Update IE driver to return NoSuchElement on JavaScript atom errors

Hitting a JavaScript error with the atom is an unrecoverable error. The
most common case of this for IE is when there is a page refresh,
navigation, or similar, and the driver is polling for element presence.
The calling code can't do anything about it, so we might as well just log
and return "no such element" error code. In the common case, this means
that the error will be transitory, and will sort itself out once the DOM
returns to normal after the page transition is completed. Note carefully
that this is an extreme hack, and has the potential to be masking a very
serious problem in the driver.

Author: jimevans

cpp/iedriver/ElementFinder.cpp

@@ -75,8 +75,20 @@ int ElementFinder::FindElement(const IECommandExecutor& executor,
       Json::Value atom_value = atom_result["value"];
       status_code = atom_status_code;
       *found_element = atom_result["value"];
-    } else {
-      *found_element = "A JavaScript error was encountered executing the findElement atom.";
+    }
+    else {
+      // Hitting a JavaScript error with the atom is an unrecoverable
+      // error. The most common case of this for IE is when there is a
+      // page refresh, navigation, or similar, and the driver is polling
+      // for element presence. The calling code can't do anything about
+      // it, so we might as well just log and return the "no such element"
+      // error code. In the common case, this means that the error will be
+      // transitory, and will sort itself out once the DOM returns to normal
+      // after the page transition is completed. Note carefully that this
+      // is an extreme hack, and has the potential to be papering over a
+      // very serious problem in the driver.
+      status_code = ENOSUCHELEMENT;
+      LOG(WARN) << "A JavaScript error was encountered executing the findElement atom.";
     }
   } else {
     LOG(WARN) << "Unable to get browser";
@@ -132,7 +144,15 @@ int ElementFinder::FindElements(const IECommandExecutor& executor,
       status_code = atom_status_code;
       *found_elements = atom_result["value"];
     } else {
-      *found_elements = "A JavaScript error was encountered executing the findElements atom.";
+      // Hitting a JavaScript error with the atom is an unrecoverable
+      // error. The most common case of this for IE is when there is a
+      // page refresh, navigation, or similar, and the driver is polling
+      // for element presence. The calling code can't do anything about
+      // it, so we might as well just log and return In the common case,
+      // this means that the error will be transitory, and will sort
+      // itself out once the DOM returns to normal after the page transition
+      // is completed.
+      LOG(WARN) << "A JavaScript error was encountered executing the findElements atom.";
     }
   } else {
     LOG(WARN) << "Unable to get browser";