Install global submit listener only when amp-form extension is registered

src/document-submit.js

@@ -27,14 +27,21 @@ import {isExtensionScriptInNode} from './element-service';
 
 /**
  * @param {!./service/ampdoc-impl.AmpDoc} ampdoc
+ * @return {!Promise}
  */
 export function installGlobalSubmitListenerForDoc(ampdoc) {
   // Register global submit event listener only if the amp-form
   // extension is used. Allowing the usage of native forms, otherwise.
-  if (isExtensionScriptInNode(ampdoc.getHeadNode(), 'amp-form')) {
-    ampdoc.getRootNode().addEventListener(
-        'submit', onDocumentFormSubmit_, true);
-  }
+  return isExtensionScriptInNode(
+      ampdoc.win,
+      ampdoc.getHeadNode(),
+      'amp-form')
+      .then(isAmpFormExtension => {
+        if (isAmpFormExtension) {
+          ampdoc.getRootNode().addEventListener(
+              'submit', onDocumentFormSubmit_, true);
+        }
+      });
 }
 
 

src/element-service.js

@@ -203,14 +203,29 @@ export function extensionScriptsInNode(head) {
   return scripts;
 }
 
+/**
+ * Waits for body to be present then verifies that an extension script is
+ * present in head for installation.
+ * @param {!Window} win
+ * @param {HTMLHeadElement|Element|ShadowRoot} head
+ * @param {string} extensionId
+ * @return {!Promise<boolean>}
+ */
+export function isExtensionScriptInNode(win, head, extensionId) {
+  return dom.waitForBodyPromise(win.document)
+      .then(() => {
+        return extensionScriptInNode(head, extensionId);
+      });
+}
+
 /**
  * Verifies that an extension script is present in head for
  * installation.
  * @param {HTMLHeadElement|Element|ShadowRoot} head
  * @param {string} extensionId
- * @return {boolean}
+ * @private
  */
-export function isExtensionScriptInNode(head, extensionId) {
+function extensionScriptInNode(head, extensionId) {
   return extensionScriptsInNode(head).includes(extensionId);
 }
 
@@ -233,7 +248,7 @@ function waitForExtensionIfPresent(win, extension, head) {
 
   // TODO(jpettitt) investigate registerExtension to short circuit
   // the dom call in extensionScriptsInNode()
-  if (!isExtensionScriptInNode(head, extension)) {
+  if (!extensionScriptInNode(head, extension)) {
     return Promise.resolve();
   }
 

test/functional/test-document-submit.js

@@ -47,38 +47,46 @@ describe('test-document-submit onDocumentFormSubmit_', () => {
   });
 
   describe('installGlobalSubmitListenerForDoc', () => {
-    let ampDoc;
+    let ampdoc;
     let headNode;
     let rootNode;
     beforeEach(() => {
       headNode = document.createElement('head');
       rootNode = document.createElement('html');
-      ampDoc = {
+      ampdoc = {
         getHeadNode: () => headNode,
         getRootNode: () => rootNode,
+        win: {document: {documentElement: {body: {}}}},
       };
     });
 
+    /**
+     * @param {string} extension
+     */
+    const createScript = extension => {
+      const script = document.createElement('script');
+      script.setAttribute('src',
+          'https://cdn.ampproject.org/v0/' + extension + '-0.1.js');
+      script.setAttribute('custom-element', extension);
+      return script;
+    };
+
     it('should not register submit listener if amp-form is not registered.',
         () => {
-          const script = document.createElement('script');
-          script.setAttribute('src', 'https://cdn.ampproject.org/v0/amp-list-0.1.js');
-          script.setAttribute('custom-element', 'amp-list');
-          ampDoc.getHeadNode().appendChild(script);
+          ampdoc.getHeadNode().appendChild(createScript('amp-list'));
           sandbox.spy(rootNode, 'addEventListener');
-          installGlobalSubmitListenerForDoc(ampDoc);
-          expect(rootNode.addEventListener).not.to.have.been.called;
+          installGlobalSubmitListenerForDoc(ampdoc).then(() => {
+            expect(rootNode.addEventListener).not.to.have.been.called;
+          });
         });
 
     it('should register submit listener if amp-form extension is registered.',
         () => {
-          const script = document.createElement('script');
-          script.setAttribute('src', 'https://cdn.ampproject.org/v0/amp-form-0.1.js');
-          script.setAttribute('custom-element', 'amp-form');
-          ampDoc.getHeadNode().appendChild(script);
+          ampdoc.getHeadNode().appendChild(createScript('amp-form'));
           sandbox.spy(rootNode, 'addEventListener');
-          installGlobalSubmitListenerForDoc(ampDoc);
-          expect(rootNode.addEventListener).called;
+          installGlobalSubmitListenerForDoc(ampdoc).then(() => {
+            expect(rootNode.addEventListener).called;
+          });
         });
   });
 

test/functional/test-element-service.js

@@ -337,10 +337,12 @@ describes.realWin('in single ampdoc', {
       extension.setAttribute('custom-element', 'amp-form');
       extension.setAttribute('src', 'https://cdn.ampproject.org/v0/amp-form-0.1.js');
       ampdoc.getHeadNode().appendChild(extension);
-      expect(isExtensionScriptInNode(
-          ampdoc.getHeadNode(), 'amp-form')).to.equal(true);
-      expect(isExtensionScriptInNode(
-          ampdoc.getHeadNode(), 'amp-list')).to.equal(false);
+      return isExtensionScriptInNode(
+          ampdoc.win,
+          ampdoc.getHeadNode(),
+          'amp-form').then(isAmpForminNode => {
+        expect(isAmpForminNode).to.equal(true);
+      });
     });
   });
 });