WIP: feat: only require depth config. for fmts. w/ depth

TODO: Ensure that the following changes and discussion get represented
in code:

- https://github.com/gpuweb/gpuweb/pull/4318/files
- gpuweb/gpuweb#3905
- https://github.com/gpuweb/gpuweb/pull/3849/files#r1122411287

wgpu-core/src/device/resource.rs

@@ -3146,8 +3146,23 @@ impl Device {
                 }
 
                 let aspect = hal::FormatAspects::from(ds.format);
-                if ds.is_depth_enabled() && !aspect.contains(hal::FormatAspects::DEPTH) {
-                    break 'error Some(pipeline::DepthStencilStateError::FormatNotDepth(ds.format));
+                match (
+                    aspect.contains(hal::FormatAspects::DEPTH),
+                    ds.depth_write_enabled.zip(ds.depth_compare),
+                ) {
+                    (true, Some(_)) | (false, None) => (),
+                    (true, None) => {
+                        break 'error Some(pipeline::DepthStencilStateError::DepthOpsNotSpecified {
+                            format: ds.format,
+                            depth_write_enabled: ds.depth_write_enabled,
+                            depth_compare: ds.depth_compare,
+                        })
+                    }
+                    (false, Some(_)) => {
+                        break 'error Some(pipeline::DepthStencilStateError::FormatNotDepth(
+                            ds.format,
+                        ))
+                    }
                 }
                 if ds.stencil.is_enabled() && !aspect.contains(hal::FormatAspects::STENCIL) {
                     break 'error Some(pipeline::DepthStencilStateError::FormatNotStencil(

wgpu-types/src/lib.rs

@@ -4884,10 +4884,12 @@ pub struct DepthStencilState {
     ///
     /// [CEbrp]: ../wgpu/struct.CommandEncoder.html#method.begin_render_pass
     pub format: TextureFormat,
-    /// If disabled, depth will not be written to.
-    pub depth_write_enabled: bool,
-    /// Comparison function used to compare depth values in the depth test.
-    pub depth_compare: CompareFunction,
+    /// If disabled, depth will not be written to. Must be specified if `format` has a depth
+    /// component.
+    pub depth_write_enabled: Option<bool>,
+    /// Comparison function used to compare depth values in the depth test. Must be specified if
+    /// `format` has a depth component.
+    pub depth_compare: Option<CompareFunction>,
     /// Stencil state.
     #[cfg_attr(feature = "serde", serde(default))]
     pub stencil: StencilState,
@@ -4900,13 +4902,15 @@ impl DepthStencilState {
     /// Returns true if the depth testing is enabled.
     #[must_use]
     pub fn is_depth_enabled(&self) -> bool {
-        self.depth_compare != CompareFunction::Always || self.depth_write_enabled
+        self.depth_compare
+            .map_or(false, |dc| dc != CompareFunction::Always)
+            || self.depth_write_enabled
     }
 
     /// Returns true if the state doesn't mutate the depth buffer.
     #[must_use]
     pub fn is_depth_read_only(&self) -> bool {
-        !self.depth_write_enabled
+        self.depth_write_enabled.map_or(false, |enabled| !enabled)
     }
 
     /// Returns true if the state doesn't mutate the stencil.