From 4cb5ec686a5806fa18ae6a1b33249ea1c8888abb Mon Sep 17 00:00:00 2001
From: Matthew Noorenberghe <mozilla@noorenberghe.ca>
Date: Tue, 31 Jan 2017 23:54:45 -0800
Subject: [PATCH] Bug 1330111 - Add FormLikeFactory.findRootForField API.
 r=johannh

MozReview-Commit-ID: 6qo0hVx3J6p
---
 toolkit/modules/FormLikeFactory.jsm | 31 +++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/toolkit/modules/FormLikeFactory.jsm b/toolkit/modules/FormLikeFactory.jsm
index 8052f1ed00bc..45f25187c6e7 100644
--- a/toolkit/modules/FormLikeFactory.jsm
+++ b/toolkit/modules/FormLikeFactory.jsm
@@ -68,13 +68,16 @@ let FormLikeFactory = {
       throw new Error("createFromField requires a field in a document");
     }
 
-    if (aField.form) {
-      return this.createFromForm(aField.form);
+    let rootElement = this.findRootForField(aField);
+    if (rootElement instanceof Ci.nsIDOMHTMLFormElement) {
+      return this.createFromForm(rootElement);
     }
 
     let doc = aField.ownerDocument;
     let elements = [];
-    for (let el of doc.documentElement.querySelectorAll("input")) {
+    for (let el of rootElement.querySelectorAll("input")) {
+      // Exclude elements inside the rootElement that are already in a <form> as
+      // they will be handled by their own FormLike.
       if (!el.form) {
         elements.push(el);
       }
@@ -82,17 +85,33 @@ let FormLikeFactory = {
     let formLike = {
       action: doc.baseURI,
       autocomplete: "on",
-      // Exclude elements inside the rootElement that are already in a <form> as
-      // they will be handled by their own FormLike.
       elements,
       ownerDocument: doc,
-      rootElement: doc.documentElement,
+      rootElement,
     };
 
     this._addToJSONProperty(formLike);
     return formLike;
   },
 
+  /**
+   * Determine the Element that encapsulates the related fields. For example, if
+   * a page contains a login form and a checkout form which are "submitted"
+   * separately, and the username field is passed in, ideally this would return
+   * an ancestor Element of the username and password fields which doesn't
+   * include any of the checkout fields.
+   *
+   * @param {HTMLInputElement} aField - a field in a document
+   * @return {HTMLElement} - the root element surrounding related fields
+   */
+  findRootForField(aField) {
+    if (aField.form) {
+      return aField.form;
+    }
+
+    return aField.ownerDocument.documentElement;
+  },
+
   /**
    * Add a `toJSON` property to a FormLike so logging which ends up going
    * through dump doesn't include usless garbage from DOM objects.