allow explicit undefined in entity.update

.changeset/forty-tomatoes-rush.md

@@ -0,0 +1,5 @@
+---
+'@verdant-web/store': patch
+---
+
+Allow explicit undefined values in Entity.update. Ignore them by default.

packages/store/src/entities/Entity.test.ts

@@ -215,4 +215,27 @@ describe('Entity', () => {
 			});
 		});
 	});
+
+	describe('changes', () => {
+		it('can apply partial updates including undefineds', () => {
+			const { entity, initialize } = createTestEntity();
+
+			initialize({
+				id: 'hi',
+				string: 'world',
+				number: 1,
+				nullable: null,
+				nonNullable: { first: { inner: 'foo' } },
+				map: {},
+				list: [20, { inner: 'yay' }],
+			});
+
+			entity.update({
+				string: 'new world',
+				number: undefined,
+			});
+
+			expect(entity.get('string')).toBe('new world');
+		});
+	});
 });

packages/store/src/entities/Entity.ts

@@ -786,7 +786,12 @@ export class Entity<
 		{
 			merge = true,
 			replaceSubObjects = false,
-		}: { replaceSubObjects?: boolean; merge?: boolean } = {},
+			preserveUndefined = false,
+		}: {
+			replaceSubObjects?: boolean;
+			merge?: boolean;
+			preserveUndefined?: boolean;
+		} = {},
 	): void => {
 		if (!merge && this.schema.type !== 'any' && this.schema.type !== 'map') {
 			throw new Error(
@@ -799,6 +804,9 @@ export class Entity<
 			if (this.readonlyKeys.includes(key as any)) {
 				throw new Error(`Cannot set readonly key ${key.toString()}`);
 			}
+			// ignore undefined values unless overridden
+			if (field === undefined && !preserveUndefined) continue;
+
 			const fieldSchema = getChildFieldSchema(this.schema, key);
 			if (fieldSchema) {
 				traverseCollectionFieldsAndApplyDefaults(field, fieldSchema);