Bug 1776190 - [marionette] Allow a modifier key to be reset when sending it again within the same command. r=webdriver-reviewers,jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D175242

remote/marionette/event.sys.mjs

@@ -262,7 +262,12 @@ event.sendKeys = function(keyString, win) {
     const data = lazy.keyData.getData(keyValue);
     const key = { ...data, ...modifiers };
     if (data.modifier) {
-      modifiers[data.modifier] = true;
+      // Negating the state of the modifier here is not spec compliant but
+      // makes us compatible to Chrome's behavior for now. That's fine unless
+      // we know the correct behavior.
+      //
+      // @see: https://github.com/w3c/webdriver/issues/1734
+      modifiers[data.modifier] = !modifiers[data.modifier];
     }
     event.sendSingleKey(key, win);
   }

testing/web-platform/mozilla/tests/webdriver/element_send_keys/send_keys.py

@@ -0,0 +1,24 @@
+from tests.support.asserts import assert_success
+from tests.support.keys import Keys
+
+
+def element_send_keys(session, element, text):
+    return session.transport.send(
+        "POST",
+        "/session/{session_id}/element/{element_id}/value".format(
+            session_id=session.session_id, element_id=element.id
+        ),
+        {"text": text},
+    )
+
+
+def test_modifier_key_toggles(session, inline, modifier_key):
+    session.url = inline("<input type=text value=foo>")
+    element = session.find.css("input", all=False)
+
+    response = element_send_keys(
+        session, element, f"{modifier_key}a{modifier_key}{Keys.DELETE}cheese"
+    )
+    assert_success(response)
+
+    assert element.property("value") == "cheese"