validation: More detailed on incompatible BGL (#4826)

wgpu-core/src/command/bind.rs

@@ -53,6 +53,79 @@ mod compat {
         fn is_incompatible(&self) -> bool {
             self.expected.is_none() || !self.is_valid()
         }
+
+        // Describe how bind group layouts are incompatible, for validation
+        // error message.
+        fn bgl_diff(&self) -> Vec<String> {
+            let mut diff = Vec::new();
+
+            if let Some(expected_bgl) = self.expected.as_ref() {
+                diff.push(format!(
+                    "Should be compatible with bind group layout with label = `{}`",
+                    expected_bgl.label()
+                ));
+                if let Some(assigned_bgl) = self.assigned.as_ref() {
+                    diff.push(format!(
+                        "Assigned bind group layout with label = `{}`",
+                        assigned_bgl.label()
+                    ));
+                    for (id, e_entry) in &expected_bgl.entries {
+                        if let Some(a_entry) = assigned_bgl.entries.get(id) {
+                            if a_entry.binding != e_entry.binding {
+                                diff.push(format!(
+                                    "Entry {id} binding expected {}, got {}",
+                                    e_entry.binding, a_entry.binding
+                                ));
+                            }
+                            if a_entry.count != e_entry.count {
+                                diff.push(format!(
+                                    "Entry {id} count expected {:?}, got {:?}",
+                                    e_entry.count, a_entry.count
+                                ));
+                            }
+                            if a_entry.ty != e_entry.ty {
+                                diff.push(format!(
+                                    "Entry {id} type expected {:?}, got {:?}",
+                                    e_entry.ty, a_entry.ty
+                                ));
+                            }
+                            if a_entry.visibility != e_entry.visibility {
+                                diff.push(format!(
+                                    "Entry {id} visibility expected {:?}, got {:?}",
+                                    e_entry.visibility, a_entry.visibility
+                                ));
+                            }
+                        } else {
+                            diff.push(format!("Entry {id} not found in assigned bindgroup layout"))
+                        }
+                    }
+
+                    assigned_bgl.entries.iter().for_each(|(id, _e_entry)| {
+                        if !expected_bgl.entries.contains_key(id) {
+                            diff.push(format!("Entry {id} not found in expected bindgroup layout"))
+                        }
+                    });
+                } else {
+                    diff.push(
+                        "Assigned bindgroup layout is implicit, expected explicit".to_owned(),
+                    );
+                }
+            } else if let Some(assigned_bgl) = self.assigned.as_ref() {
+                diff.push(format!(
+                    "Assigned bind group layout = `{}`",
+                    assigned_bgl.label()
+                ));
+                diff.push(
+                    "Assigned bindgroup layout is not implicit, expected implicit".to_owned(),
+                );
+            }
+
+            if diff.is_empty() {
+                diff.push("But no differences found? (internal error)".to_owned())
+            }
+
+            diff
+        }
     }
 
     #[derive(Debug, Default)]
@@ -121,6 +194,15 @@ mod compat {
                 }
             })
         }
+
+        pub fn bgl_diff(&self) -> Vec<String> {
+            for e in &self.entries {
+                if !e.is_valid() {
+                    return e.bgl_diff();
+                }
+            }
+            vec![String::from("No differences detected? (internal error)")]
+        }
     }
 }
 
@@ -274,6 +356,10 @@ impl<A: HalApi> Binder<A> {
         self.manager.invalid_mask()
     }
 
+    pub(super) fn bgl_diff(&self) -> Vec<String> {
+        self.manager.bgl_diff()
+    }
+
     /// Scan active buffer bindings corresponding to layouts without `min_binding_size` specified.
     pub(super) fn check_late_buffer_bindings(
         &self,

wgpu-core/src/command/compute.rs

@@ -173,12 +173,8 @@ pub struct ComputePassDescriptor<'a> {
 pub enum DispatchError {
     #[error("Compute pipeline must be set")]
     MissingPipeline,
-    #[error("The pipeline layout, associated with the current compute pipeline, contains a bind group layout at index {index} which is incompatible with the bind group layout associated with the bind group at {index}")]
-    IncompatibleBindGroup {
-        index: u32,
-        //expected: BindGroupLayoutId,
-        //provided: Option<(BindGroupLayoutId, BindGroupId)>,
-    },
+    #[error("Incompatible bind group at index {index} in the current compute pipeline")]
+    IncompatibleBindGroup { index: u32, diff: Vec<String> },
     #[error(
         "Each current dispatch group size dimension ({current:?}) must be less or equal to {limit}"
     )]
@@ -245,6 +241,11 @@ impl PrettyError for ComputePassErrorInner {
             Self::InvalidIndirectBuffer(id) => {
                 fmt.buffer_label(&id);
             }
+            Self::Dispatch(DispatchError::IncompatibleBindGroup { ref diff, .. }) => {
+                for d in diff {
+                    fmt.note(&d);
+                }
+            }
             _ => {}
         };
     }
@@ -291,8 +292,11 @@ impl<A: HalApi> State<A> {
         let bind_mask = self.binder.invalid_mask();
         if bind_mask != 0 {
             //let (expected, provided) = self.binder.entries[index as usize].info();
+            let index = bind_mask.trailing_zeros();
+
             return Err(DispatchError::IncompatibleBindGroup {
-                index: bind_mask.trailing_zeros(),
+                index,
+                diff: self.binder.bgl_diff(),
             });
         }
         if self.pipeline.is_none() {

wgpu-core/src/command/draw.rs

@@ -25,12 +25,8 @@ pub enum DrawError {
     MissingVertexBuffer { index: u32 },
     #[error("Index buffer must be set")]
     MissingIndexBuffer,
-    #[error("The pipeline layout, associated with the current render pipeline, contains a bind group layout at index {index} which is incompatible with the bind group layout associated with the bind group at {index}")]
-    IncompatibleBindGroup {
-        index: u32,
-        //expected: BindGroupLayoutId,
-        //provided: Option<(BindGroupLayoutId, BindGroupId)>,
-    },
+    #[error("Incompatible bind group at index {index} in the current render pipeline")]
+    IncompatibleBindGroup { index: u32, diff: Vec<String> },
     #[error("Vertex {last_vertex} extends beyond limit {vertex_limit} imposed by the buffer in slot {slot}. Did you bind the correct `Vertex` step-rate vertex buffer?")]
     VertexBeyondLimit {
         last_vertex: u32,

wgpu-core/src/command/render.rs

@@ -441,6 +441,7 @@ impl<A: HalApi> State<A> {
             //let (expected, provided) = self.binder.entries[index as usize].info();
             return Err(DrawError::IncompatibleBindGroup {
                 index: bind_mask.trailing_zeros(),
+                diff: self.binder.bgl_diff(),
             });
         }
         if self.pipeline.is_none() {
@@ -643,6 +644,11 @@ impl PrettyError for RenderPassErrorInner {
         if let Self::InvalidAttachment(id) = *self {
             fmt.texture_view_label_with_key(&id, "attachment");
         };
+        if let Self::Draw(DrawError::IncompatibleBindGroup { diff, .. }) = self {
+            for d in diff {
+                fmt.note(&d);
+            }
+        };
     }
 }