Bug 1631693: Expose value on non-editable ARIA comboboxes, r=Jamie

This revision expands the reporting of ARIA combobox values to non-editable
comboboxes with no selected option. In these cases, according to the spec, we
should report a value "represented by its descendant elements [...] determined
using the same method used to compute the name of a button from its descendant
content." In this revision, I interpret that to mean, roughly, nsTextEquivUtils'
GetTextEquivFromSubtree, which is tantamount to the name calculation, except
that it crucially avoids rejecting the combobox for having eNameFromValueRule,
unlike GetNameFromSubtree. This revision updates this logic in LocalAccessible
and RemoteAccessibleBase, and adds tests to verify the above.

Differential Revision: https://phabricator.services.mozilla.com/D162229

accessible/generic/LocalAccessible.cpp

@@ -1641,7 +1641,9 @@ void LocalAccessible::Value(nsString& aValue) const {
       }
     }
 
-    if (option) nsTextEquivUtils::GetTextEquivFromSubtree(option, aValue);
+    // If there's a selected item, get the value from it. Otherwise, determine
+    // the value from descendant elements.
+    nsTextEquivUtils::GetTextEquivFromSubtree(option ? option : this, aValue);
   }
 }
 

accessible/ipc/RemoteAccessibleBase.cpp

@@ -267,6 +267,9 @@ void RemoteAccessibleBase<Derived>::Value(nsString& aValue) const {
           const_cast<RemoteAccessibleBase<Derived>*>(this)->GetSelectedItem(0);
       if (option) {
         option->Name(aValue);
+      } else {
+        // If no selected item, determine the value from descendant elements.
+        nsTextEquivUtils::GetTextEquivFromSubtree(this, aValue);
       }
       return;
     }

accessible/tests/browser/e10s/browser_caching_value.js

@@ -316,5 +316,69 @@ addAccessibleTask(
       "Select value correct after changing option back"
     );
   },
-  { chrome: true, topLevel: true, iframe: true, remoteIFrame: true }
+  { chrome: true, topLevel: true, iframe: true, remoteIframe: true }
+);
+
+/**
+ * Test combobox values for non-editable comboboxes.
+ */
+addAccessibleTask(
+  `
+  <div id="combo-div-1" role="combobox">value</div>
+  <div id="combo-div-2" role="combobox">
+    <div role="listbox">
+      <div role="option">value</div>
+    </div>
+  </div>
+  <div id="combo-div-3" role="combobox">
+    <div role="group">value</div>
+  </div>
+  <div id="combo-div-4" role="combobox">foo
+    <div role="listbox">
+      <div role="option">bar</div>
+    </div>
+  </div>
+
+  <input id="combo-input-1" role="combobox" value="value" disabled></input>
+  <input id="combo-input-2" role="combobox" value="value" disabled>testing</input>
+
+  <div id="combo-div-selected" role="combobox">
+    <div role="listbox">
+      <div aria-selected="true" role="option">value</div>
+    </div>
+  </div>
+`,
+  async function(browser, docAcc) {
+    const comboDiv1 = findAccessibleChildByID(docAcc, "combo-div-1");
+    const comboDiv2 = findAccessibleChildByID(docAcc, "combo-div-2");
+    const comboDiv3 = findAccessibleChildByID(docAcc, "combo-div-3");
+    const comboDiv4 = findAccessibleChildByID(docAcc, "combo-div-4");
+    const comboInput1 = findAccessibleChildByID(docAcc, "combo-input-1");
+    const comboInput2 = findAccessibleChildByID(docAcc, "combo-input-2");
+    const comboDivSelected = findAccessibleChildByID(
+      docAcc,
+      "combo-div-selected"
+    );
+
+    // Text as a descendant of the combobox: included in the value.
+    is(comboDiv1.value, "value", "Combobox value correct");
+
+    // Text as the descendant of a listbox: excluded from the value.
+    is(comboDiv2.value, "", "Combobox value correct");
+
+    // Text as the descendant of some other role that includes text in name computation.
+    // Here, the group role contains the text node with "value" in it.
+    is(comboDiv3.value, "value", "Combobox value correct");
+
+    // Some descendant text included, but text descendant of a listbox excluded.
+    is(comboDiv4.value, "foo", "Combobox value correct");
+
+    // Combobox inputs with explicit value report that value.
+    is(comboInput1.value, "value", "Combobox value correct");
+    is(comboInput2.value, "value", "Combobox value correct");
+
+    // Combobox role with aria-selected reports correct value.
+    is(comboDivSelected.value, "value", "Combobox value correct");
+  },
+  { chrome: true, iframe: true, remoteIframe: true }
 );