Fix dynamic extension path (ampproject#19340)

* handle esm case

* fix how we dynamically fetch scripts for single pass experiment

* fix tests

* remove erroneous arg

* store path in var

src/service/extension-location.js

@@ -45,6 +45,15 @@ function calculateScriptBaseUrl(location, opt_isLocalDev) {
   return urls.cdn;
 }
 
+/**
+ * Calculates if we need a single pass folder or not.
+ *
+ * @return {string}
+ */
+function getSinglePassExperimentPath() {
+  return getMode().singlePassType ? `${getMode().singlePassType}/` : '';
+}
+
 /**
  * Calculate script url for an extension.
  * @param {!Location} location The window's location
@@ -63,7 +72,8 @@ export function calculateExtensionScriptUrl(location, extensionId,
   const extensionVersion = opt_extensionVersion
     ? '-' + opt_extensionVersion
     : '';
-  return `${base}/rtv/${rtv}/v0/${extensionId}${extensionVersion}.js`;
+  const spPath = getSinglePassExperimentPath();
+  return `${base}/rtv/${rtv}/${spPath}v0/${extensionId}${extensionVersion}.js`;
 }
 
 /**
@@ -79,7 +89,8 @@ export function calculateEntryPointScriptUrl(
   location, entryPoint, isLocalDev, opt_rtv) {
   const base = calculateScriptBaseUrl(location, isLocalDev);
   if (opt_rtv) {
-    return `${base}/rtv/${getMode().rtvVersion}/${entryPoint}.js`;
+    const spPath = getSinglePassExperimentPath();
+    return `${base}/rtv/${getMode().rtvVersion}/${spPath}${entryPoint}.js`;
   }
   return `${base}/${entryPoint}.js`;
 }

test/functional/test-extension-location.js

@@ -67,6 +67,17 @@ describes.sandboxed('Extension Location', {}, () => {
       expect(script).to.equal(
           'http://localhost:8000/dist/rtv/123/v0/no-version.js');
     });
+
+    it('should handles single pass experiment', () => {
+      window.AMP_MODE = {rtvVersion: '123', singlePassType: 'sp'};
+      const script = calculateExtensionScriptUrl({
+        pathname: 'examples/ads.amp.html',
+        host: 'localhost:8000',
+        protocol: 'http:',
+      }, 'no-version', /* version is empty but defined */ '', true);
+      expect(script).to.equal(
+          'http://localhost:8000/dist/rtv/123/sp/v0/no-version.js');
+    });
   });
 
   describe('get correct entry point source', () => {
@@ -109,6 +120,17 @@ describes.sandboxed('Extension Location', {}, () => {
       expect(script).to.equal(
           'https://cdn.ampproject.org/rtv/123/ww.js');
     });
+
+    it('should handle single pass experiment', () => {
+      window.AMP_MODE = {rtvVersion: '123', singlePassType: 'sp'};
+      const script = calculateEntryPointScriptUrl({
+        pathname: 'examples/ads.amp.html',
+        host: 'localhost:8000',
+        protocol: 'http:',
+      }, 'ww', /* isLocalDev */ false, /* opt_rtv */ true);
+      expect(script).to.equal(
+          'https://cdn.ampproject.org/rtv/123/sp/ww.js');
+    });
   });
 
   describe('get correct URL parts', () => {