koddsson · koddsson · Mar 13, 2026
diff --git a/generate-act-tests.js b/generate-act-tests.js
@@ -114,7 +114,6 @@ const rulesToIgnore = [
   "97a4e1", // Button has non-empty accessible name - not implemented
   "cae760", // Iframe element has non-empty accessible name - not implemented
   "e086e5", // Form field has non-empty accessible name - not implemented
-  "ffd0e9", // Heading has non-empty accessible name - not implemented
   "m6b1q3", // Menuitem has non-empty accessible name - not implemented
 
   // --- Not implemented - ARIA rules not yet fully supported ---
@@ -137,8 +136,6 @@ const rulesToIgnore = [
 
   // --- Not implemented - page-level and structural rules ---
   "2779a5", // HTML page has non-empty title - not implemented in ACT test format
-  "b5c3f8", // HTML page has lang attribute - not implemented in ACT test format
-  "bf051a", // HTML page lang attribute has valid language tag - not implemented in ACT test format
   "off6ek", // HTML element language subtag matches language - not implemented
   "ucwvc8", // HTML page language subtag matches default language - not implemented
   "c4a8a4", // HTML page title is descriptive - not implemented, requires human judgment
@@ -160,7 +157,6 @@ const rulesToIgnore = [
   "efbfc7", // Text content that changes automatically can be paused, stopped or hidden - not implemented
 
   // --- Unknown or deprecated ACT rules ---
-  "3ea0c8", // Unknown ACT rule - not in current testcases
   "e6952f", // Unknown ACT rule - not in current testcases
 ];
 

diff --git a/rules.json b/rules.json
@@ -273,7 +273,7 @@
         "ACT Rules": "[3ea0c8](https://act-rules.github.io/rules/3ea0c8)"
       },
       {
-        "implemented": "❌",
+        "implemented": "✅",
         "id": "duplicate-id",
         "url": "https://dequeuniversity.com/rules/axe/4.11/duplicate-id?application=RuleDescription",
         "Description": "Ensures every id attribute value is unique",
@@ -323,7 +323,7 @@
         "ACT Rules": "[cae760](https://act-rules.github.io/rules/cae760)"
       },
       {
-        "implemented": "❌",
+        "implemented": "✅",
         "id": "html-has-lang",
         "url": "https://dequeuniversity.com/rules/axe/4.11/html-has-lang?application=RuleDescription",
         "Description": "Ensures every HTML document has a lang attribute",
@@ -333,7 +333,7 @@
         "ACT Rules": "[b5c3f8](https://act-rules.github.io/rules/b5c3f8)"
       },
       {
-        "implemented": "❌",
+        "implemented": "✅",
         "id": "html-lang-valid",
         "url": "https://dequeuniversity.com/rules/axe/4.11/html-lang-valid?application=RuleDescription",
         "Description": "Ensures the lang attribute of the &lt;html&gt; element has a valid value",
@@ -653,7 +653,7 @@
         "ACT Rules": ""
       },
       {
-        "implemented": "❌",
+        "implemented": "✅",
         "id": "empty-heading",
         "url": "https://dequeuniversity.com/rules/axe/4.11/empty-heading?application=RuleDescription",
         "Description": "Ensures headings have discernible text",

diff --git a/src/rules/aria-allowed-attr.ts b/src/rules/aria-allowed-attr.ts
@@ -99,25 +99,33 @@ const implicitRoles: Record<string, string | undefined> = {
 function getInputImplicitRole(element: Element): string | undefined {
   const type = (element.getAttribute("type") || "text").toLowerCase();
   switch (type) {
-    case "checkbox":
+    case "checkbox": {
       return "checkbox";
-    case "radio":
+    }
+    case "radio": {
       return "radio";
-    case "range":
+    }
+    case "range": {
       return "slider";
-    case "number":
+    }
+    case "number": {
       return "spinbutton";
-    case "search":
+    }
+    case "search": {
       return "searchbox";
+    }
     case "button":
     case "image":
     case "reset":
-    case "submit":
+    case "submit": {
       return "button";
-    case "hidden":
+    }
+    case "hidden": {
       return undefined;
-    default:
+    }
+    default: {
       return "textbox";
+    }
   }
 }
 

diff --git a/src/rules/html-lang-valid.ts b/src/rules/html-lang-valid.ts
@@ -5,12 +5,19 @@ const text = "The lang attribute of the <html> element must have a valid value";
 const url = `https://dequeuniversity.com/rules/axe/4.11/${id}`;
 
 function langIsValid(locale: string): boolean {
+  // Extract the primary language subtag (before any hyphen).
+  // BCP 47 requires only the primary subtag to be a valid ISO 639 code;
+  // additional subtags (region, variant, etc.) don't affect validity for
+  // this rule.
+  const primarySubtag = locale.split("-")[0];
+  if (!primarySubtag) return false;
+
   try {
-    const foundLocales = Intl.DisplayNames.supportedLocalesOf([locale], {
+    const foundLocales = Intl.DisplayNames.supportedLocalesOf([primarySubtag], {
       localeMatcher: "lookup",
     });
     if (foundLocales.length !== 1) return false;
-    return foundLocales[0].toLowerCase() === locale.toLowerCase();
+    return foundLocales[0].toLowerCase() === primarySubtag.toLowerCase();
   } catch {
     return false;
   }

diff --git a/src/scanner.ts b/src/scanner.ts
@@ -39,6 +39,7 @@ import list from "./rules/list";
 import dlitem from "./rules/dlitem";
 import nestedInteractive from "./rules/nested-interactive";
 import validLang from "./rules/valid-lang";
+import htmlHasLang from "./rules/html-has-lang";
 import htmlLangValid from "./rules/html-lang-valid";
 import htmlXmlLangMismatch from "./rules/html-xml-lang-mismatch";
 import colorContrast from "./rules/color-contrast";
@@ -156,6 +157,7 @@ export const allRules: Rule[] = [
   frameTitle,
   frameTitleUnique,
   headingOrder,
+  htmlHasLang,
   htmlLangValid,
   htmlXmlLangMismatch,
   identicalLinksSamePurpose,

diff --git a/tests/act/tests/b5c3f8/0fac26928e2bf6b7db6c7f46a1e0ab50aaa8a7c1.ts b/tests/act/tests/b5c3f8/0fac26928e2bf6b7db6c7f46a1e0ab50aaa8a7c1.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[b5c3f8]HTML page has lang attribute", function () {
+  it("Passed Example 1 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/b5c3f8/0fac26928e2bf6b7db6c7f46a1e0ab50aaa8a7c1.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="en">
+	<body>
+		The quick brown fox jumps over the lazy dog.
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-has-lang"];
+    const relevant = results.filter(r => expectedUrls.includes(r.url));
+    expect(relevant).to.be.empty;
+  });
+});
diff --git a/tests/act/tests/b5c3f8/473352935acf2463b14dbd8e38073e913eeb5c08.ts b/tests/act/tests/b5c3f8/473352935acf2463b14dbd8e38073e913eeb5c08.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[b5c3f8]HTML page has lang attribute", function () {
+  it("Failed Example 1 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/b5c3f8/473352935acf2463b14dbd8e38073e913eeb5c08.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html>
+	<body>
+		The quick brown fox jumps over the lazy dog.
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-has-lang"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/b5c3f8/4ea0280617a1b71dcc327356484f8767919b0f40.ts b/tests/act/tests/b5c3f8/4ea0280617a1b71dcc327356484f8767919b0f40.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[b5c3f8]HTML page has lang attribute", function () {
+  it("Failed Example 3 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/b5c3f8/4ea0280617a1b71dcc327356484f8767919b0f40.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang=" ">
+	<body>
+		The quick brown fox jumps over the lazy dog.
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-has-lang"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/b5c3f8/4f94c3e26f43701d91db403fe26cd8894bdc8ccf.ts b/tests/act/tests/b5c3f8/4f94c3e26f43701d91db403fe26cd8894bdc8ccf.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[b5c3f8]HTML page has lang attribute", function () {
+  it("Failed Example 4 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/b5c3f8/4f94c3e26f43701d91db403fe26cd8894bdc8ccf.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html xml:lang="en">
+	<body>
+		The quick brown fox jumps over the lazy dog.
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-has-lang"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/b5c3f8/98681b2a7949e49b2da1b353f70e688528fe7ddc.ts b/tests/act/tests/b5c3f8/98681b2a7949e49b2da1b353f70e688528fe7ddc.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[b5c3f8]HTML page has lang attribute", function () {
+  it("Failed Example 2 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/b5c3f8/98681b2a7949e49b2da1b353f70e688528fe7ddc.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="">
+	<body>
+		The quick brown fox jumps over the lazy dog.
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-has-lang"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/bf051a/0f73e7179e17f050380f0ea350d2551611820fd5.ts b/tests/act/tests/bf051a/0f73e7179e17f050380f0ea350d2551611820fd5.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[bf051a]HTML page `lang` attribute has valid language tag", function () {
+  it("Failed Example 3 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/bf051a/0f73e7179e17f050380f0ea350d2551611820fd5.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="eng">
+	<body>
+		<p lang="en">I love ACT rules!</p>
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-lang-valid"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/bf051a/5c998eef8cb13a8f577dade1a3b9fe591bc69204.ts b/tests/act/tests/bf051a/5c998eef8cb13a8f577dade1a3b9fe591bc69204.ts
@@ -0,0 +1,19 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[bf051a]HTML page `lang` attribute has valid language tag", function () {
+  it("Failed Example 2 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/bf051a/5c998eef8cb13a8f577dade1a3b9fe591bc69204.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="#1"></html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-lang-valid"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/bf051a/7d8c4fd028c504d10c4e5e9bd7183c139549e1a1.ts b/tests/act/tests/bf051a/7d8c4fd028c504d10c4e5e9bd7183c139549e1a1.ts
@@ -0,0 +1,19 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[bf051a]HTML page `lang` attribute has valid language tag", function () {
+  it("Passed Example 1 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/bf051a/7d8c4fd028c504d10c4e5e9bd7183c139549e1a1.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="FR"></html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-lang-valid"];
+    const relevant = results.filter(r => expectedUrls.includes(r.url));
+    expect(relevant).to.be.empty;
+  });
+});
diff --git a/tests/act/tests/bf051a/a49f11c86ad81c4d42700dfca58a7eeec377f02e.ts b/tests/act/tests/bf051a/a49f11c86ad81c4d42700dfca58a7eeec377f02e.ts
@@ -0,0 +1,19 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[bf051a]HTML page `lang` attribute has valid language tag", function () {
+  it("Passed Example 2 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/bf051a/a49f11c86ad81c4d42700dfca58a7eeec377f02e.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="en-US-GB"></html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-lang-valid"];
+    const relevant = results.filter(r => expectedUrls.includes(r.url));
+    expect(relevant).to.be.empty;
+  });
+});
diff --git a/tests/act/tests/bf051a/b64d767d873269ff00966630e34ab198fc24368f.ts b/tests/act/tests/bf051a/b64d767d873269ff00966630e34ab198fc24368f.ts
@@ -0,0 +1,23 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[bf051a]HTML page `lang` attribute has valid language tag", function () {
+  it("Failed Example 4 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/bf051a/b64d767d873269ff00966630e34ab198fc24368f.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="i-lux">
+	<body>
+		<p lang="lb">Lëtzebuerg ass e Land an Europa.</p>
+	</body>
+</html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-lang-valid"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});
diff --git a/tests/act/tests/bf051a/b7a35f8080e756776877bca013a910dafde8ef73.ts b/tests/act/tests/bf051a/b7a35f8080e756776877bca013a910dafde8ef73.ts
@@ -0,0 +1,19 @@
+import { expect } from "@open-wc/testing";
+import { scan } from "../../../../src/scanner";
+
+const parser = new DOMParser();
+
+describe("[bf051a]HTML page `lang` attribute has valid language tag", function () {
+  it("Failed Example 1 (https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/bf051a/b7a35f8080e756776877bca013a910dafde8ef73.html)", async () => {
+    const document = parser.parseFromString(`<!DOCTYPE html>
+<html lang="em-US"></html>`, 'text/html');
+
+    const results = (await scan(document.body)).map(({ text, url }) => {
+      return { text, url };
+    });
+
+    expect(results).to.not.be.empty;
+    const expectedUrls = ["https://dequeuniversity.com/rules/axe/4.11/html-lang-valid"];
+    expect(results.some(r => expectedUrls.includes(r.url))).to.be.true;
+  });
+});