add changelog entry

Author: teoxoy

CHANGELOG.md

@@ -42,6 +42,26 @@ Bottom level categories:
 
 ## Unreleased
 
+### Major changes
+
+#### Optional vertex buffer slots
+
+This allows gaps in `VertexState`'s `buffers` and adds support for unbinding vertex buffers, bringing us in compliance with the WebGPU spec. As a result of this `VertexState`'s `buffers` field now has type of `&[Option<VertexBufferLayout>]`. To migrate wrap vertex buffer layouts in `Some`:
+
+```diff
+  let vertex_state = wgpu::VertexState {
+      module: &vs_module,
+      entry_point: Some("vs_main"),
+      compilation_options: wgpu::PipelineCompilationOptions::default(),
+      buffers: &[
+-         &vertex_buffer_layout
++         Some(&vertex_buffer_layout)
+      ],
+  };
+```
+
+By @teoxoy in [#9351](https://github.com/gfx-rs/wgpu/pull/9351).
+
 ### Added/New Features
 
 #### General

wgpu/src/backend/webgpu.rs

@@ -2180,8 +2180,8 @@ impl dispatch::DeviceInterface for WebDevice {
             .vertex
             .buffers
             .iter()
-            .map(|vbuf| {
-                vbuf.as_ref().map(|vbuf| {
+            .map(|vbuf| match vbuf {
+                Some(vbuf) => {
                     let mapped_attributes = vbuf
                         .attributes
                         .iter()
@@ -2199,8 +2199,9 @@ impl dispatch::DeviceInterface for WebDevice {
                         &mapped_attributes,
                     );
                     mapped_vbuf.set_step_mode(map_vertex_step_mode(vbuf.step_mode));
-                    mapped_vbuf
-                })
+                    wasm_bindgen::JsValue::from(mapped_vbuf)
+                }
+                None => wasm_bindgen::JsValue::NULL,
             })
             .collect::<js_sys::Array>();