Implement ask_for_reset for HTMLSelectElement.

Fixes #7774

components/script/dom/htmloptionelement.rs

@@ -14,6 +14,7 @@ use dom::document::Document;
 use dom::element::{AttributeMutation, Element, IN_ENABLED_STATE};
 use dom::htmlelement::HTMLElement;
 use dom::htmlscriptelement::HTMLScriptElement;
+use dom::htmlselectelement::HTMLSelectElement;
 use dom::node::Node;
 use dom::text::Text;
 use dom::virtualmethods::VirtualMethods;
@@ -51,6 +52,10 @@ impl HTMLOptionElement {
         let element = HTMLOptionElement::new_inherited(localName, prefix, document);
         Node::reflect_node(box element, document, HTMLOptionElementBinding::Wrap)
     }
+
+    pub fn set_selectedness(&self, selected: bool) {
+        self.selectedness.set(selected);
+    }
 }
 
 fn collect_text(element: &Element, value: &mut DOMString) {
@@ -134,8 +139,10 @@ impl HTMLOptionElementMethods for HTMLOptionElement {
     fn SetSelected(&self, selected: bool) {
         self.dirtiness.set(true);
         self.selectedness.set(selected);
-        // FIXME: as per the spec, implement 'ask for a reset'
-        // https://github.com/servo/servo/issues/7774
+        if let Some(select) = self.upcast::<Node>().ancestors()
+            .filter_map(Root::downcast::<HTMLSelectElement>).next() {
+                select.ask_for_reset();
+        }
     }
 }
 

components/script/dom/htmlselectelement.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::attr::{Attr, AttrValue};
+use dom::bindings::codegen::Bindings::HTMLOptionElementBinding::HTMLOptionElementMethods;
 use dom::bindings::codegen::Bindings::HTMLSelectElementBinding;
 use dom::bindings::codegen::Bindings::HTMLSelectElementBinding::HTMLSelectElementMethods;
 use dom::bindings::codegen::UnionTypes::HTMLElementOrLong;
@@ -14,6 +15,7 @@ use dom::element::{AttributeMutation, Element, IN_ENABLED_STATE};
 use dom::htmlelement::HTMLElement;
 use dom::htmlfieldsetelement::HTMLFieldSetElement;
 use dom::htmlformelement::{FormControl, HTMLFormElement};
+use dom::htmloptionelement::HTMLOptionElement;
 use dom::node::{Node, window_from_node};
 use dom::validitystate::ValidityState;
 use dom::virtualmethods::VirtualMethods;
@@ -46,6 +48,53 @@ impl HTMLSelectElement {
         let element = HTMLSelectElement::new_inherited(localName, prefix, document);
         Node::reflect_node(box element, document, HTMLSelectElementBinding::Wrap)
     }
+
+    // https://html.spec.whatwg.org/multipage/#ask-for-a-reset
+    pub fn ask_for_reset(&self) {
+        if self.Multiple() {
+            return;
+        }
+
+        let mut first_enabled: Option<Root<HTMLOptionElement>> = None;
+        let mut last_selected: Option<Root<HTMLOptionElement>> = None;
+
+        let node = self.upcast::<Node>();
+        for opt in node.traverse_preorder().filter_map(Root::downcast::<HTMLOptionElement>) {
+            if opt.Selected() {
+                opt.set_selectedness(false);
+                last_selected = Some(Root::from_ref(opt.r()));
+            }
+            let element =  opt.upcast::<Element>();
+            if first_enabled.is_none() && !element.get_disabled_state() {
+                first_enabled = Some(Root::from_ref(opt.r()));
+            }
+        }
+
+        if last_selected.is_none() {
+            if self.display_size() == 1 {
+                // select the first enabled element
+                if let Some(first_opt) = first_enabled {
+                    first_opt.set_selectedness(true);
+                }
+            }
+        } else {
+            // >= 1 selected, reselect last one
+            last_selected.unwrap().set_selectedness(true);
+        }
+    }
+
+   // https://html.spec.whatwg.org/multipage/#concept-select-size
+   fn display_size(&self) -> u32 {
+        if self.Size() == 0 {
+            if self.Multiple() {
+                4
+            } else {
+                1
+            }
+        } else {
+            self.Size()
+        }
+    }
 }
 
 impl HTMLSelectElementMethods for HTMLSelectElement {

tests/wpt/metadata/MANIFEST.json

@@ -17917,6 +17917,10 @@
         "path": "html/semantics/forms/the-select-element/select-remove.html",
         "url": "/html/semantics/forms/the-select-element/select-remove.html"
       },
+      {
+        "path": "html/semantics/forms/the-select-element/select-ask-for-reset.html",
+        "url": "/html/semantics/forms/the-select-element/select-ask-for-reset.html"
+      },
       {
         "path": "html/semantics/forms/the-textarea-element/textarea-type.html",
         "url": "/html/semantics/forms/the-textarea-element/textarea-type.html"

tests/wpt/web-platform-tests/html/semantics/forms/the-select-element/select-ask-for-reset.html

@@ -0,0 +1,73 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>HTMLSelectElement ask for reset</title>
+<link rel="author" title="Dongie Agnir" href="dongie.agnir@gmail.com">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id=log></div>
+<script>
+test(function() {
+  var select = makeSelect(5);
+
+  select.children[4].selected = true;
+  unselectedExcept(select, 4);
+
+  select.children[4].remove();
+  unselectedExcept(select, 0); // remove selected node, should default to first
+
+  select.children[3].selected = true;
+
+  select.children[0].remove();
+  unselectedExcept(select, 2); // last node still selected
+}, "ask for reset on node remove, non multiple.");
+
+test(function() {
+  var select = makeSelect(3);
+  select.children[1].selected = true;
+
+  var opt4 = document.createElement("option");
+  opt4.selected = true;
+  select.appendChild(opt4); // 2 options selected
+  unselectedExcept(select, 3); // last should remain selected
+
+  var opt5 = document.createElement("option");
+  select.appendChild(opt5);
+
+  unselectedExcept(select, 3); // no change in selected element
+  }, "ask for reset on node insert, non multiple.");
+
+test(function() {
+  var select = makeSelect(3);
+
+  select.children[2].selected = true;
+  select.children[2].selected = false; // none selected
+  unselectedExcept(select, 0);
+
+  // disable first so option at index 1 is first eligible
+  select.children[0].disabled = true;
+  select.children[2].selected = true;
+  select.children[2].selected = false; // none selected
+  unselectedExcept(select, 1);
+}, "change selectedness of option, non multiple.");
+
+
+function unselectedExcept(sel, opt) {
+  for (var i = 0; i < sel.children.length; ++i) {
+    if (i != opt) {
+      assert_false(sel.children[i].selected, "option should not be selected.");
+    }
+    if (opt != null) {
+      assert_true(sel.children[opt].selected, "option should be selected.");
+    }
+  }
+}
+
+function makeSelect(n) {
+  var sel = document.createElement("select");
+  for (var i = 0; i < n; ++i) {
+    opt = document.createElement("option");
+    sel.appendChild(opt);
+  }
+  return sel;
+}
+</script>