Shader compilation errors are cryptic

[luke-biel]

What problem does this solve or what need does it fill?

During wgsl shader compilation errors that bevy emits are only partial. Compare:

2022-01-24T15:17:42.140124Z ERROR bevy_render::render_resource::pipeline_cache: failed to process shader: 
error: 

to naga equivalent:

error:

Entry point vertex at Vertex is invalid:
	Argument 0 varying error
	Entry point arguments and return values must all have bindings

when missing [[builtin(vertex_index)]] in fn vertex(vertex_index: u32) -> VertexOutput {

or

2022-01-24T15:24:32.360440Z ERROR bevy_render::render_resource::pipeline_cache: failed to process shader: 
error: 
  ┌─ wgsl:8:9
  │
8 │     if (vertex_index == 0) {
  │         ^^^^^^^^^^^^^^^^^ naga::Expression [4]

vs naga:

error:
  ┌─ static_grid_copy.wgsl:8:9
  │
8 │     if (vertex_index == 0) {
  │         ^^^^^^^^^^^^^^^^^ naga::Expression [4]

Entry point vertex at Vertex is invalid:
	Expression [4] is invalid
	Operation Equal can't work with [1] and [3]

when trying to compare u32 vs signed value.

What solution would you like?

I'd like last part provided by naga that describes what's happening to be attached along with rest of the error.

Additional context

https://github.com/bevyengine/bevy/blob/main/crates/bevy_render/src/render_resource/pipeline_cache.rs#L463
looks identical to
https://github.com/gfx-rs/naga/blob/master/cli/src/main.rs#L500

In naga there's second function https://github.com/gfx-rs/naga/blob/master/cli/src/main.rs#L150 that prints remainder of the error. Simply copy pasting print_err body expanded my error to:

2022-01-24T15:24:32.342290Z ERROR naga::valid::expression: Right: Constant([1]) of type Scalar { kind: Sint, width: 4 }    
Entry point vertex at Vertex is invalid: 
	Expression [4] is invalid
	Operation Equal can't work with [1] and [3]
2022-01-24T15:24:32.360440Z ERROR bevy_render::render_resource::pipeline_cache: failed to process shader: 
error: 
  ┌─ wgsl:8:9
  │
8 │     if (vertex_index == 0) {
  │         ^^^^^^^^^^^^^^^^^ naga::Expression [4]

which is sufficient.

I can provide a PR if this is acceptable solution.

[jakobhellermann]

There's a PR that includes the causes in the error message: #3724.

[luke-biel]

Missed that. Great news then :)

[mockersf]

#3724 has been merged, is it ok for you now?
would #3675 also improve error reporting?

[luke-biel]

In this issue I focused purely on #3724. #3675 isn't directly connected to problems I had so I'm gonna close the issue.

[ErichDonGubler]

In case anybody still thinks that errors are cryptic, like we on the Firefox team do, we're planning on doing some work to make diagnostics nicer: gfx-rs/wgpu#4494