Include naga parse error in the error chain

[scoopr]

Connections
Probably makes #1424 moot

Description
Wraps the Naga ParseError with NagaParseError that shows the full Naga diagnostic in its Display impl and adding it to the CreateShaderModuleError::Parsing variant, allows for the wgsl diagnostics to be visible in the displayed validation error.

Testing
With modifying examples

[scoopr]

Looks a little something like this

[2021-08-03T20:46:40Z ERROR wgpu::backend::direct] wgpu error: Validation Error

    Caused by:
        In Device::create_shader_module
          note: label = `water`
        Failed to parse a shader

    Shader error:
    error: invalid field accessor `f_WaterScreenPos`
        ┌─ wgsl:215:9
        │
    215 │     out.f_WaterScreenPos = (0.5 * gridpos.xy * (1.0 / gridpos.w)) + vec2<f32>(0.5, 0.5);
        │         ^^^^^^^^^^^^^^^^ invalid accessor




thread 'main' panicked at 'Handling wgpu errors as fatal by default', wgpu/src/backend/direct.rs:2101:5

[kvark]

Nice!

[almarklein]

I'm really grateful for this change, but one issue I'm facing is that newlines are escaped in the result. An example:

λ python examples\geometry_cube.py
Failed to parse WGSL code for Some(""): no definition in scope for identifier: 'atomicExchange'
thread '<unnamed>' panicked at 'Parsing(NagaParseError { shader_source: "\n        [[block]]\n        struct Struct_u_stdinfo {\n            cam_transform: mat4x4<f32>;\n            cam_transform_inv: mat4x4<f32>;\n            projection_transform: mat4x4<f32>;\n            projection_transform_inv: mat4x4<f32>;\n            physical_size: vec2<f32>;\n            logical_size: vec2<f32>;\n        };\n\n        [[group(0), binding(0)]]\n        var u_stdinfo: Struct_u_stdinfo;\n        \n\n        [[block]]\n        struct Struct_u_wobject {\n            world_transform: mat4x4<f32>;\n            id: i32;\n        };\n\n        [[group(0), binding(1)]]\n        var u_wobject: Struct_u_wobject;\n        \n\n        [[block]]\n        struct [... etc.]

Is this intentional or could we change something to fix this? I reckon it should be a minor change, but I don't know enough about Rust strings to know what that change should be.

[kvark]

Interesting. This is definitely not what we see. Where does this unwrap happens? It's not in wgpu-core, it must be in wgpu-native itself. Should look like this -

wgpu/wgpu/src/backend/direct.rs

Line 2156 in 0e65b93

fn default_error_handler(err: crate::Error) {

[almarklein]

Would that be where create_shader_module is called? (and in check_error here

[kvark]

Right. It needs to be panic!("{}", error); instead of panic!("{:?}", error);

[almarklein]

Then I get:

λ cargo build
   Compiling wgpu-native v0.6.0 (C:\dev\rust\wgpu-native)
error[E0277]: `E` doesn't implement `std::fmt::Display`
  --> src\lib.rs:53:22
   |
53 |         panic!("{}", error);
   |                      ^^^^^ `E` cannot be formatted with the default formatter
   |
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
   = note: required by `std::fmt::Display::fmt`
   = note: this error originates in the macro `$crate::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider further restricting this bound
   |
51 | pub fn check_error<I, E: std::fmt::Debug + std::fmt::Display>(input: (I, Option<E>)) -> I {
   |                                          ^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: could not compile `wgpu-native`

[kvark]

Could you try E: std::error::Error instead?

[almarklein]

Then I can use panic!("{}", error); but then also the text written is reduced to only the error title (what we had before this pr),

[kvark]

Oh, I see now. In wgpu-rs, between the wgpu-core call and the user error report, there is also this piece happening -

wgpu/wgpu/src/backend/direct.rs

Lines 146 to 169 in 0e65b93

	let error = wgc::error::ContextError {
	string,
	cause: Box::new(cause),
	label: label.unwrap_or_default().to_string(),
	label_key,
	};
	let sink = sink_mutex.lock();
	let mut source_opt: Option<&(dyn Error + 'static)> = Some(&error);
	while let Some(source) = source_opt {
	if let Some(wgc::device::DeviceError::OutOfMemory) =
	source.downcast_ref::<wgc::device::DeviceError>()
	{
	return sink.handle_error(crate::Error::OutOfMemoryError {
	source: Box::new(error),
	});
	}
	source_opt = source.source();
	}
	// Otherwise, it is a validation error
	sink.handle_error(crate::Error::ValidationError {
	description: self.format_error(&error),
	source: Box::new(error),
	});

And that's not a part of wgpu-native atm. Would you mind filing an issue to wgpu-native to follow-up on this?