webapi: implement HTMLSelectElement.type and HTMLOptionElement.label

Both IDL attributes were unimplemented and evaluated to `undefined`.
`select.type` reflects the element's mode: "select-multiple" when the
`multiple` attribute is present, "select-one" otherwise (derived from the
existing `getMultiple()`). `option.label` returns the `label` content
attribute when present and non-empty, otherwise the value of the `text`
IDL attribute. Both match the HTML Living Standard.

Select-enhancement libraries branch on `select.type` to choose single- vs
multi-select code paths; reading `undefined` there made them take a dead
path and throw during initialization.

Closes #2738

src/browser/tests/element/html/option.html

@@ -29,6 +29,23 @@
   testing.expectEqual('Text 3', $('#opt3').text)
 </script>
 
+<option id="opt_labelled" label="Explicit Label">Inner Text</option>
+
+<script id="label">
+  // https://html.spec.whatwg.org/multipage/form-elements.html#dom-option-label
+  // No label attribute: falls back to the text.
+  testing.expectEqual('Text 1', $('#opt1').label)
+  // label attribute present and non-empty: returned as-is.
+  testing.expectEqual('Explicit Label', $('#opt_labelled').label)
+  // Setting reflects to the label content attribute.
+  $('#opt1').label = 'Set Label'
+  testing.expectEqual('Set Label', $('#opt1').label)
+  testing.expectEqual('Set Label', $('#opt1').getAttribute('label'))
+  // An empty label attribute falls back to the text, per spec.
+  $('#opt1').setAttribute('label', '')
+  testing.expectEqual('Text 1', $('#opt1').label)
+</script>
+
 <script id="text_set">
   $('#opt1').text = 'New Text 1'
   testing.expectEqual('New Text 1', $('#opt1').text)

src/browser/tests/element/html/select.html

@@ -142,6 +142,20 @@
   }
 </script>
 
+<script id="type_reflects_multiple">
+  {
+    // https://html.spec.whatwg.org/multipage/form-elements.html#dom-select-type
+    testing.expectEqual('select-one', $('#select1').type)
+    testing.expectEqual('select-multiple', $('#select_multi').type)
+
+    // type tracks the multiple attribute, it is not stored independently
+    const sel = document.createElement('select')
+    testing.expectEqual('select-one', sel.type)
+    sel.multiple = true
+    testing.expectEqual('select-multiple', sel.type)
+  }
+</script>
+
 <script id="multiple_setValue">
   {
     const sel = $('#select_multi')

src/browser/webapi/element/html/Option.zig

@@ -108,6 +108,21 @@ pub fn setName(self: *Option, name: []const u8, frame: *Frame) !void {
     try self.asElement().setAttributeSafe(comptime .wrap("name"), .wrap(name), frame);
 }
 
+// https://html.spec.whatwg.org/multipage/form-elements.html#dom-option-label
+// On getting, return the `label` content attribute if present and non-empty,
+// otherwise the value of the `text` IDL attribute. On setting, reflect to the
+// `label` content attribute.
+pub fn getLabel(self: *const Option, frame: *Frame) []const u8 {
+    if (self.asConstElement().getAttributeSafe(comptime .wrap("label"))) |label| {
+        if (label.len != 0) return label;
+    }
+    return self.getText(frame);
+}
+
+pub fn setLabel(self: *Option, label: []const u8, frame: *Frame) !void {
+    try self.asElement().setAttributeSafe(comptime .wrap("label"), .wrap(label), frame);
+}
+
 pub const JsApi = struct {
     pub const bridge = js.Bridge(Option);
 
@@ -119,6 +134,7 @@ pub const JsApi = struct {
 
     pub const value = bridge.accessor(Option.getValue, Option.setValue, .{ .ce_reactions = true });
     pub const text = bridge.accessor(Option.getText, Option.setText, .{ .ce_reactions = true });
+    pub const label = bridge.accessor(Option.getLabel, Option.setLabel, .{ .ce_reactions = true });
     pub const selected = bridge.accessor(Option.getSelected, Option.setSelected, .{});
     pub const defaultSelected = bridge.accessor(Option.getDefaultSelected, null, .{});
     pub const disabled = bridge.accessor(Option.getDisabled, Option.setDisabled, .{ .ce_reactions = true });

src/browser/webapi/element/html/Select.zig

@@ -129,6 +129,13 @@ pub fn getMultiple(self: *const Select) bool {
     return self.asConstElement().getAttributeSafe(comptime .wrap("multiple")) != null;
 }
 
+// https://html.spec.whatwg.org/multipage/form-elements.html#dom-select-type
+// The `type` IDL attribute reflects the element's mode: "select-multiple" when
+// the `multiple` attribute is present, "select-one" otherwise.
+pub fn getType(self: *const Select) []const u8 {
+    return if (self.getMultiple()) "select-multiple" else "select-one";
+}
+
 pub fn setMultiple(self: *Select, multiple: bool, frame: *Frame) !void {
     if (multiple) {
         try self.asElement().setAttributeSafe(comptime .wrap("multiple"), .wrap(""), frame);
@@ -318,6 +325,7 @@ pub const JsApi = struct {
     };
 
     pub const value = bridge.accessor(Select.getValue, Select.setValue, .{});
+    pub const @"type" = bridge.accessor(Select.getType, null, .{});
     pub const selectedIndex = bridge.accessor(Select.getSelectedIndex, Select.setSelectedIndex, .{});
     pub const multiple = bridge.accessor(Select.getMultiple, Select.setMultiple, .{ .ce_reactions = true });
     pub const disabled = bridge.accessor(Select.getDisabled, Select.setDisabled, .{ .ce_reactions = true });