♻️Make loadScript function in validator-integration Trusted Types compatible (ampproject#38703)

* Make loadScript in validator-integration Trusted Types compatible

* Lint fix

* Disable lint to avoid forbidden term error

* Add missing https:// to url comparison

* Update test url to include https://

* Add explanation of why we use the explicit cdn domain

Author: eozmen410

Diff for: src/validator-integration.js

@@ -44,7 +44,29 @@ export function loadScript(doc, url) {
   const script = /** @type {!HTMLScriptElement} */ (
     doc.createElement('script')
   );
-  script.src = url;
+  // Make script.src assignment Trusted Types compatible for compatible browsers
+  if (self.trustedTypes && self.trustedTypes.createPolicy) {
+    const policy = self.trustedTypes.createPolicy(
+      'validator-integration#loadScript',
+      {
+        createScriptURL: function (url) {
+          // Only allow trusted URLs
+          // Using explicit cdn domain as no other AMP Cache hosts validator_
+          // wasm so we can assume the explicit cdn domain is cdn.ampproject.org
+          // instead of using the dynamic cdn value from src/config/urls.js
+          // eslint-disable-next-line local/no-forbidden-terms
+          if (url === 'https://cdn.ampproject.org/v0/validator_wasm.js') {
+            return url;
+          } else {
+            return '';
+          }
+        },
+      }
+    );
+    script.src = policy.createScriptURL(url);
+  } else {
+    script.src = url;
+  }
   propagateNonce(doc, script);
 
   const promise = loadPromise(script).then(

Diff for: test/unit/test-validator-integration.js

@@ -71,7 +71,10 @@ describes.fakeWin('validator-integration', {}, (env) => {
         .stub(eventHelper, 'loadPromise')
         .returns(Promise.resolve());
 
-      loadScript(win.document, 'http://example.com');
+      loadScript(
+        win.document,
+        'https://cdn.ampproject.org/v0/validator_wasm.js'
+      );
 
       expect(loadScriptStub).calledWith(
         env.sandbox.match((el) => el.nonce === '123')