Command encoder released without endEncoding

[kvark]

Description
Still getting these errors from Gecko sometimes.

Repro steps
None

Expected vs observed behavior
No Metal validation error is expected

Extra materials
https://bugzilla.mozilla.org/show_bug.cgi?id=1729648#c5

[kpreid]

Here's a repro (of at least one way to get this error; I don't know if Gecko is hitting the same case I am, but I'm mentioning this here to hopefully avoid filing duplicate issues):

0. At wgpu commit 0b61a19
1. Take wgpu/examples/hello-triangle, perhaps.
2. Comment out rpass.set_pipeline(&render_pipeline); — i.e. submit a render pass without having specified the pipeline.

The results I get are:

[2022-04-23T22:20:09Z ERROR wgpu::backend::direct] Handling wgpu errors as fatal by default
thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In a RenderPass
      note: encoder = `<CommandBuffer-(0, 1, Metal)>`
    In a draw command, indexed:false indirect:false
    render pipeline must be set

', wgpu/src/backend/direct.rs:2286:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
-[_MTLCommandEncoder dealloc]:131: failed assertion `Command encoder released without endEncoding'
Abort trap: 6

By inserting logging, the assertion appears to occur while Rust is unwinding, unsurprisingly when wgpu_hal::metal::CommandState is dropping its render field of type Option<mtl::RenderCommandEncoder>. Experimentally adding the code

impl Drop for CommandEncoder {
    fn drop(&mut self) {
        if let Some(render) = self.state.render.take() {
            render.end_encoding();
        }
    }
}

to wgpu_hal::metal::CommandEncoder causes the program to finish panicking and exit without the assertion, but I haven't studied the code architecture and certainly can't say this is a correct general fix. (Presumably it at least should treat blit and compute similarly?)

[RayMarch]

i encountered a very similar error today which might be related:

• i created a render pipeline with a PrimitiveTopology::TriangleStrip and strip_index_format: Some(IndexFormat::Uint32).
• created a render pass, bound the pipeline
• bound an index buffer with mismatching index format IndexFormat::Uint16
• called render_pass.draw_indexed(...)
• drop the render pass

and i got this MTL error on top of wgpu's validation error

[2022-06-03T21:38:39Z ERROR wgpu::backend::direct] Handling wgpu errors as fatal by default
thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In a RenderPass
      note: encoder = `render encoder`
    In a draw command, indexed:true indirect:false
      note: render pipeline = `<RenderPipeline-(0, 1, Metal)>`
    pipeline index format (Uint32) and buffer index format (Uint16) do not match

', /Users/user/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.12.0/src/backend/direct.rs:2273:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
-[_MTLCommandEncoder dealloc]:70: failed assertion `Command encoder released without endEncoding'

[jimblandy]

We believe this was fixed by #4023.