Account for presentational role conflict resolution in ARIA feature mappings

packages/alfa-aria/src/feature.ts

@@ -10,26 +10,26 @@ import { Scope, Table } from "@siteimprove/alfa-table";
 import { Role } from "./role";
 
 const { hasName, isElement } = Element;
-const { and, equals, test } = Predicate;
+const { and } = Predicate;
 
 export class Feature<N extends string = string> {
   public static of<N extends string>(
     name: N,
-    role: Feature.Aspect<Option<string>> = () => None,
+    role: Feature.Aspect<Option<string>, [Feature.RoleOptions]> = () => None,
     attributes: Feature.Aspect<Map<string, string>> = () => Map.empty(),
     status: Feature.Status = { obsolete: false }
   ): Feature<N> {
     return new Feature(name, role, attributes, status);
   }
 
   private readonly _name: N;
-  private readonly _role: Feature.Aspect<Option<string>>;
+  private readonly _role: Feature.Aspect<Option<string>, [Feature.RoleOptions]>;
   private readonly _attributes: Feature.Aspect<Map<string, string>>;
   private readonly _status: Feature.Status;
 
   private constructor(
     name: N,
-    role: Feature.Aspect<Option<string>>,
+    role: Feature.Aspect<Option<string>, [Feature.RoleOptions]>,
     attributes: Feature.Aspect<Map<string, string>>,
     status: Feature.Status
   ) {
@@ -43,7 +43,7 @@ export class Feature<N extends string = string> {
     return this._name;
   }
 
-  public get role(): Feature.Aspect<Option<string>> {
+  public get role(): Feature.Aspect<Option<string>, [Feature.RoleOptions]> {
     return this._role;
   }
 
@@ -57,12 +57,23 @@ export class Feature<N extends string = string> {
 }
 
 export namespace Feature {
-  export type Aspect<T> = Mapper<Element, T>;
+  export type Aspect<T, A extends Array<unknown> = []> = Mapper<
+    Element,
+    T,
+    A
+  >;
 
   export interface Status {
     readonly obsolete: boolean;
   }
 
+  export interface RoleOptions {
+    /**
+     * @internal
+     */
+    readonly allowPresentational?: boolean;
+  }
+
   const features = Cache.empty<Namespace, Cache<string, Feature>>();
 
   export function register<N extends string>(
@@ -298,9 +309,9 @@ Feature.register(
 
 Feature.register(
   Namespace.HTML,
-  Feature.of("img", (element) =>
+  Feature.of("img", (element, { allowPresentational = true }) =>
     Option.of(
-      element.attribute("alt").some((alt) => alt.value === "")
+      allowPresentational && element.attribute("alt").some((alt) => alt.value === "")
         ? "presentation"
         : "img"
     )

packages/alfa-aria/src/node.ts

@@ -240,7 +240,10 @@ export namespace Node {
                 role.some(isPresentational) &&
                 !isAllowedPresentational(node)
               ) {
-                return Role.from(node, { explicit: false });
+                return Role.from(node, {
+                  explicit: false,
+                  allowPresentational: false,
+                });
               }
 
               return Branched.of(role);

packages/alfa-aria/src/role.ts

@@ -268,7 +268,11 @@ export namespace Role {
                   const feature = Feature.lookup(namespace, element.name);
 
                   return feature.flatMap((feature) =>
-                    feature.role(element).flatMap(Role.lookup)
+                    feature
+                      .role(element, {
+                        allowPresentational: options.allowPresentational,
+                      })
+                      .flatMap(Role.lookup)
                   );
                 });
               }
@@ -280,7 +284,7 @@ export namespace Role {
   }
 
   export namespace from {
-    export interface Options {
+    export interface Options extends Feature.RoleOptions {
       readonly explicit?: boolean;
       readonly implicit?: boolean;
     }