Reduce the number of subcases in null_bind_group_layouts

src/common/util/util.ts

@@ -258,6 +258,15 @@ export function mapLazy<T, R>(xs: Iterable<T>, f: (x: T) => R): Iterable<R> {
   };
 }
 
+/** Count the number of elements `x` for which `predicate(x)` is true. */
+export function count<T>(xs: Iterable<T>, predicate: (x: T) => boolean): number {
+  let count = 0;
+  for (const x of xs) {
+    if (predicate(x)) count++;
+  }
+  return count;
+}
+
 const ReorderOrders = {
   forward: true,
   backward: true,

src/webgpu/api/validation/createPipelineLayout.spec.ts

@@ -5,6 +5,7 @@ TODO: review existing tests, write descriptions, and make sure tests are complet
 `;
 
 import { makeTestGroup } from '../../../common/framework/test_group.js';
+import { count } from '../../../common/util/util.js';
 import { bufferBindingTypeInfo, kBufferBindingTypes } from '../../capability_info.js';
 import { GPUConst } from '../../constants.js';
 
@@ -174,41 +175,17 @@ g.test('bind_group_layouts,null_bind_group_layouts')
   )
   .paramsSubcasesOnly(u =>
     u //
-      .combine('bindGroupLayoutCount', [1, 2, 3, 4] as const)
-      .combine('bindGroupLayout0', MaybeNullBindGroupLayoutTypes)
-      .expand('bindGroupLayout1', p =>
-        p.bindGroupLayoutCount > 1 ? MaybeNullBindGroupLayoutTypes : (['Null'] as const)
-      )
-      .expand('bindGroupLayout2', p =>
-        p.bindGroupLayoutCount > 2 ? MaybeNullBindGroupLayoutTypes : (['Null'] as const)
-      )
-      .expand('bindGroupLayout3', p =>
-        p.bindGroupLayoutCount > 3 ? MaybeNullBindGroupLayoutTypes : (['Null'] as const)
-      )
-      .filter(p => {
-        // Only test cases where at least one of the bind group layouts is null.
-        const allBGLs = [
-          p.bindGroupLayout0,
-          p.bindGroupLayout1,
-          p.bindGroupLayout2,
-          p.bindGroupLayout3,
-        ];
-        const bgls = allBGLs.slice(0, p.bindGroupLayoutCount);
-        return bgls.includes('Null') || bgls.includes('Undefined');
-      })
+      .combine('_bglCount', [1, 2, 3, 4] as const)
+      .combine('_bgl0', MaybeNullBindGroupLayoutTypes)
+      .expand('_bgl1', p => (p._bglCount > 1 ? MaybeNullBindGroupLayoutTypes : (['Null'] as const)))
+      .expand('_bgl2', p => (p._bglCount > 2 ? MaybeNullBindGroupLayoutTypes : (['Null'] as const)))
+      .expand('_bgl3', p => (p._bglCount > 3 ? MaybeNullBindGroupLayoutTypes : (['Null'] as const)))
+      // Flatten the result down into a single subcase arg which is an array of BGL types.
+      .expand('bindGroupLayouts', p => [[p._bgl0, p._bgl1, p._bgl2, p._bgl3].slice(0, p._bglCount)])
+      // Only test combinations where exactly one of the BGLs is null|undefined|empty.
+      .filter(p => count(p.bindGroupLayouts, x => x !== 'NonEmpty') === 1)
   )
   .fn(t => {
-    const {
-      bindGroupLayoutCount,
-      bindGroupLayout0,
-      bindGroupLayout1,
-      bindGroupLayout2,
-      bindGroupLayout3,
-    } = t.params;
-
-    const emptyBindGroupLayout = t.device.createBindGroupLayout({
-      entries: [],
-    });
     const nonEmptyBindGroupLayout = t.device.createBindGroupLayout({
       entries: [
         {
@@ -219,37 +196,18 @@ g.test('bind_group_layouts,null_bind_group_layouts')
       ],
     });
 
-    const bindGroupLayouts: (GPUBindGroupLayout | null | undefined)[] = [];
-
-    const AddBindGroupLayout = function (
-      bindGroupLayoutType: (typeof MaybeNullBindGroupLayoutTypes)[number]
-    ) {
+    const bindGroupLayouts = t.params.bindGroupLayouts.map(bindGroupLayoutType => {
       switch (bindGroupLayoutType) {
         case 'Null':
-          bindGroupLayouts.push(null);
-          break;
+          return null;
         case 'Undefined':
-          bindGroupLayouts.push(undefined);
-          break;
+          return undefined;
         case 'Empty':
-          bindGroupLayouts.push(emptyBindGroupLayout);
-          break;
+          return t.device.createBindGroupLayout({ entries: [] });
         case 'NonEmpty':
-          bindGroupLayouts.push(nonEmptyBindGroupLayout);
-          break;
+          return nonEmptyBindGroupLayout;
       }
-    };
-
-    AddBindGroupLayout(bindGroupLayout0);
-    if (bindGroupLayoutCount > 1) {
-      AddBindGroupLayout(bindGroupLayout1);
-    }
-    if (bindGroupLayoutCount > 2) {
-      AddBindGroupLayout(bindGroupLayout2);
-    }
-    if (bindGroupLayoutCount > 3) {
-      AddBindGroupLayout(bindGroupLayout3);
-    }
+    });
 
     const kShouldError = false;
     t.expectValidationError(() => {