codegen: Throw a more descriptive invalid enum message

components/script/dom/bindings/codegen/CodegenRust.py

@@ -662,11 +662,11 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
                  '%s' % (firstCap(sourceDescription), exceptionCode))),
             post="\n")
 
-    def onFailureInvalidEnumValue(failureCode):
+    def onFailureInvalidEnumValue(failureCode, passedVarName):
         return CGGeneric(
             failureCode or
-            ('throw_type_error(cx, "%s is not a valid enum value."); %s'
-             % (firstCap(sourceDescription), exceptionCode)))
+            ('throw_type_error(cx, &format!("\'{}\' is not a valid enum value for enumeration \'%s\'.", %s)); %s'
+             % (type.name, passedVarName, exceptionCode)))
 
     def onFailureNotCallable(failureCode):
         return CGGeneric(
@@ -873,15 +873,15 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
                             "yet")
         enum = type.inner.identifier.name
         if invalidEnumValueFatal:
-            handleInvalidEnumValueCode = onFailureInvalidEnumValue(failureCode).define()
+            handleInvalidEnumValueCode = onFailureInvalidEnumValue(failureCode, 'search').define()
         else:
             handleInvalidEnumValueCode = "return true;"
 
         template = (
             "match find_enum_string_index(cx, ${val}, %(values)s) {\n"
             "    Err(_) => { %(exceptionCode)s },\n"
-            "    Ok(None) => { %(handleInvalidEnumValueCode)s },\n"
-            "    Ok(Some(index)) => {\n"
+            "    Ok((None, search)) => { %(handleInvalidEnumValueCode)s },\n"
+            "    Ok((Some(index), _)) => {\n"
             "        //XXXjdm need some range checks up in here.\n"
             "        mem::transmute(index)\n"
             "    },\n"

components/script/dom/bindings/utils.rs

@@ -39,6 +39,7 @@ use std::ptr;
 use std::slice;
 use util::non_geckolib::jsstring_to_str;
 use util::prefs;
+use util::str::DOMString;
 
 /// Proxy handler for a WindowProxy.
 pub struct WindowProxyHandler(pub *const libc::c_void);
@@ -182,18 +183,18 @@ pub fn get_array_index_from_id(_cx: *mut JSContext, id: HandleId) -> Option<u32>
 
 /// Find the index of a string given by `v` in `values`.
 /// Returns `Err(())` on JSAPI failure (there is a pending exception), and
-/// `Ok(None)` if there was no matching string.
+/// `Ok((None, value))` if there was no matching string.
 pub unsafe fn find_enum_string_index(cx: *mut JSContext,
                                      v: HandleValue,
                                      values: &[&'static str])
-                                     -> Result<Option<usize>, ()> {
+                                     -> Result<(Option<usize>, DOMString), ()> {
     let jsstr = ToString(cx, v);
     if jsstr.is_null() {
         return Err(());
     }
 
     let search = jsstring_to_str(cx, jsstr);
-    Ok(values.iter().position(|value| search == *value))
+    Ok((values.iter().position(|value| search == *value), search))
 }
 
 /// Returns wether `obj` is a platform object