values if necessary.

Add a unit test that verifies the panic message.

## Future Work

If we change the default error handling to use `Display` instead of
`Debug`, and to use `ShortName` for the system name, the panic message
could be further improved to:

```
Encountered an error in system `res_system`: Parameter `Res<MissingResource>` failed validation: Resource does not exist
```

However, `BevyError` currently includes the backtrace in `Debug` but not
`Display`, and I didn't want to try to change that in this PR.
2025-03-30 10:21:20 +02:00
..
macros Release 0.16.0-rc.2 2025-03-26 19:18:20 +01:00
src Improve error message for missing resources (#18593) 2025-03-30 10:21:20 +02:00
Cargo.toml Tracy GPU support (#18490) 2025-03-28 23:33:00 +01:00
LICENSE-APACHE Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
LICENSE-MIT Cleanup publish process (#17728) 2025-02-09 17:46:19 +00:00
README.md Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00

Bevy Render

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