feat: add support for proper tracking in a speculative pre-rendering …

…context (#102)

* feat: add support for proper tracking in a speculative pre-rendering context

* test: add unit tests

src/setup.js

@@ -40,5 +40,10 @@ export function setup() {
 /* c8 ignore next 18 */
 export function init() {
   setup();
-  sampleRUM();
+  // Prerender-aware initialization
+  if (document.prerendering) {
+    document.addEventListener('prerenderingchange', sampleRUM, { once: true });
+  } else {
+    sampleRUM();
+  }
 }

test/setup/setup.test.html

@@ -8,7 +8,7 @@
       /* eslint-env mocha */
       import { runTests } from '@web/test-runner-mocha';
       import { expect } from '@esm-bundle/chai';
-      import { setup } from '../../src/setup.js';
+      import { setup, init } from '../../src/setup.js';
 
       runTests(() => {
         it('setup - defines window.hlx', () => {
@@ -33,6 +33,14 @@
           expect(window.hlx.codeBasePath).to.be.equal('/some/path');
           expect(window.hlx.lighthouse).to.be.false;
         });
+
+        it('init - does not enable RUM during prerendering', () => {
+          Object.defineProperty(document, 'prerendering', { value: true });
+          init();
+          expect(window.hlx.rum).to.be.undefined;
+          document.dispatchEvent(new Event('prerenderingchange'));
+          expect(window.hlx.rum).to.not.be.undefined;
+        });
       });
     </script>
   </body>