Fix a couple of CSS feature bugs

.changeset/pretty-scissors-explode.md

@@ -0,0 +1,5 @@
+---
+"@siteimprove/alfa-device": patch
+---
+
+**Fixed:** Values of undefined user preferences are now correctly set to their default.

.changeset/short-bees-behave.md

@@ -0,0 +1,5 @@
+---
+"@siteimprove/alfa-css-feature": patch
+---
+
+**Fixed:** Matching of user-preferences in the boolean context now correctly handles `none` defaults.

packages/alfa-css-feature/src/media/feature/discrete.ts

@@ -1,5 +1,5 @@
 import { Keyword, type Parser as CSSParser } from "@siteimprove/alfa-css";
-import type { Device} from "@siteimprove/alfa-device";
+import type { Device } from "@siteimprove/alfa-device";
 import { Preference } from "@siteimprove/alfa-device";
 import { None, Option } from "@siteimprove/alfa-option";
 
@@ -41,7 +41,7 @@ export namespace Discrete {
 
         return this._value
           .map((value) => value.matches(Keyword.of(deviceValue)))
-          .getOr(deviceValue !== booleanFalse ?? "none");
+          .getOr(deviceValue !== (booleanFalse ?? "none"));
       }
 
       private static _from(value: Option<Value<Keyword<K>>>): Discrete {

packages/alfa-css-feature/test/media.spec.ts

@@ -1,7 +1,12 @@
 import { test } from "@siteimprove/alfa-test";
 
 import { Lexer } from "@siteimprove/alfa-css";
-import { Device, Viewport, Display } from "@siteimprove/alfa-device";
+import {
+  Device,
+  Display,
+  Preference,
+  Viewport,
+} from "@siteimprove/alfa-device";
 
 import { Feature } from "../dist/index.js";
 
@@ -460,7 +465,7 @@ test("#matches() matches ranges", (t) => {
   t.deepEqual(isGoldylocks.matches(largeLandscape), false);
 });
 
-test("#matches correctly behave at boundaries", (t) => {
+test("#matches() correctly behave at boundaries", (t) => {
   // Inclusive bound is matched inclusively
   const isLarge = parse(`(width >= ${width}px)`).getUnsafe();
   // Exclusive bound is matched exclusively
@@ -472,3 +477,19 @@ test("#matches correctly behave at boundaries", (t) => {
   t.deepEqual(isSmall.matches(largeLandscape), false);
   t.deepEqual(isLargeToo.matches(largeLandscape), true);
 });
+
+test("#matches() matches boolean prefers-reduced-motion", (t) => {
+  const prefersReducedMotion = parse("(prefers-reduced-motion)").getUnsafe();
+
+  t.deepEqual(prefersReducedMotion.matches(smallPortrait), false);
+
+  const withReducedMotion = Device.of(
+    Device.Type.Screen,
+    Viewport.of(200, 400, Viewport.Orientation.Portrait),
+    Display.of(300),
+    undefined,
+    [Preference.of("prefers-reduced-motion", "reduce")],
+  );
+
+  t.deepEqual(prefersReducedMotion.matches(withReducedMotion), true);
+});

packages/alfa-device/src/device.ts

@@ -84,7 +84,9 @@ export class Device implements Equatable, Hashable, Serializable {
   public preference<N extends Preference.Name>(name: N): Preference<N> {
     return this._preferences
       .get(name)
-      .getOrElse(() => Preference.unset(name)) as Preference<N>;
+      .getOrElse(() =>
+        Preference.of(name, Preference.unset(name)),
+      ) as Preference<N>;
   }
 
   public equals(value: unknown): value is this {